Objective

To describe a Clostridium difficile infection (CDI) pseudo-outbreak caused by a faulty toxin assay lot, and to determine the effect of sensitivity, specificity, and repeat testing for C. difficile on CDI burden, positive predictive value (PPV), and false positive results.

Design

Outbreak investigation and criterion standard

Patients

Patients hospitalized at a tertiary-care hospital who had at least one toxin assay test for C. difficile from July 1, 2004 through June 30, 2006.

Methods

Run-control chart methodology and chi-square tests were used to compare CDI rates and proportion of positive tests before, during, and after the pseudo-outbreak. The impact of repeat testing was evaluated using three hypothetical models with a sample of 10,000 patients and various assay sensitivity and specificity estimates.

Results

In November of 2005, the hospital CDI rate increased from 1.5/1000 patient-days to 2.6/1000 patient-days (p<0.01) and the proportion of positive tests increased from 13.6% to 22.1% (p<0.01). Investigation revealed a pseudo-outbreak caused by a faulty toxin assay lot. A decrease of only 1.2% in the specificity of the toxin assay would result in a 32% increased in perceived CDI incidence at this institution. Using the manufacturer's specificity and sensitivity and this institution's testing practices, the PPV of the test decreased from 80.6% in a first test to 4.1% in patients who received three tests.

Conclusion

Specificity is as important as sensitivity when testing for CDI. False positive CDI cases can drain hospital resources and adversely affect patients. Repeat testing for C. difficile should be performed with caution.

Objectives

Compare Clostridium difficile infection (CDI) rates using a traditional definition [i.e. diagnosed > 48 hours after admission, healthcare-onset CDI (HO/CDI)] versus expanded definitions, including both HO/CDI cases and community-onset CDI cases diagnosed ≤ 48 hours from admission who were hospitalized in the previous 30 or 60 days [healthcare facility-associated (HCFA)-30 and HCFA-60]. Determine if differences exist between patients with CDI onset in the community versus healthcare setting.

Design

Prospective cohort

Setting

Tertiary acute-care facility.

Patients

Medicine patients diagnosed with CDI from 1/1/04 through 12/31/05.

Methods

CDI cases were classified as HO/CDI, HCFA-30, and/or HCFA-60. Patient demographics and medication exposures were obtained. The CDI incidence per the definitions, CDI rate variability, patient demographics, and medication exposures were compared.

Results

The HO/CDI rate (1.6 cases/1000 patient days) was significantly lower than the HCFA-30 (2.4) and the HCFA-60 (2.6) rates (p<0.01, both). There was good correlation between the HO/CDI rate and both the HCFA-30 and HCFA-60 rates (correlation=0.69 and 0.70, p<0.01 both). There were no months where the CDI rate was > 3 SD from the mean. Patients with community-onset CDI were less likely to have received a fourth-generation cephalosporin (p=0.02) or IV vancomycin (p=0.01) while hospitalized.

Conclusions

Expanded definitions identify more patients with CDI. There is good correlation between traditional and expanded CDI definitions; therefore it is unclear if expanded surveillance is necessary to identify an abnormal change in CDI rates. Cases that met the expanded definitions were less like to have fourth-generation cephalosporin and vancomycin exposure.

We describe the prevalence of and risk factors for colonization with extended-spectrum β-lactamase-producing Enterobacteriaceae (ESBL-EB) in the long-term care facility (LTCF) setting. Colonization prevalence differed significantly across the 3 LTCFs evaluated in the study, with recent use of levofloxacin and fecal incontinence demonstrating borderline significant associations with ESBL-EB colonization.

The study aimed to evaluate epidemiology of nosocomial pathogens and their resistance patterns at four major tertiary care centers in Tbilisi, Georgia. Out of 3452 samples included in the study 1607 positive culture results were documented (46.6%). Study showed considerable burden of nosocomial infections on Georgian health care system.

OBJECTIVE

In late 2006, our hospital implemented use of the QuantiFERON-TB Gold (QFT-G) assay, a whole-blood interferon-γ release assay, for detection of tuberculosis infection. All newly hired healthcare workers (HCWs) with positive Mantoux tuberculin skin test (TST) results were routinely tested with the QFT-G assay, to take advantage of its higher specificity. We then undertook a quality assurance review to evaluate the QFT-G test results in HCWs with multiple risk factors for latent tuberculosis infection (LTBI).

METHODS

The clinical records for TST-positive HCWs tested with the QFT-G assay were reviewed. HCWs with 2 or more risk factors commonly associated with LTBI were classified as “increased risk” (IR). IR HCWs who had negative QFT-G test results underwent repeat QFT-G testing and were offered testing with a different interferon-γ release assay (T-SPOT.TB) and with extended T cell stimulation assays.

RESULTS

Of 143 TST-positive HCWs tested with the QFT-G assay, 26 (18%) had positive results, 115 (81%) had negative results, and 2 (1%) had indeterminate results. Of 82 IR HCWs, 23 (28%) had positive QFT-G test results, and 57 (70%) had negative results. Of the 57 IR HCWs with negative results, 43 underwent repeat QFT-G testing: 41 had negative results again, and 2 had positive results. These 43 HCWs were also offered additional testing with the T-SPOT.TB diagnostic, and 36 consented: 31/36 tested negative, and 5/36 tested positive. Extended assays using the antigens ESAT-6 and CFP-10 confirmed the positive results detected by the overnight assays and yielded positive results for an additional 7/36 (19%) of individuals; strikingly, all 36 HCWs had strongly positive test results with assays using purified protein derivative.

CONCLUSIONS

The extreme discordance between the results of our clinical diagnostic algorithm and the results of QFT-G testing raises concern about the sensitivity of the QFT-G assay for detection of LTBI in our HCWs. Results of extended stimulation assays suggest that many of our IR HCWs have indeed been sensitized to Mycobacterium tuberculosis. It is possible that the QFT-G assay identifies those at higher reactivation risk rather than all previously infected, but, in the absence of long-term follow-up data, we should interpret negative QFT-G results with some caution.

To evaluate the utility of the QuantiFERON-TB Gold assay for monitoring latent tuberculosis treatment efficacy, the assay was performed serially for healthcare workers receiving isoniazid therapy. After 9 months of isoniazid therapy, all of these healthcare workers remained QuantiFERON-TB Gold positive, and cellular proliferation assays revealed persistently strong purified protein derivative responses. These results do not support the use of the QuantiFERON-TB Gold assay to monitor therapy.

We prospectively determined what proportion of nosocomial E. coli bacteriurias are associated with urinary catheters. Only 46% (95% CI 37–56%) of nosocomial E. coli bacteriurias were catheter-associated. Compared to bacteriuric patients with catheters, non-catheterized patients were less likely to be male and have renal insufficiency or a recent urogenital procedure.

OBJECTIVE

Mandatory active surveillance culturing of all patients admitted to Veterans Affairs (VA) hospitals carries substantial economic costs. Clinical prediction rules have been used elsewhere to identify patients at high risk of colonization with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE). We aimed to derive and evaluate the clinical efficacy of prediction rules for MRSA and VRE colonization in a VA hospital.

DESIGN AND SETTING

Prospective cohort of adult inpatients admitted to the medical and surgical wards of a 119-bed tertiary care VA hospital.

METHODS

Within 48 hours after admission, patients gave consent, completed a 44-item risk factor questionnaire, and provided nasal culture samples for MRSA testing. A subset provided perirectal culture samples for VRE testing.

RESULTS

Of 598 patients enrolled from August 30, 2007, through October 30, 2009, 585 provided nares samples and 239 provided perirectal samples. The prevalence of MRