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1.  Clinical and economic consequences of hospital-acquired resistant and multidrug-resistant Pseudomonas aeruginosa infections: a systematic review and meta-analysis 
Increasing rates of resistant and multidrug-resistant (MDR) P. aeruginosa in hospitalized patients constitute a major public health threat. We present a systematic review of the clinical and economic impact of this resistant pathogen.
Studies indexed in MEDLINE and Cochrane databases between January 2000-February 2013, and reported all-cause mortality, length of stay, hospital costs, readmission, or recurrence in at least 20 hospitalized patients with laboratory confirmed resistant P. aeruginosa infection were included. We accepted individual study definitions of MDR, and assessed study methodological quality.
The most common definition of MDR was resistance to more than one agent in three or more categories of antibiotics. Twenty-three studies (7,881 patients with susceptible P. aeruginosa, 1,653 with resistant P. aeruginosa, 559 with MDR P. aeruginosa, 387 non-infected patients without P. aeruginosa) were analyzed. A random effects model meta-analysis was feasible for the endpoint of all-cause in-hospital mortality. All-cause mortality was 34% (95% confidence interval (CI) 27% – 41%) in patients with any resistant P. aeruginosa compared to 22% (95% CI 14% – 29%) with susceptible P. aeruginosa. The meta-analysis demonstrated a > 2-fold increased risk of mortality with MDR P. aeruginosa (relative risk (RR) 2.34, 95% CI 1.53 – 3.57) and a 24% increased risk with resistant P. aeruginosa (RR 1.24, 95% CI 1.11 – 1.38), compared to susceptible P. aeruginosa. An adjusted meta-analysis of data from seven studies demonstrated a statistically non-significant increased risk of mortality in patients with any resistant P. aeruginosa (adjusted RR 1.24, 95% CI 0.98 – 1.57). All three studies that reported infection-related mortality found a statistically significantly increased risk in patients with MDR P. aeruginosa compared to those with susceptible P. aeruginosa. Across studies, hospital length of stay (LOS) was higher in patients with resistant and MDR P. aeruginosa infections, compared to susceptible P. aeruginosa and control patients. Limitations included heterogeneity in MDR definition, restriction to nosocomial infections, and potential confounding in analyses.
Hospitalized patients with resistant and MDR P. aeruginosa infections appear to have increased all-cause mortality and LOS. The negative clinical and economic impact of these pathogens warrants in-depth evaluation of optimal infection prevention and stewardship strategies.
Electronic supplementary material
The online version of this article (doi:10.1186/2047-2994-3-32) contains supplementary material, which is available to authorized users.
PMCID: PMC4219028  PMID: 25371812
Pseudomonas aeruginosa; Resistance; All-cause mortality
2.  Prevalence, Resistance Mechanisms, and Susceptibility of Multidrug-Resistant Bloodstream Isolates of Pseudomonas aeruginosa▿  
Pseudomonas aeruginosa is an important pathogen commonly implicated in nosocomial infections. The occurrence of multidrug-resistant (MDR) P. aeruginosa strains is increasing worldwide and limiting our therapeutic options. The MDR phenotype can be mediated by a variety of resistance mechanisms, and the corresponding relative biofitness is not well established. We examined the prevalence, resistance mechanisms, and susceptibility of MDR P. aeruginosa isolates (resistant to ≥3 classes of antipseudomonal agents [penicillins/cephalosporins, carbapenems, quinolones, and aminoglycosides]) obtained from a large, university-affiliated hospital. Among 235 nonrepeat bloodstream isolates screened between 2005 and 2007, 33 isolates (from 20 unique patients) were found to be MDR (crude prevalence rate, 14%). All isolates were resistant to carbapenems and quinolones, 91% were resistant to penicillins/cephalosporins, and 21% were resistant to the aminoglycosides. By using the first available isolate for each bacteremia episode (n = 18), 13 distinct clones were revealed by repetitive-element-based PCR. Western blotting revealed eight isolates (44%) to have MexB overexpression. Production of a carbapenemase (VIM-2) was found in one isolate, and mutations in gyrA (T83I) and parC (S87L) were commonly found. Growth rates of most MDR isolates were similar to that of the wild type, and two isolates (11%) were found to be hypermutable. All available isolates were susceptible to polymyxin B, and only one isolate was nonsusceptible to colistin (MIC, 3 mg/liter), but all isolates were nonsusceptible to doripenem (MIC, >2 mg/liter). Understanding and continuous monitoring of the prevalence and resistance mechanisms of MDR P. aeruginosa would enable us to formulate rational treatment strategies to combat nosocomial infections.
PMCID: PMC2826008  PMID: 20086165
3.  Additional risk factors for infection by multidrug-resistant pathogens in healthcare-associated infection: a large cohort study 
BMC Infectious Diseases  2012;12:375.
There is a lack of consensus regarding the definition of risk factors for healthcare-associated infection (HCAI). The purpose of this study was to identify additional risk factors for HCAI, which are not included in the current definition of HCAI, associated with infection by multidrug-resistant (MDR) pathogens, in all hospitalized infected patients from the community.
This 1-year prospective cohort study included all patients with infection admitted to a large, tertiary care, university hospital. Risk factors not included in the HCAI definition, and independently associated with MDR pathogen infection, namely MDR Gram-negative (MDR-GN) and ESKAPE microorganisms (vancomycin-resistant Enterococcus faecium, methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella species, carbapenem-hydrolyzing Klebsiella pneumonia and MDR Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species), were identified by logistic regression among patients admitted from the community (either with community-acquired or HCAI).
There were 1035 patients with infection, 718 from the community. Of these, 439 (61%) had microbiologic documentation; 123 were MDR (28%). Among MDR: 104 (85%) had MDR-GN and 41 (33%) had an ESKAPE infection. Independent risk factors associated with MDR and MDR-GN infection were: age (adjusted odds ratio (OR) = 1.7 and 1.5, p = 0.001 and p = 0.009, respectively), and hospitalization in the previous year (between 4 and 12 months previously) (adjusted OR = 2.0 and 1,7, p = 0.008 and p = 0.048, respectively). Infection by pathogens from the ESKAPE group was independently associated with previous antibiotic therapy (adjusted OR = 7.2, p < 0.001) and a Karnofsky index <70 (adjusted OR = 3.7, p = 0.003). Patients with infection by MDR, MDR-GN and pathogens from the ESKAPE group had significantly higher rates of inadequate antibiotic therapy than those without (46% vs 7%, 44% vs 10%, 61% vs 15%, respectively, p < 0.001).
This study suggests that the inclusion of additional risk factors in the current definition of HCAI for MDR pathogen infection, namely age >60 years, Karnofsky index <70, hospitalization in the previous year, and previous antibiotic therapy, may be clinically beneficial for early diagnosis, which may decrease the rate of inadequate antibiotic therapy among these patients.
PMCID: PMC3566942  PMID: 23267668
Healthcare-associated infections; Multidrug resistant pathogens infection; Multidrug resistant gram negatives infection; ESKAPE microorganisms’ infection; Independent risk factors; Inadequate antibiotic therapy
4.  Clinical Prediction Tool To Identify Patients with Pseudomonas aeruginosa Respiratory Tract Infections at Greatest Risk for Multidrug Resistance▿  
Despite the increasing prevalence of multiple-drug-resistant (MDR) Pseudomonas aeruginosa, the factors predictive of MDR have not been extensively explored. We sought to examine factors predictive of MDR among patients with P. aeruginosa respiratory tract infections and to develop a tool to estimate the probability of MDR among such high-risk patients. This was a single-site, case-control study of patients with P. aeruginosa respiratory tract infections. Multiple-drug resistance was defined as resistance to four or more antipseudomonal antimicrobial classes. Clinical data on demographics, antibiotic history, and microbiology were collected. Classification and regression tree analysis (CART) was used to identify the duration of antibiotic exposure associated with MDR P. aeruginosa. Log-binomial regression was used to model the probability of MDR P. aeruginosa. Among 351 P. aeruginosa-infected patients, the proportion of MDR P. aeruginosa was 35%. A significant relationship between prior antibiotic exposure and MDR P. aeruginosa was found for all of the antipseudomonal antibiotics studied, but the duration of prior exposure associated with MDR varied between antibiotic classes; the shortest prior exposure duration was observed for carbapenems and fluoroquinolones, and the longest duration was noted for cefepime and piperacillin-tazobactam. Within the final model, the predicted MDR P. aeruginosa likelihood was most dependent upon length of hospital stay, prior culture sample collection, and number of CART-derived prior antibiotic exposures. A history of a prolonged hospital stay and exposure to antipseudomonal antibiotics predicts multidrug resistance among patients with P. aeruginosa respiratory tract infections at our institution. Identifying these risk factors enabled us to develop a prediction tool to assess the risk of resistance and thus guide empirical antibiotic therapy.
PMCID: PMC1797724  PMID: 17158943
5.  Carbapenemase Genes among Multidrug Resistant Gram Negative Clinical Isolates from a Tertiary Hospital in Mwanza, Tanzania 
BioMed Research International  2014;2014:303104.
The burden of antimicrobial resistance (AMR) is rapidly growing across antibiotic classes, with increased detection of isolates resistant to carbapenems. Data on the prevalence of carbapenem resistance in developing countries is limited; therefore, in this study, we determined the prevalence of carbapenemase genes among multidrug resistant gram negative bacteria (MDR-GNB) isolated from clinical specimens in a tertiary hospital in Mwanza, Tanzania. A total of 227 MDR-GNB isolates were analyzed for carbapenem resistance genes. For each isolate, five different PCR assays were performed, allowing for the detection of the major carbapenemase genes, including those encoding the VIM-, IMP-, and NDM-type metallo-beta-lactamases, the class A KPC-type carbapenemases, and the class D OXA-48 enzyme. Of 227 isolates, 80 (35%) were positive for one or more carbapenemase gene. IMP-types were the most predominant gene followed by VIM, in 49 (21.59%) and 28 (12%) isolates, respectively. Carbapenemase genes were most detected in K. pneumoniae 24 (11%), followed by P. aeruginosa 23 (10%), and E. coli with 19 isolates (8%). We have demonstrated for the first time a high prevalence of MDR-GNB clinical isolates having carbapenem resistance genes in Tanzania. We recommend routine testing for carbapenem resistance among the MDR-GNB particularly in systemic infections.
PMCID: PMC3953670  PMID: 24707481
6.  Multidrug Resistant Pulmonary Tuberculosis Treatment Regimens and Patient Outcomes: An Individual Patient Data Meta-analysis of 9,153 Patients 
Ahuja, Shama D. | Ashkin, David | Avendano, Monika | Banerjee, Rita | Bauer, Melissa | Bayona, Jamie N. | Becerra, Mercedes C. | Benedetti, Andrea | Burgos, Marcos | Centis, Rosella | Chan, Eward D. | Chiang, Chen-Yuan | Cox, Helen | D'Ambrosio, Lia | DeRiemer, Kathy | Dung, Nguyen Huy | Enarson, Donald | Falzon, Dennis | Flanagan, Katherine | Flood, Jennifer | Garcia-Garcia, Maria L. | Gandhi, Neel | Granich, Reuben M. | Hollm-Delgado, Maria G. | Holtz, Timothy H. | Iseman, Michael D. | Jarlsberg, Leah G. | Keshavjee, Salmaan | Kim, Hye-Ryoun | Koh, Won-Jung | Lancaster, Joey | Lange, Christophe | de Lange, Wiel C. M. | Leimane, Vaira | Leung, Chi Chiu | Li, Jiehui | Menzies, Dick | Migliori, Giovanni B. | Mishustin, Sergey P. | Mitnick, Carole D. | Narita, Masa | O'Riordan, Philly | Pai, Madhukar | Palmero, Domingo | Park, Seung-kyu | Pasvol, Geoffrey | Peña, Jose | Pérez-Guzmán, Carlos | Quelapio, Maria I. D. | Ponce-de-Leon, Alfredo | Riekstina, Vija | Robert, Jerome | Royce, Sarah | Schaaf, H. Simon | Seung, Kwonjune J. | Shah, Lena | Shim, Tae Sun | Shin, Sonya S. | Shiraishi, Yuji | Sifuentes-Osornio, José | Sotgiu, Giovanni | Strand, Matthew J. | Tabarsi, Payam | Tupasi, Thelma E. | van Altena, Robert | Van der Walt, Martie | Van der Werf, Tjip S. | Vargas, Mario H. | Viiklepp, Pirett | Westenhouse, Janice | Yew, Wing Wai | Yim, Jae-Joon
PLoS Medicine  2012;9(8):e1001300.
Dick Menzies and colleagues report findings from a collaborative, individual patient-level meta-analysis of treatment outcomes among patients with multidrug-resistant tuberculosis.
Treatment of multidrug resistant tuberculosis (MDR-TB) is lengthy, toxic, expensive, and has generally poor outcomes. We undertook an individual patient data meta-analysis to assess the impact on outcomes of the type, number, and duration of drugs used to treat MDR-TB.
Methods and Findings
Three recent systematic reviews were used to identify studies reporting treatment outcomes of microbiologically confirmed MDR-TB. Study authors were contacted to solicit individual patient data including clinical characteristics, treatment given, and outcomes. Random effects multivariable logistic meta-regression was used to estimate adjusted odds of treatment success. Adequate treatment and outcome data were provided for 9,153 patients with MDR-TB from 32 observational studies. Treatment success, compared to failure/relapse, was associated with use of: later generation quinolones, (adjusted odds ratio [aOR]: 2.5 [95% CI 1.1–6.0]), ofloxacin (aOR: 2.5 [1.6–3.9]), ethionamide or prothionamide (aOR: 1.7 [1.3–2.3]), use of four or more likely effective drugs in the initial intensive phase (aOR: 2.3 [1.3–3.9]), and three or more likely effective drugs in the continuation phase (aOR: 2.7 [1.7–4.1]). Similar results were seen for the association of treatment success compared to failure/relapse or death: later generation quinolones, (aOR: 2.7 [1.7–4.3]), ofloxacin (aOR: 2.3 [1.3–3.8]), ethionamide or prothionamide (aOR: 1.7 [1.4–2.1]), use of four or more likely effective drugs in the initial intensive phase (aOR: 2.7 [1.9–3.9]), and three or more likely effective drugs in the continuation phase (aOR: 4.5 [3.4–6.0]).
In this individual patient data meta-analysis of observational data, improved MDR-TB treatment success and survival were associated with use of certain fluoroquinolones, ethionamide, or prothionamide, and greater total number of effective drugs. However, randomized trials are urgently needed to optimize MDR-TB treatment.
Please see later in the article for the Editors' Summary.
Editors' Summary
In 2010, 8.8 million people developed tuberculosis—a contagious bacterial infection—and 1.4 million people died from the disease. Mycobacterium tuberculosis, the bacterium that causes tuberculosis, is spread in airborne droplets when people with the disease cough or sneeze and usually infects the lungs (pulmonary tuberculosis). The characteristic symptoms of tuberculosis are a persistent cough, weight loss, and night sweats. Tuberculosis can be cured by taking several powerful antibiotics regularly for at least 6 months. The standard treatment for tuberculosis comprises an initial intensive phase lasting 2 months during which four antibiotics are taken daily followed by a 4-month continuation phase during which two antibiotics are taken. However, global efforts to control tuberculosis are now being thwarted by the emergence of M. tuberculosis strains that are resistant to several antibiotics, including isoniazid and rifampicin, the two most powerful, first-line (standard) anti-tuberculosis drugs.
Why Was This Study Done?
Although multi-drug resistant tuberculosis (MDR-TB) can be cured using second-line anti-tuberculosis drugs, these are more expensive and more toxic than first-line drugs and optimal treatment regimens for MDR-TB have not been determined. Notably, there have been no randomized controlled trials of treatments for MDR-TB. Such trials, which compare outcomes (cure, treatment failure, relapse, and death) among patients who have been randomly assigned to receive different treatments, are the best way to compare different anti-tuberculosis drug regimens. It is possible, however, to get useful information about the association of various treatments for MDR-TB with outcomes from observational studies using a statistical approach called “individual patient data meta-analysis.” In observational studies, because patients are not randomly assigned to different treatments, differences in outcomes between treatment groups may not be caused by the different drugs they receive but may be due to other differences between the groups. An individual patient data meta-analysis uses statistical methods to combine original patient data from several different studies. Here, the researchers use this approach to investigate the association of specific drugs, numbers of drugs and treatment duration with the clinical outcomes of patients with pulmonary MDR-TB.
What Did the Researchers Do and Find?
The researchers used three recent systematic reviews (studies that use predefined criteria to identify all the research on a given topic) to identify studies reporting treatment outcomes of microbiologically confirmed MDR-TB. They obtained individual patient data from the authors of these studies and estimated adjusted odds (chances) of treatment success from the treatment and outcome data of 9,153 patients with MDR-TB provided by 32 centers. The use of later generation quinolones, ofloxacin, and ethionamide/prothionamide as part of multi-drug regimens were all associated with treatment success compared to failure, relapse or death, as were the use of four or more likely effective drugs (based on drug susceptibility testing of mycobacteria isolated from study participants) during the initial intensive treatment phase and the use of three or more likely effective drugs during the continuation phase. The researchers also report that among patients who did not die or stop treatment, the chances of treatment success increased with the duration of the initial treatment phase up to 7.1–8.5 months and with the total duration of treatment up to 18.6–21.5 months.
What Do These Findings Mean?
These findings suggest that the use of specific drugs, the use of a greater number of effective drugs, and longer treatments may be associated with treatment success and the survival of patients with MDR-TR. However, these findings need to be interpreted with caution because of limitations in this study that may have affected the accuracy of its findings. For example, the researchers did not include all the studies they found through the systematic reviews in their meta-analysis (some authors did not respond to requests for individual patient data, for example), which may have introduced bias. Moreover, because the patients included in the meta-analysis were treated at 32 centers, there were many differences in their management, some of which may have affected the accuracy of the findings. Because of these and other limitations, the researchers note that, although their findings highlight several important questions about the treatment of MDR-TB, randomized controlled trials are urgently needed to determine the optimal treatment for MDR-TB.
Additional Information
Please access these Web sites via the online version of this summary at
The World Health Organization provides information on all aspects of tuberculosis, including MDR-TB; its guidelines for the programmatic management of drug-resistant tuberculosis are available
The US Centers for Disease Control and Prevention has information about tuberculosis, including information on the treatment of tuberculosis and on MDR-TB
The US National Institute of Allergy and Infectious Diseases also has information on all aspects of tuberculosis, including a drug-resistant tuberculosis visual tour
MedlinePlus has links to further information about tuberculosis (in English and Spanish)
TB & ME, a collaborative blogging project run by patients being treated for multidrug-resistant tuberculosis and Medecins sans Frontieres, provides information about MDR-TB and patient stories about treatment for MDR-TB
The Tuberculosis Survival Project, which aims to raise awareness of tuberculosis and provide support for people with tuberculosis, also provides personal stories about treatment for tuberculosis
PMCID: PMC3429397  PMID: 22952439
7.  Feasibility and Cost-Effectiveness of Treating Multidrug-Resistant Tuberculosis: A Cohort Study in the Philippines 
PLoS Medicine  2006;3(9):e352.
Multidrug-resistant tuberculosis (MDR-TB) is an important global health problem, and a control strategy known as DOTS-Plus has existed since 1999. However, evidence regarding the feasibility, effectiveness, cost, and cost-effectiveness of DOTS-Plus is still limited.
Methodology/Principal Findings
We evaluated the feasibility, effectiveness, cost, and cost-effectiveness of a DOTS-Plus pilot project established at Makati Medical Center in Manila, the Philippines, in 1999. Patients with MDR-TB are treated with regimens, including first- and second-line drugs, tailored to their drug susceptibility pattern (i.e., individualised treatment). We considered the cohort enrolled between April 1999 and March 2002. During this three-year period, 118 patients were enrolled in the project; 117 were considered in the analysis. Seventy-one patients (61%) were cured, 12 (10%) failed treatment, 18 (15%) died, and 16 (14%) defaulted. The average cost per patient treated was US$3,355 from the perspective of the health system, of which US$1,557 was for drugs, and US$837 from the perspective of patients. The mean cost per disability-adjusted life year (DALY) gained by the DOTS-Plus project was US$242 (range US$85 to US$426).
Treatment of patients with MDR-TB using the DOTS-Plus strategy and individualised drug regimens can be feasible, comparatively effective, and cost-effective in low- and middle-income countries.
Evaluation of 117 patients enrolled in a DOTS-Plus pilot project in the Philippines showed that in this setting the strategy is feasible.
Editors' Summary
Tuberculosis (TB) causes the death of some 2 million people each year. An estimated one in three people worldwide are infected with Mycobacterium tuberculosis, the bacterium that causes the disease. Because single-drug treatment leads to treatment failure and antibiotic resistance, treatment for active TB is complicated, usually involving four different antibiotics, at least two of which are continued for six months or more. The World Health Organization (WHO) recommends a specific strategy (DOTS) for diagnosing and treating TB (see Web link below).
The DOTS approach includes standard regimens of first-line drugs which cure about 90% of patients with drug-susceptible TB, and which cost as little as US$10 per patient. Unfortunately, TB resistance to at least two of the most effective DOTS drugs has developed at sites in both industrialized and developing countries, causing approximately 460,000 cases of multidrug-resistant TB (MDR-TB) per year. Second-line antibiotics, which tend to be more expensive or more difficult to take, can effectively treat many cases of MDR-TB. “DOTS-Plus” programmes, which use combinations of first- and second-line drugs to treat MDR-TB, are therefore becoming increasingly important in controlling TB worldwide. A recent study found DOTS-Plus strategies to be cost-effective in Peru, but cure rates of MDR-TB were relatively low.
Why Was This Study Done?
Because the use of second-line antibiotics is costly and the treatment of MDR-TB has a higher failure rate than that of fully drug-susceptible TB, policymakers responsible for allocation of limited healthcare resources need information on how well DOTS-Plus programmes work and how much they cost to operate. This study was undertaken to assess the feasibility, effectiveness, and cost-effectiveness of a DOTS-Plus project in the Philippines, a lower middle–income country with a high rate of TB and approximately 25,000 cases of MDR-TB.
What Did the Researchers Do and Find? 
The researchers reported on a DOTS-Plus pilot project at Makati Medical Center in Manila, analyzing information from 118 patients enrolled in the project between 1999 and 2002. The diagnosis of MDR-TB was based on laboratory culture and antibiotic resistance testing of specimens from patients who had continued symptoms of TB following DOTS treatment, or other evidence of possible MDR-TB. Patients were treated with five-drug combinations individually selected based on resistance testing results, and administered under direct observation. After cultures had remained consistently negative for six months, patients were switched to a four-drug regimen with intermittent clinic observation until cultures remained negative for at least 18 months.
Cost-effectiveness was assessed by comparing the costs and effects of the project to the costs and effects that would have applied in the absence of the project, namely, no treatment of MDR-TB (except what patients could have purchased privately), or standard first-line DOTS treatment (which would not cure the majority of patients with MDR-TB, and is associated with a high chance of relapse in those who do appear cured). Costs of the DOTS-Plus project were based on expenditure records, project records, and interviews with staff, patients, and funding agencies. Effects of the project were based on treatment outcomes observed among enrolled patients, as well as on data on long-term outcomes among patients treated for MDR-TB in the US who were followed for up to ten years. Treatment costs for the situation in which no DOTS-Plus project exists were estimated using national data reported to WHO, as well as questionnaires administered to local patients in whom DOTS treatment had failed. Treatment outcomes where DOTS-Plus is not available were estimated from studies done in other TB-affected countries.
The researchers found that the cure rate of MDR-TB in this project was 61%. The cost per patient treated was US$4,192. They also calculated that the cost-effectiveness of the DOTS-Plus strategy was US$242 per disability-adjusted life year (DALY) gained, of which US$179 was paid by the healthcare system.
What Do These Findings Mean?
The cure rate for MDR-TB in this project compares favourably to rates in other resource-limited settings where second-line TB drugs are used, and is much higher than in areas where these drugs are not available. From the standpoint of efficacy and patient well-being, then, this study supports the necessity of DOTS-Plus treatment. In purely economic terms, the cost of US$200–US$250 per DALY gained is cost-effective in comparison with other healthcare interventions. Specifically, because the gross national income per person in the Philippines is US$1,080, someone who can return to work following MDR-TB treatment costing US$250 per year gained of working life will provide work that is worth four times more, on average, than the cost of the treatment.
Although this study provides encouraging confirmation that DOTS-Plus programmes can be effective and cost-effective in a resource-limited setting, these findings are subject to several limitations. First, the data used to estimate treatment outcomes and the costs associated with chronic MDR-TB when DOTS-Plus treatment is not available were limited. Also, the pilot project in this study included only 118 of 171 eligible patients, leaving open the possibility that the other 53 patients might have had different outcomes. In addition, the long-term relapse rate in the treated patients is unknown. Finally, the conclusion that one model programme is effective does not mean that other programmes will do well under less favourable circumstances. Nonetheless, as MDR-TB continues to spread in the developing world, a good example is good news. A Perspective by Paul Garner and colleagues in this issue of PLoS Medicine (DOI: 10.1371/journal.pmed.0030350) discusses the study further.
Additional Information. 
Please access these Web sites via the online version of this summary at
Basic information about tuberculosis can be found on the Web site of the US National Institute of Allergy and Infectious Diseases (NIAID)
The Web site of the World Health Organization's Stop TB department outlines both the DOTS and DOTS-Plus strategies
TB Alert, a UK-based charity that promotes TB awareness worldwide, has information on TB in several European, African, and Asian languages
PMCID: PMC1564168  PMID: 16968123
8.  Cost-Effectiveness of Treating Multidrug-Resistant Tuberculosis 
PLoS Medicine  2006;3(7):e241.
Despite the existence of effective drug treatments, tuberculosis (TB) causes 2 million deaths annually worldwide. Effective treatment is complicated by multidrug-resistant TB (MDR TB) strains that respond only to second-line drugs. We projected the health benefits and cost-effectiveness of using drug susceptibility testing and second-line drugs in a lower-middle-income setting with high levels of MDR TB.
Methods and Findings
We developed a dynamic state-transition model of TB. In a base case analysis, the model was calibrated to approximate the TB epidemic in Peru, a setting with a smear-positive TB incidence of 120 per 100,000 and 4.5% MDR TB among prevalent cases. Secondary analyses considered other settings. The following strategies were evaluated: first-line drugs administered under directly observed therapy (DOTS), locally standardized second-line drugs for previously treated cases (STR1), locally standardized second-line drugs for previously treated cases with test-confirmed MDR TB (STR2), comprehensive drug susceptibility testing and individualized treatment for previously treated cases (ITR1), and comprehensive drug susceptibility testing and individualized treatment for all cases (ITR2). Outcomes were costs per TB death averted and costs per quality-adjusted life year (QALY) gained. We found that strategies incorporating the use of second-line drug regimens following first-line treatment failure were highly cost-effective compared to strategies using first-line drugs only. In our base case, standardized second-line treatment for confirmed MDR TB cases (STR2) had an incremental cost-effectiveness ratio of $720 per QALY ($8,700 per averted death) compared to DOTS. Individualized second-line drug treatment for MDR TB following first-line failure (ITR1) provided more benefit at an incremental cost of $990 per QALY ($12,000 per averted death) compared to STR2. A more aggressive version of the individualized treatment strategy (ITR2), in which both new and previously treated cases are tested for MDR TB, had an incremental cost-effectiveness ratio of $11,000 per QALY ($160,000 per averted death) compared to ITR1. The STR2 and ITR1 strategies remained cost-effective under a wide range of alternative assumptions about treatment costs, effectiveness, MDR TB prevalence, and transmission.
Treatment of MDR TB using second-line drugs is highly cost-effective in Peru. In other settings, the attractiveness of strategies using second-line drugs will depend on TB incidence, MDR burden, and the available budget, but simulation results suggest that individualized regimens would be cost-effective in a wide range of situations.
Editors' Summary
Tuberculosis (TB) remains one of the most entrenched diseases on the planet—an estimated one in three people worldwide are infected with Mycobacterium tuberculosis, which causes the disease. Although effective drugs exist, a major reason for the failure to stem the spread of TB lies in the rise of drug-resistant strains of the bacterium. Some strains are resistant to several drugs; patients with this sort of infection are said to have multidrug-resistant (MDR) TB. The development of drug-resistant strains is fostered when health-care workers do not follow treatment guidelines or fail to ensure that patients take the whole treatment course. The World Health Organization recommends an approach to TB control called “DOTS,” which has been adopted by many countries. (See the link below for an explanation of what DOTS involves.) The antibiotics that are used in DOTS are described as “first-line” treatment drugs. They are highly effective against non-resistant TB but much less so against MDR TB. There are other, more expensive, “second-line” antibiotics that perform better against MDR TB.
  Why Was This Study Done?
Despite the worrying rise in MDR TB cases, the much higher cost of using second-line drugs is prompting some policy-makers to question the merits of introducing them in poor countries with limited resources. However, with MDR TB accounting for nearly a third of TB cases in some countries, first-line therapies seem unlikely to be sufficient in the long term. Second-line strategies, or “DOTS-Plus” strategies, are either standardized for a particular region or are chosen for individual patients on the basis of drug susceptibility tests. The researchers wanted to investigate whether standardized or individualized second-line regimens could save lives and be cost-effective in poor countries.
  What Did the Researchers Do and Find?
The researchers used a method called modeling. They took information already available about TB in Peru, where for every 100,000 people there are 120 new TB infections every year, and 4.5% of existing cases are MDR TB. The researchers then calculated what might happen over the next 30 years, comparing the likely effects of five alternative strategies. In four, new cases were given first-line drugs for 6 months. Those who were not cured were then treated in different ways. In DOTS, they were retreated with a second course of the same drugs; in STR1 they were given an 18-month standardized course of second-line and first-line drugs; in STR2, only confirmed MDR TB patients were given an 18-month standardized course of second-line and first-line drugs; and in ITR1, confirmed MDR TB patients were given a personalized regimen of second-line drugs. The fifth strategy, ITR2, tested all patients for drug susceptibility at the outset of treatment, and those with MDR TB were given an individualized course; those not cured were tested again and given another individualized course.
  Compared with DOTS, both the STR1 and STR2 strategies averted 4.8 deaths per 100,000 population, at a cost of $8,700 per averted death—with STR2 being a better value for money since it treated only confirmed MDR TB cases with the more expensive, second-line drugs. Of the individualized treatments, ITR1 averted an extra 0.9 deaths at a cost of $12,000 per averted death; ITR2 averted a further 1.2 deaths but at a much higher $160,000 per saved life.
  What Do These Findings Mean?
Despite the slightly higher cost of ITR1, the extra number of lives it would save compared with STR2 makes it a good approach for treatment in Peru. However, cost-effectiveness varies with other factors. If the difference in cost between the two strategies became higher than $9,500 per patient, STR would be preferable. And, if MDR TB were present in 10% of all TB cases, ITR2—with comprehensive drug susceptibility testing for all TB patients—would be best.
  The findings are of interest not just in Peru but in other developing countries where MDR TB is a growing problem. The researchers maintain that, in areas where DOTS has not yet been fully implemented, it would be more efficient to expand DOTS than to introduce DOTS-Plus. But they add that it would be beneficial to expand DOTS as well as implement DOTS-Plus. Individualized treatment after drug susceptibility testing is likely to be cost-effective even in the poorest of countries, which should give impetus to governments and organizations in those countries where MDR TB is a growing concern to modify their approach to treatment.
  Additional Information.
Please access these Web sites via the online version of this summary at
• Basic information about tuberculosis can be found on the Web site of the US National Institute of Allergy and Infectious Diseases
• The Web site of the World Health Organization's Stop TB department outlines both the DOTS and DOTS-Plus strategies
•  TB Alert, a UK-based charity that promotes TB awareness worldwide, has information on TB in several European, African, and Asian languages
Resch and colleagues found that treatment of MDR TB using second-line drugs is highly cost-effective in Peru.
PMCID: PMC1483913  PMID: 16796403
9.  Multidrug-Resistant Pseudomonas aeruginosa: Risk Factors and Clinical Impact†  
Pseudomonas aeruginosa, a leading nosocomial pathogen, may become multidrug resistant (MDR). Its rate of occurrence, the individual risk factors among affected patients, and the clinical impact of infection are undetermined. We conducted an epidemiologic evaluation and molecular typing using pulsed-field gel electrophoresis (PFGE) of 36 isolates for 82 patients with MDR P. aeruginosa and 82 controls matched by ward, length of hospital stay, and calendar time. A matched case-control study identified individual risk factors for having MDR P. aeruginosa, and a retrospective matched-cohort study examined clinical outcomes of such infections. The 36 isolates belonged to 12 PFGE clones. Two clones dominated, with one originating in an intensive care unit (ICU). Cases and controls had similar demographic characteristics and numbers of comorbid conditions. A multivariate model identified ICU stay, being bedridden, having high invasive devices scores, and being treated with broad-spectrum cephalosporins and with aminoglycosides as significant risk factors for isolating MDR P. aeruginosa. Having a malignant disease was a protective factor (odds ratio [OR] = 0.2; P = 0.03). MDR P. aeruginosa was associated with severe outcomes compared to controls, including increased mortality (OR = 4.4; P = 0.04), hospital stay (hazard ratio, 2; P = 0.001), and requirement for procedures (OR = 5.4; P = 0.001). The survivors functioned more poorly at discharge than the controls, and more of the survivors were discharged to rehabilitation centers or chronic care facilities. The epidemiology of MDR P. aeruginosa is complex. Critically ill patients that require intensive care and are treated with multiple antibiotic agents are at high risk. MDR P. aeruginosa infections are associated with severe adverse clinical outcomes.
PMCID: PMC1346794  PMID: 16377665
10.  Screening and Rapid Molecular Diagnosis of Tuberculosis in Prisons in Russia and Eastern Europe: A Cost-Effectiveness Analysis 
PLoS Medicine  2012;9(11):e1001348.
Daniel Winetsky and colleagues investigate eight strategies for screening and diagnosis of tuberculosis within prisons of the former Soviet Union.
Prisons of the former Soviet Union (FSU) have high rates of multidrug-resistant tuberculosis (MDR-TB) and are thought to drive general population tuberculosis (TB) epidemics. Effective prison case detection, though employing more expensive technologies, may reduce long-term treatment costs and slow MDR-TB transmission.
Methods and Findings
We developed a dynamic transmission model of TB and drug resistance matched to the epidemiology and costs in FSU prisons. We evaluated eight strategies for TB screening and diagnosis involving, alone or in combination, self-referral, symptom screening, mass miniature radiography (MMR), and sputum PCR with probes for rifampin resistance (Xpert MTB/RIF). Over a 10-y horizon, we projected costs, quality-adjusted life years (QALYs), and TB and MDR-TB prevalence. Using sputum PCR as an annual primary screening tool among the general prison population most effectively reduced overall TB prevalence (from 2.78% to 2.31%) and MDR-TB prevalence (from 0.74% to 0.63%), and cost US$543/QALY for additional QALYs gained compared to MMR screening with sputum PCR reserved for rapid detection of MDR-TB. Adding sputum PCR to the currently used strategy of annual MMR screening was cost-saving over 10 y compared to MMR screening alone, but produced only a modest reduction in MDR-TB prevalence (from 0.74% to 0.69%) and had minimal effect on overall TB prevalence (from 2.78% to 2.74%). Strategies based on symptom screening alone were less effective and more expensive than MMR-based strategies. Study limitations included scarce primary TB time-series data in FSU prisons and uncertainties regarding screening test characteristics.
In prisons of the FSU, annual screening of the general inmate population with sputum PCR most effectively reduces TB and MDR-TB prevalence, doing so cost-effectively. If this approach is not feasible, the current strategy of annual MMR is both more effective and less expensive than strategies using self-referral or symptom screening alone, and the addition of sputum PCR for rapid MDR-TB detection may be cost-saving over time.
Please see later in the article for the Editors' Summary
Editors' Summary
Tuberculosis (TB)—a contagious bacterial disease—is a major public health problem, particularly in low- and middle-income countries. In 2010, about nine million people developed TB, and about 1.5 million people died from the disease. Mycobacterium tuberculosis, the bacterium that causes TB, is spread in airborne droplets when people with active disease cough or sneeze. The characteristic symptoms of TB include fever, a persistent cough, and night sweats. Diagnostic tests include sputum smear microscopy (examination of mucus from the lungs for M. tuberculosis bacilli), mycobacterial culture (growth of M. tuberculosis from sputum), and chest X-rays. TB can also be diagnosed by looking for fragments of the M. tuberculosis genetic blueprint in sputum samples (sputum PCR). Importantly, sputum PCR can detect the genetic changes that make M. tuberculosis resistant to rifampicin, a constituent of the cocktail of antibiotics that is used to cure TB. Rifampicin resistance is an indicator of multidrug-resistant TB (MDR-TB), the emergence of which is thwarting ongoing global efforts to control TB.
Why Was This Study Done?
Prisons present unique challenges for TB control. Overcrowding, poor ventilation, and inadequate medical care increase the spread of TB among prisoners, who often come from disadvantaged populations where the prevalence of TB (the proportion of the population with TB) is already high. Prisons also act as reservoirs for TB, recycling the disease back into the civilian population. The prisons of the former Soviet Union, for example, which have extremely high rates of MDR-TB, are thought to drive TB epidemics in the general population. Because effective identification of active TB among prison inmates has the potential to improve TB control outside prisons, the World Health Organization recommends active TB case finding among prisoners using self-referral, screening with symptom questionnaires, or screening with chest X-rays or mass miniature radiography (MMR). But which of these strategies will reduce the prevalence of TB in prisons most effectively, and which is most cost-effective? Here, the researchers evaluate the relative effectiveness and cost-effectiveness of alternative strategies for screening and diagnosis of TB in prisons by modeling TB and MDR-TB epidemics in prisons of the former Soviet Union.
What Did the Researchers Do and Find?
The researchers used a dynamic transmission model of TB that simulates the movement of individuals in prisons in the former Soviet Union through different stages of TB infection to estimate the costs, quality-adjusted life years (QALYs; a measure of disease burden that includes both the quantity and quality of life) saved, and TB and MDR-TB prevalence for eight TB screening/diagnostic strategies over a ten-year period. Compared to annual MMR alone (the current strategy), annual screening with sputum PCR produced the greatest reduction in the prevalence of TB and of MDR-TB among the prison population. Adding sputum PCR for detection of MDR-TB to annual MMR screening did not affect the overall TB prevalence but slightly reduced the MDR-TB prevalence and saved nearly US$2,000 over ten years per model prison of 1,000 inmates, compared to MMR screening alone. Annual sputum PCR was the most cost-effective strategy, costing US$543/QALY for additional QALYs gained compared to MMR screening plus sputum PCR for MDR-TB detection. Other strategies tested, including symptom screening alone or combined with sputum PCR, were either more expensive and less effective or less cost-effective than these two options.
What Do These Findings Mean?
These findings suggest that, in prisons in the former Soviet Union, annual screening with sputum PCR will most effectively reduce TB and MDR-TB prevalence and will be cost-effective. That is, the cost per QALY saved of this strategy is less than the per-capita gross domestic product of any of the former Soviet Union countries. The paucity of primary data on some facets of TB epidemiology in prisons in the former Soviet Union and the assumptions built into the mathematical model limit the accuracy of these findings. Moreover, because most of the benefits of sputum PCR screening come from treating the MDR-TB cases that are detected using this screening approach, these findings cannot be generalized to prison settings without a functioning MDR-TB treatment program or with a very low MDR-TB prevalence. Despite these and other limitations, these findings provide valuable information about the screening strategies that are most likely to interrupt the TB cycle in prisons, thereby saving resources and averting preventable deaths both inside and outside prisons.
Additional Information
Please access these websites via the online version of this summary at
The World Health Organization provides information (in several languages) on all aspects of tuberculosis, including general information on tuberculosis diagnostics and on tuberculosis in prisons; a report published in the Bulletin of the World Health Organization in 2006 describes tough measures taken in Russian prisons to slow the spread of TB
The Stop TB Partnership is working towards tuberculosis elimination; patient stories about tuberculosis are available (in English and Spanish)
The US Centers for Disease Control and Prevention has information about tuberculosis, about its diagnosis, and about tuberculosis in prisons (some information in English and Spanish)
A PLOS Medicine Research Article by Iacapo Baussano et al. describes a systematic review of tuberculosis incidence in prisons; a linked editorial entitled The Health Crisis of Tuberculosis in Prisons Extends beyond the Prison Walls is also available
The Tuberculosis Survival Project, which aims to raise awareness of tuberculosis and provide support for people with tuberculosis, provides personal stories about treatment for tuberculosis; the Tuberculosis Vaccine Initiative also provides personal stories about dealing with tuberculosis
MedlinePlus has links to further information about tuberculosis (in English and Spanish)
PMCID: PMC3507963  PMID: 23209384
11.  Molecular Epidemiology and Mechanisms of Carbapenem Resistance in Pseudomonas aeruginosa Isolates from Spanish Hospitals▿  
Antimicrobial Agents and Chemotherapy  2007;51(12):4329-4335.
All (236) Pseudomonas aeruginosa isolates resistant to imipenem and/or meropenem collected during a multicenter (127-hospital) study in Spain were analyzed. Carbapenem-resistant isolates were found to be more frequently resistant to all β-lactams and non-β-lactam antibiotics than carbapenem-susceptible isolates (P < 0.001), and up to 46% of the carbapenem-resistant isolates met the criteria used to define multidrug resistance (MDR). Pulsed-field gel electrophoresis revealed remarkable clonal diversity (165 different clones were identified), and with few exceptions, the levels of intra- and interhospital dissemination of clones were found to be low. Carbapenem resistance was driven mainly by the mutational inactivation of OprD, accompanied or not by the hyperexpression of AmpC or MexAB-OprM. Class B carbapenemases (metallo-β-lactamases [MBLs]) were detected in a single isolate, although interestingly, this isolate belonged to one of the few epidemic clones documented. The MBL-encoding gene (blaVIM-2), along with the aminoglycoside resistance determinants, was transferred to strain PAO1 by electroporation, demonstrating its plasmid location. The class 1 integron harboring blaVIM-2 was characterized as well, and two interesting features were revealed: intI1 was found to be disrupted by a 1.1-kb insertion sequence, and a previously undescribed aminoglycoside acetyltransferase-encoding gene [designated aac(6′)-32] preceded blaVIM-2. AAC(6′)-32 showed 80% identity to AAC(6′)-Ib′ and the recently described AAC(6′)-31, and when aac(6′)-32 was cloned into Escherichia coli, it conferred resistance to tobramycin and reduced susceptibility to gentamicin and amikacin. Despite the currently low prevalence of epidemic clones with MDR, active surveillance is needed to detect and prevent the dissemination of these clones, particularly those producing integron- and plasmid-encoded MBLs, given their additional capacity for the intra- and interspecies spread of MDR.
PMCID: PMC2167976  PMID: 17938181
12.  Outbreaks of Multidrug-Resistant Pseudomonas aeruginosa in Community Hospitals in Japan▿  
Journal of Clinical Microbiology  2006;45(3):979-989.
We previously reported an outbreak in a neurosurgery ward of catheter-associated urinary tract infection with multidrug-resistant (MDR) Pseudomonas aeruginosa strain IMCJ2.S1, carrying the 6′-N-aminoglycoside acetyltransferase gene [aac(6′)-Iae]. For further epidemiologic studies, 214 clinical isolates of MDR P. aeruginosa showing resistance to imipenem (MIC ≥ 16 μg/ml), amikacin (MIC ≥ 64 μg/ml), and ciprofloxacin (MIC ≥ 4 μg/ml) were collected from 13 hospitals in the same prefecture in Japan. We also collected 70 clinical isolates of P. aeruginosa that were sensitive to one or more of these antibiotics and compared their characteristics with those of the MDR P. aeruginosa isolates. Of the 214 MDR P. aeruginosa isolates, 212 (99%) were serotype O11. We developed a loop-mediated isothermal amplification (LAMP) assay and a slide agglutination test for detection of the aac(6′)-Iae gene and the AAC(6′)-Iae protein, respectively. Of the 212 MDR P. aeruginosa isolates, 212 (100%) and 207 (98%) were positive in the LAMP assay and in the agglutination test, respectively. Mutations of gyrA and parC genes resulting in amino acid substitutions were detected in 213 of the 214 MDR P. aeruginosa isolates (99%). Of the 214 MDR P. aeruginosa isolates, 212 showed pulsed-field gel electrophoresis patterns with ≥70% similarity to that of IMCJ2.S1 and 83 showed a pattern identical to that of IMCJ2.S1, indicating that clonal expansion of MDR P. aeruginosa occurred in community hospitals in this area. The methods developed in this study to detect aac(6′)-Iae were rapid and effective in diagnosing infections caused by various MDR P. aeruginosa clones.
PMCID: PMC1829129  PMID: 17122009
13.  Drug Resistance of Pseudomonas aeruginosa and Enterobacter cloacae Isolated from ICU, Babol, Northern Iran 
Multidrug resistant (MDR) bacteria are spread throughout the world which causes nosocomial infections, especially in Intensive Care Unit (ICU). This study aimed to investigate the resistance pattern of Pseudomonas aeruginosa and Enterobacter cloacae isolated from patients in the ICU. During 2011-2012, 30 isolates for each P. aeruginosa and E. cloacae were collected from the patients who acquired nosocomial infection after admition to the ICU at the hospitals affiliated to Babol University of Medical Sciences, Babol, northern Iran. Antimicrobial susceptibility test was performed for five category antibiotics by microdilution method. The data were analyzed by SPSS version 20 and p<0.05 was considered statistically significant. The highest resistance rate of P. aeruginosa was seen to amikacin (53.3%) followed by ceftazidime (43.3%). Also, 16.7% of E. cloacae was resistant to ceftazidime. Among P. aeruginosa isolates,18 (60%) were MDR while no E. cloacae isolates were MDR. The significant correlation was only demonstrated between MDR P. aeruginosa and the reason of hospitalization (P=0.004). In conclusion, there was alarming amount of P. aeruginosa MDR in patients in the ICU which could lead to a hazardous outcome for the patients. Therefore, new prevention policies regarding to hospital infection should be established. Also, the periodical assessment of bacterial resistance pattern particularly in ICUs should be performed.
PMCID: PMC3927384  PMID: 24551814
Intensive care unit; nosocomial infections; P aeruginos; E cloacae
14.  The Infectiousness of Tuberculosis Patients Coinfected with HIV 
PLoS Medicine  2008;5(9):e188.
The current understanding of airborne tuberculosis (TB) transmission is based on classic 1950s studies in which guinea pigs were exposed to air from a tuberculosis ward. Recently we recreated this model in Lima, Perú, and in this paper we report the use of molecular fingerprinting to investigate patient infectiousness in the current era of HIV infection and multidrug-resistant (MDR) TB.
Methods and Findings
All air from a mechanically ventilated negative-pressure HIV-TB ward was exhausted over guinea pigs housed in an airborne transmission study facility on the roof. Animals had monthly tuberculin skin tests, and positive reactors were removed for autopsy and organ culture for M. tuberculosis. Temporal exposure patterns, drug susceptibility testing, and DNA fingerprinting of patient and animal TB strains defined infectious TB patients. Relative patient infectiousness was calculated using the Wells-Riley model of airborne infection. Over 505 study days there were 118 ward admissions of 97 HIV-positive pulmonary TB patients. Of 292 exposed guinea pigs, 144 had evidence of TB disease; a further 30 were tuberculin skin test positive only. There was marked variability in patient infectiousness; only 8.5% of 118 ward admissions by TB patients were shown by DNA fingerprinting to have caused 98% of the 125 characterised cases of secondary animal TB. 90% of TB transmission occurred from inadequately treated MDR TB patients. Three highly infectious MDR TB patients produced 226, 52, and 40 airborne infectious units (quanta) per hour.
A small number of inadequately treated MDR TB patients coinfected with HIV were responsible for almost all TB transmission, and some patients were highly infectious. This result highlights the importance of rapid TB drug-susceptibility testing to allow prompt initiation of effective treatment, and environmental control measures to reduce ongoing TB transmission in crowded health care settings. TB infection control must be prioritized in order to prevent health care facilities from disseminating the drug-resistant TB that they are attempting to treat.
Using a guinea pig detection system above an HIV-tuberculosis ward, Rod Escombe and colleagues found that most transmitted tuberculosis originated from patients with inadequately treated multidrug-resistant tuberculosis.
Editors' Summary
Every year, more than nine million people develop tuberculosis—a contagious infection usually of the lungs—and nearly two million people die from the disease. Tuberculosis is caused by Mycobacterium tuberculosis. These bacteria are spread in airborne droplets when people with the disease cough or sneeze. Most people infected with M. tuberculosis never become ill—their immune system contains the infection. However, the bacteria remain dormant within the body and can cause tuberculosis years later if host immunity declines. The symptoms of tuberculosis include a persistent cough, weight loss, and night sweats. Diagnostic tests for the disease include chest X-rays, the tuberculin skin test, and sputum cultures (in which bacteriologists try to grow M. tuberculosis from mucus brought up from the lungs by coughing). Tuberculosis can usually be cured by taking several powerful antibiotics daily for several months.
Why Was This Study Done?
Scientists performed definitive experiments on airborne tuberculosis transmission in the 1950s by exposing guinea pigs to the air from a tuberculosis ward. They found that a minority of patients actually transmit tuberculosis, that the infectiousness of transmitters varies greatly, and that effective antibiotic treatment decreases infectiousness. Since the 1950s, however, multidrug-resistant (MDR) and more recently extensively drug-resistant (XDR) strains of M. tuberculosis have become widespread. Treatment of drug-resistant tuberculosis is much more difficult than normal tuberculosis, requiring even more antibiotics, and for long periods, up to 2 years and beyond. In addition, HIV (the virus that causes AIDS) has emerged. HIV weakens the immune system so HIV-positive people are much more likely to develop active tuberculosis (and to die from the disease, which also speeds the development of HIV/AIDS) than people with a healthy immune system. Have these changes altered tuberculosis transmission between people? The answer to this question might help to optimize the control of tuberculosis infection, particularly in hospitals. In this study, the researchers investigate current patterns of tuberculosis infectiousness among HIV-positive patients by recreating the 1950s guinea pig model for tuberculosis transmission in a hospital in Lima, Perú.
What Did the Researchers Do and Find?
The researchers passed all the air from an HIV–tuberculosis ward over guinea pigs housed in an animal facility on the hospital's roof. The guinea pigs were tested monthly with tuberculin skin tests, and tissues from positive animals were examined for infection with M. tuberculosis. Sputum was also collected daily from the patients on the ward. The researchers then used the timing of patient admissions and guinea pig infections, together with the drug susceptibility patterns and DNA fingerprints of the M. tuberculosis strains isolated from the animals and the patients, to identify which patients had infected which guinea pigs. Finally, they used a mathematical equation to calculate the relative infectiousness of each patient in airborne infectious units (“quanta”) per hour. During the 505 study days, although 97 HIV-positive patients with tuberculosis were admitted to the ward, just ten patients were responsible for virtually all the characterized cases of tuberculosis among the guinea pigs. Six of these patients had MDR tuberculosis that had been suboptimally treated. The average patient infectiousness over the entire study period was 8.2 quanta per hour—six times greater than the average infectiousness recorded in the 1950s. Finally, the three most infectious patients (all of whom had suboptimally treated MDR tuberculosis) produced 226, 52, and 40 quanta per hour.
What Do These Findings Mean?
These findings show that a few inadequately treated HIV-positive patients with MDR tuberculosis caused nearly all the tuberculosis transmission to guinea pigs during this study. They also show for the first time that tuberculosis infectiousness among HIV-positive patients is very variable. The increase in the average patient infectiousness in this study compared to that seen in the 1950s hints at the possibility that HIV infection might increase tuberculosis infectiousness. However, studies that directly compare the tuberculosis infectiousness of HIV-positive and HIV-negative patients are needed to test this possibility. More importantly, this study demonstrates the potentially high infectiousness of inadequately treated MDR TB patients and their importance in ongoing TB transmission. These findings suggest that rapid, routine testing of antibiotic susceptibility should improve tuberculosis control by ensuring that patients with MDR TB are identified and treated effectively and quickly. Finally, they re-emphasize the importance of implementing environmental control measures (for example, adequate natural or mechanical ventilation of tuberculosis wards, or crowded waiting rooms or emergency departments where tuberculosis patients may be found) to prevent airborne tuberculosis transmission in health-care facilities, particularly in areas where many patients are HIV positive and/or where MDR tuberculosis is common.
Additional Information.
Please access these Web sites via the online version of this summary at
The US National Institute of Allergy and Infectious Diseases provides information on all aspects of tuberculosis, including multidrug-resistance tuberculosis, and on tuberculosis and HIV
The US Centers for Disease Control and Prevention provide several fact sheets and other information resources about all aspects of tuberculosis (in English and Spanish)
The World Health Organization's 2008 report on global tuberculosis control—surveillance, planning, financing provides a snapshot of the current state of the global tuberculosis epidemic and links to information about all aspects of tuberculosis and its control (in several languages)
HIVInsite provides detailed information about coinfection with HIV and tuberculosis
• Avert, an international AIDS charity, also provides information about the interaction between HIV and tuberculosis
Tuberculosis Infection-Control in the Era of Expanding HIV Care and Treatment is a report from the World Health Organization
PMCID: PMC2535657  PMID: 18798687
15.  Genetic diversity of clinical Pseudomonas aeruginosa isolates in a public hospital in Spain 
BMC Microbiology  2013;13:138.
Pseudomonas aeruginosa is an important nosocomial pathogen that exhibits multiple resistances to antibiotics with increasing frequency, making patient treatment more difficult. The aim of the study is to ascertain the population structure of this clinical pathogen in the Hospital Son Llàtzer, Spain.
A significant set (56) of randomly selected clinical P. aeruginosa isolates, including multidrug and non-multidrug resistant isolates, were assigned to sequence types (STs) and compared them with their antibiotic susceptibility profile classified as follows: extensively drug resistant (XDR), multidrug resistant (MDR) and non-multidrug resistant (non-MDR). The genetic diversity was assessed by applying the multilocus sequence typing (MLST) scheme developed by Curran and collaborators, and by the phylogenetic analysis of a concatenated tree. The analysis of seven loci, acsA, aroE, guaA, mutL, nuoD, ppsA and trpE, demonstrated that the prevalent STs were ST-175, ST-235 and ST-253. The majority of the XDR and MDR isolates were included in ST-175 and ST-235. ST-253 is the third in frequency and included non-MDR isolates. The 26 singleton sequence types corresponded mainly to non-MDR isolates. Twenty-two isolates corresponded to new sequence types (not previously defined) of which 12 isolates were non-MDR and 10 isolates were MDR or XDR.
The population structure of clinical P. aeruginosa present in our hospital indicates the coexistence of nonresistant and resistant isolates with the same sequence type. The multiresistant isolates studied are grouped in the prevalent sequence types found in other Spanish hospitals and at the international level, and the susceptible isolates correspond mainly to singleton sequence types.
PMCID: PMC3706262  PMID: 23773707
Pseudomonas aeruginosa; Multilocus sequence typing; Multiresistant; Clinical isolates; Population structure
16.  Carbapenem-associated multidrug-resistant Acinetobacter baumannii are sensitised by aztreonam in combination with polyamines 
Carbapenem-associated multidrug-resistant Acinetobacter baumannii (MDR-Ab) are common among clinical isolates worldwide and are a major therapeutic challenge. Previously it was shown that exogenous polyamines (spermine and spermidine) enhanced susceptibility to β-lactams but induced resistance to polymyxins in Pseudomonas aeruginosa. This study aimed to explore the possible availability of exogenous polyamines in treating carbapenem-associated MDR-Ab. The effects of polyamines on the growth rate of A. baumannii, minimal inhibitory concentrations (MICs) of antibiotics, and time–kill and checkerboard assays were determined. Roles of lipopolysaccharide (LPS) and β-lactamase activity of A. baumannii were also assessed for the polyamine effects. Growth of A. baumannii was unaffected at 4 mM spermine and 16 mM spermidine alone, but was significantly inhibited by a subinhibitory concentration of aztreonam (AZT) (8 μg/mL) and those concentrations of the polyamines. MICs to AZT alone (≥128 μg/mL) were reduced to the range 0.25–8 μg/mL in combination with polyamines in all carbapenem-associated MDR-Ab. MICs to penicillins, but not to ceftazidime and meropenem, were also significantly reduced, whilst MICs to other antibiotics, including polymyxin B, were unaffected in combination with polyamines for all tested A. baumannii. Polyamine effects on AZT were strongly synergistic with bactericidal activity and were retained at concentrations of 5 mM MgCl2 (or CaCl2) or 200 mM NaCl. Roles of LPS and β-lactamase in the polyamine effects were excluded. Overall results suggest that AZT in combination with polyamines may be useful for the treatment of carbapenem-associated MDR-Ab.
PMCID: PMC3530022  PMID: 23148986
Polyamines; β-Lactam susceptibility; Acinetobacter baumannii
17.  Prevalence of Antimicrobial-Resistant Pathogens in Canadian Hospitals: Results of the Canadian Ward Surveillance Study (CANWARD 2008) ▿  
Antimicrobial Agents and Chemotherapy  2010;54(11):4684-4693.
A total of 5,282 bacterial isolates obtained between 1 January and 31 December 31 2008, inclusive, from patients in 10 hospitals across Canada as part of the Canadian Ward Surveillance Study (CANWARD 2008) underwent susceptibility testing. The 10 most common organisms, representing 78.8% of all clinical specimens, were as follows: Escherichia coli (21.4%), methicillin-susceptible Staphylococcus aureus (MSSA; 13.9%), Streptococcus pneumoniae (10.3%), Pseudomonas aeruginosa (7.1%), Klebsiella pneumoniae (6.0%), coagulase-negative staphylococci/Staphylococcus epidermidis (5.4%), methicillin-resistant S. aureus (MRSA; 5.1%), Haemophilus influenzae (4.1%), Enterococcus spp. (3.3%), Enterobacter cloacae (2.2%). MRSA comprised 27.0% (272/1,007) of all S. aureus isolates (genotypically, 68.8% of MRSA were health care associated [HA-MRSA] and 27.6% were community associated [CA-MRSA]). Extended-spectrum β-lactamase (ESBL)-producing E. coli occurred in 4.9% of E. coli isolates. The CTX-M type was the predominant ESBL, with CTX-M-15 the most prevalent genotype. MRSA demonstrated no resistance to ceftobiprole, daptomycin, linezolid, telavancin, tigecycline, or vancomycin (0.4% intermediate intermediate resistance). E. coli demonstrated no resistance to ertapenem, meropenem, or tigecycline. Resistance rates with P. aeruginosa were as follows: colistin (polymyxin E), 0.8%; amikacin, 3.5%; cefepime, 7.2%; gentamicin, 12.3%; fluoroquinolones, 19.0 to 24.1%; meropenem, 5.6%; piperacillin-tazobactam, 8.0%. A multidrug-resistant (MDR) phenotype occurred frequently in P. aeruginosa (5.9%) but uncommonly in E. coli (1.2%) and K. pneumoniae (0.9%). In conclusion, E. coli, S. aureus (MSSA and MRSA), P. aeruginosa, S. pneumoniae, K. pneumoniae, H. influenzae, and Enterococcus spp. are the most common isolates recovered from clinical specimens in Canadian hospitals. The prevalence of MRSA was 27.0% (of which genotypically 27.6% were CA-MRSA), while ESBL-producing E. coli occurred in 4.9% of isolates. An MDR phenotype was common in P. aeruginosa.
PMCID: PMC2976152  PMID: 20805395
18.  Antimicrobial Resistance in Pseudomonas sp. Causing Infections in Trauma Patients: A 6 Year Experience from a South Asian Country 
Drug resistance to Pseudomonas sp. has spread to such a level irrespective of the type of patients, that its pattern of distribution and antibiotic resistance needs to be studied in detail, especially in trauma patients and hence the study. A 6 year study was carried out among trauma patients to see the trend and type of resistance prevalent in the apex hospital for trauma care in India among nonduplicate isolates where multidrug-resistance (MDR), cross-resistance and pan-drug resistance in Pseudomonas sp. were analyzed. Of the total 2,269 isolates obtained, the species, which was maximally isolated was Pseudomonas aeruginosa (2,224, 98%). The highest level of resistance was seen in tetracycline (2,166, 95.5%, P < 0.001) and chloramphenicol (2,160, 95.2%, P < 0.001) and least in meropenem (1,739, 76.7%, P < 0.003). Of the total, 1,692 (74.6%) isolates were MDR in which P. aeruginosa (75%) were maximum. MDR Pseudomonas is slowing increasing since the beginning of the study period. Of 1,797 imipenem-resistant P. aeruginosa isolated during the study period, 1,763 (98%) showed resistance to ciprofloxacin or levofloxacin, suggesting that cross-resistance may have developed for imipenem due to prior use of fluoroquinolones. Antibiotic resistance in Pseudomonas sp. is fast becoming a problem in trauma patients, especially in those who requires prolong hospital stay, which calls for proper antimicrobial stewardship.
PMCID: PMC4265834  PMID: 25538457
Antibiotic resistance; Cross-resistance; Infections; Multi-drug resistance; Pseudomonas spp; Trauma
19.  Structure–Function Aspects of PstS in Multi-Drug–Resistant Pseudomonas aeruginosa  
PLoS Pathogens  2008;4(2):e43.
The increasing prevalence of multi-drug–resistant (MDR) strains of Pseudomonas aeruginosa among critically ill humans is of significant concern. In the current study, we show that MDR clinical isolates of P. aeruginosa representing three distinct genotypes that display high virulence against intestinal epithelial cells, form novel appendage-like structures on their cell surfaces. These appendages contain PstS, an extracellular phosphate binding protein. Using anti-PstS antibodies, we determined that the PstS-rich appendages in MDR strains are involved in adherence to and disruption of the integrity of cultured intestinal epithelial cell monolayers. The outer surface–expressed PstS protein was also identified to be present in P. aeruginosa MPAO1, although to a lesser degree, and its role in conferring an adhesive and barrier disruptive phenotype against intestinal epithelial cells was confirmed using an isogenic ΔPstS mutant. Formation of the PstS rich appendages was induced during phosphate limitation and completely suppressed in phosphate-rich media. Injection of MDR strains directly into the intestinal tract of surgically injured mice, a known model of phosphate limitation, caused high mortality rates (60%–100%). Repletion of intestinal phosphate in this model completely prevented mortality. Finally, significantly less outer surface PstS was observed in the MPAO1 mutant ΔHxcR thus establishing a role for the alternative type II secretion system Hxc in outer surface PstS expression. Gene expression analysis performed by RT-PCR confirmed this finding and further demonstrated abundant expression of pstS analogous to pa5369, pstS analogous to pa0688/pa14–55410, and hxcX in MDR strains. Taken together, these studies provide evidence that outer surface PstS expression confers a highly virulent phenotype of MDR isolates against the intestinal epithelium that alters their adhesive and barrier disrupting properties against the intestinal epithelium.
Author Summary
The resistance of bacteria to multiple antibiotics is a major problem in critically ill patients who often become colonized by highly lethal pathogens such as Pseudomonas aeruginosa. During the course of critical illness, as many as 50% of patients' intestinal tracts become colonized with P. aeruginosa, with as many as 30% of strains being resistant to multiple antibiotics. Concomitantly, critical illness is characterized by acute depletion of phosphate, which itself has been shown to be an independent predictor of infection-related mortality. In the present study we determined that during low phosphate conditions, highly virulent multi-antibiotic–resistant strains of P. aeruginosa isolated from critically ill patients produce an abundance of the phosphate-binding protein, PstS, located on extracellular finger-like structures. These PstS rich appendages participate in the binding of P. aeruginosa to intestinal lining cells and may allow P. aeruginosa to acquire phosphate from its host while remaining at arm's length from the host immune system. This clever tactic may be one example by which successful opportunistic pathogens such as P. aeruginosa survive within complex ecological niches such as the intestinal tract and harm their hosts during the course of critical illness.
PMCID: PMC2242829  PMID: 18282104
20.  Multidrug-resistant bacterial isolates in infected wounds at Jimma University Specialized Hospital, Ethiopia 
The term ’Multidrug-resistant’ (MDR) applies to a bacterium that is simultaneously resistant to a number of antimicrobials belonging to different chemical classes. The effectiveness of currently available antmicrobial drugs is decreasing due to the increasing number of resistant strains causing infections so that available therapeutic options for such organisms are severely limited.
The aim of this study was to determine multidrug-resistance rate of bacterial isolates that caused wound infections.
A Hospital based cross-sectional study was conducted on 322 wound samples taken from consecutive patients seen at inpatient and outpatient department of Jimma University Specialized Hospital from June to December 2011. Swabs from surgical incisions, burns, abscess and traumatic wounds were collected aseptically using Levine’s technique. Bacteriological culture and examination was done following standard microbiological techniques. Multidrug-resistance test was performed by disk diffusion method against 10 classes of antimicrobials. The data was analyzed for descriptive statistics using SPSS version 16 and Microsoft Excel.
The overall MDR among gram positive and gram negative bacterial isolates were (77%) and (59.3%) respectively. About, 86.2% S.aureus and 28.6% of Coagulase negative Staphylococci became MDR. Nearly 30.1% of S.aureus was resistant to six classes of antimicrobials. The average MDR rate of Proteus, Klebsiella, and Providencia species was 74.8%, 69.6% and 75% in that order. Nearly, 30.8% of Proteus sp, 32.6% of Klebsiella sp and 61% of Citrobacter sp were resistance to 4 classes each. Surprisingly, the average MDR rate for Citrobacter sp was 100%. About (76.7%) of S.aureus was Oxacillin/Methicillin resistant while (16.4%) were Vancomycin resistant. Proteus species was the predominant isolates (27.9%) followed by P.aeruginosa and S.aureus (19.3%) and (19%) respectively.
This study indicated that, the overall rate of MDR bacterial pathogens that caused wound infection was very high and many of the isolates were also identified as resistant to three or more classes of antimicrobials. Such widespread resistance to antimicrobial classes is something serious because a few treatment options remain for patients with wound infections. Periodic monitoring of etiology and antimicrobial susceptibility in areas where there is no culture facility is essential to assists physician in selection of chemotherapy.
PMCID: PMC3724577  PMID: 23879886
Multi drug resistance; Wound infection; Jimma; Ethiopia
21.  Pseudomonas aeruginosa Population Structure Revisited 
PLoS ONE  2009;4(11):e7740.
At present there are strong indications that Pseudomonas aeruginosa exhibits an epidemic population structure; clinical isolates are indistinguishable from environmental isolates, and they do not exhibit a specific (disease) habitat selection. However, some important issues, such as the worldwide emergence of highly transmissible P. aeruginosa clones among cystic fibrosis (CF) patients and the spread and persistence of multidrug resistant (MDR) strains in hospital wards with high antibiotic pressure, remain contentious. To further investigate the population structure of P. aeruginosa, eight parameters were analyzed and combined for 328 unrelated isolates, collected over the last 125 years from 69 localities in 30 countries on five continents, from diverse clinical (human and animal) and environmental habitats. The analysed parameters were: i) O serotype, ii) Fluorescent Amplified-Fragment Length Polymorphism (FALFP) pattern, nucleotide sequences of outer membrane protein genes, iii) oprI, iv) oprL, v) oprD, vi) pyoverdine receptor gene profile (fpvA type and fpvB prevalence), and prevalence of vii) exoenzyme genes exoS and exoU and viii) group I pilin glycosyltransferase gene tfpO. These traits were combined and analysed using biological data analysis software and visualized in the form of a minimum spanning tree (MST). We revealed a network of relationships between all analyzed parameters and non-congruence between experiments. At the same time we observed several conserved clones, characterized by an almost identical data set. These observations confirm the nonclonal epidemic population structure of P. aeruginosa, a superficially clonal structure with frequent recombinations, in which occasionally highly successful epidemic clones arise. One of these clones is the renown and widespread MDR serotype O12 clone. On the other hand, we found no evidence for a widespread CF transmissible clone. All but one of the 43 analysed CF strains belonged to a ubiquitous P. aeruginosa “core lineage” and typically exhibited the exoS+/exoU− genotype and group B oprL and oprD alleles. This is to our knowledge the first report of an MST analysis conducted on a polyphasic data set.
PMCID: PMC2777410  PMID: 19936230
22.  Activity of a New Antipseudomonal Cephalosporin, CXA-101 (FR264205), against Carbapenem-Resistant and Multidrug-Resistant Pseudomonas aeruginosa Clinical Strains ▿  
The activity of the new cephalosporin CXA-101 (CXA), previously designated FR264205, was evaluated against a collection of 236 carbapenem-resistant P. aeruginosa isolates, including 165 different clonal types, from a Spanish multicenter (127-hospital) study. The MICs of CXA were compared to the susceptibility results for antipseudomonal penicillins, cephalosporins, carbapenems, aminoglycosides, and fluoroquinolones. The MIC of CXA in combination with tazobactam (4 and 8 μg/ml) was determined for strains with high CXA MICs. The presence of acquired β-lactamases was investigated by isoelectric focusing and PCR amplification followed by sequencing. Additional β-lactamase genes were identified by cloning and sequencing. The CXA MIC50/MIC90 for the complete collection of carbapenem-resistant P. aeruginosa isolates was 1/4 μg/ml, with 95.3% of the isolates showing an MIC of ≤8 μg/ml. Cross-resistance with any of the antibiotics tested was not observed; the MIC50/MIC90 of CXA-101 was still 1/4 when multidrug-resistant (MDR) strains (42% of all tested isolates) or AmpC-hyperproducing clones (53%) were analyzed. Almost all (10/11) of the strains showing a CXA MIC of >8 μg/ml produced a horizontally acquired β-lactamase, including the metallo-β-lactamase (MBL) VIM-2 (one strain), the extended-spectrum β-lactamase (ESBL) PER-1 (one strain), several extended-spectrum OXA enzymes (OXA-101 [one strain], OXA-17 [two strains], and a newly described OXA-2 derivative [W159R] designated OXA-144 [four strains]), and a new BEL variant (BEL-3) ESBL (one strain), as identified by cloning and sequencing. Synergy with tazobactam in these 11 strains was limited, although 8 μg/ml reduced the mean CXA MIC by 2-fold. CXA is highly active against carbapenem-resistant P. aeruginosa isolates, including MDR strains. Resistance was restricted to still-uncommon strains producing an acquired MBL or ESBL.
PMCID: PMC2812131  PMID: 19933793
23.  Microbiology, resistance patterns, and risk factors of mortality in ventilator-associated bacterial pneumonia in a Northern Thai tertiary-care university based general surgical intensive care unit 
Ventilator-associated pneumonia (VAP) occurrence, causative pathogens, and resistance patterns in surgical intensive care units (SICU) are different between Western and developing Asian countries. In Thailand, resistant organisms have progressively increased in the last decade. However, the evidence describing causes of VAP and its outcomes, especially secondary to resistant pathogens, in Asian developing countries’ SICUs is very limited. Therefore, the objective of this study was to describe the incidence, pathogen characteristics, and risk factors that impact mortality and patient survival following VAP in a tertiary Northern Thai SICU.
Between 2008 and 2012, VAP occurred in a total of 150 patients in Chiang Mai University’s general SICUs (6.3±2.8 cases per 1,000 mechanical ventilator days). The following clinical data were collected from 46 patients who died and 104 patients who survived: microbiologic results, susceptible patterns, and survival status at hospital discharge. Antimicrobial susceptibility patterns were classified as susceptible, multidrug resistant (MDR), extensively drug resistant (XDR), and pan-drug resistant (PDR). The hazard ratio (HR) was calculated for risk factor analysis.
Regarding the microbiology, gram negative organisms were the major pathogens (n=142, 94.7%). The first three most common organisms were Acinetobacter baumannii (38.7% of all organisms, mortality 41.4%), Klebsiella pneumoniae (17.3%, mortality 30.8%), and Pseudomonas aeruginosa (16.7%, mortality 16%) respectively. The most common gram positive organism was Staphylococcus aureus (4.0%, mortality 50%). The median day of VAP occurrence were significantly different between the three groups (P<0.01): susceptible (day 4), MDR (day 5), and XDR (day 6.5). Only half of all VAP cases were caused by susceptible organisms. Antibiotic resistance was demonstrated by 49.3% of the gram negative organisms and 62.5% of the gram positive organisms. Extensive drug resistance was evident only in Acinetobacter baumannii (30.6%) and Pseudomonas aeruginosa (1.3%). No pan-drug resistance was found during surveillance. The significant HR risk factors were age (P=0.03), resistant organisms (P=0.04), XDR (P=0.02), and acute physiology and chronic health evaluation II score (<0.01). Acinetobacter baumannii (P=0.06) and intubation due to severe sepsis (P=0.08) demonstrated a trend toward a significant increase in the HR. On the other hand, there were significantly decreased HRs in trauma patients (P=0.01). Initial administration of appropriate antibiotic therapy had a tendency toward a significant decrease in the HR (P=0.08).
Gram negative organisms were the primary cause of bacterial VAP in Chiang Mai University’s general SICU. Resistant strains were present in half of all VAP cases and were associated with the day of VAP onset. Regarding risk factors, age, acute physiology, chronic health evaluation II score, resistant organisms (especially XDR), and being a non-trauma patient increased the risk of mortality.
PMCID: PMC4140702  PMID: 25152627
surgical intensive care unit; ventilator-associated pneumonia; device-related incidence rate; drug resistant organism; Acinetobacter baumannii
24.  Epidemiology of carbapenem non-susceptible Pseudomonas aeruginosa isolates in Eastern Algeria 
Carbapenem resistance among Pseudomonas aeruginosa has become a serious life-threatening problem due to the limited therapeutic options. In this study, we investigated the prevalence and the molecular epidemiology of carbapenem resistant Pseudomonas aeruginosa (CRPA) isolated from three hospitals in Annaba city, Algeria.
During the study period (January, 2012 to December, 2013), all patients infected by P. aeruginosa were considered as the potential study population. Antibiotic susceptibility testing was performed as recommended by the CLSI. Screening of carbapenemase producer isolates was performed by using imipenem-EDTA double-disk synergy test and modified Hodge test. CRPA isolates were tested for the presence of genes encoding β-lactamases, plasmid mediated quinolone resistance, aminoglycoside resistance and class 1 integrons were investigated by PCR and sequencing. The clonal relatedness among CRPA isolates was analyzed by pulsed-field gel electrophoresis method. The clinical data were collected to identify risk factors for CRPA carriage of P. aeruginosa infection.
The overall prevalence of CRPA was 18.75 %. The risk factors for carrying CRPA were the length of hospital stay (p = 0.04), co-infections with Staphylococcus aureus (p = 0.01), and the use of urinary catheter (p = 0.03). The in-hospital mortality rate among case patients was 13.33 % compared with 1.53 % for control patients (p = 0.09). All CRPA isolates were multidrug resistance and the most effective antibiotic against CRPA isolates was amikacin and colistin. PFGE revealed an epidemic clonal dissemination of CRPA isolates. None of CRPA isolated were found to be carbapenemase-producers. The blaPSE-1 and aac(3)-II gene was detected in two and five strains respectively. The class1 integrons were detected in 2 isolates with the presence of aadA7 gene cassette in these integrons.
The endemic clonal dissemination and multi-drug resistance of CRPA isolates in our institution is highly alarming. Strict measure will be required to control the further spread of these pathogens in hospital setting.
PMCID: PMC4465145  PMID: 26075066
Pseudomonas aeruginosa; Prevalence; Risk factors; Carbapenem resistance
25.  Molecular Epidemiology of Pseudomonas aeruginosa Colonization in a Burn Unit: Persistence of a Multidrug-Resistant Clone and a Silver Sulfadiazine-Resistant Clone 
Journal of Clinical Microbiology  2003;41(3):1192-1202.
To study the epidemiology of Pseudomonas aeruginosa colonization in a 32-bed burn wound center (BWC), 321 clinical and 45 environmental P. aeruginosa isolates were collected by prospective surveillance culture over a 1-year period and analyzed by serotyping, drug susceptibility testing, and amplified fragment length polymorphism (AFLP) analysis. Among 441 patients treated at the center, 70 (16%) were colonized with P. aeruginosa, including 12 (17%) patients who were colonized on admission and 58 (83%) patients who acquired the organism during their stay. Of the 48 distinct AFLP genotypes found, 21 were found exclusively in the environment, 15 were isolated from individual patients only, and 12 were responsible for the colonization of 57 patients, of which 2 were also isolated from the environment, but secondary to patient carriage. Polyclonal P. aeruginosa colonization with strains of two to four genotypes, often with different antibiotic susceptibility patterns, was observed in 19 patients (27%). Two predominant genotypes were responsible for recurrent outbreaks and the colonization of 42 patients (60% of all colonized patients). The strain with one of those genotypes appeared to be endemic to the BWC and developed multidrug resistance (MDR) at the end of the study period, whereas the strain with the other genotype was antibiotic susceptible but resistant to silver sulfadiazine (SSDr). The MDR strain was found at a higher frequency in sputum samples than the SSDr strain, which showed a higher prevalence in burn wound samples, suggesting that anatomic habitat selection was associated with adaptive resistance to antimicrobial drugs. Repeated and thorough surveys of the hospital environment failed to detect a primary reservoir for any of those genotypes. Cross-acquisition, resulting from insufficient compliance with infection control measures, was the major route of colonization in our BWC. In addition to the AFLP pattern and serotype, analysis of the nucleotide sequences of three (lipo)protein genes (oprI, oprL, and oprD) and the pyoverdine type revealed that all predominant strains except the SSDr strain belonged to recently identified clonal complexes. These successful clones are widespread in nature and therefore predominate in the patient population, in whom variants accumulate drug resistance mechanisms that allow their transmission and persistence in the BWC.
PMCID: PMC150314  PMID: 12624051

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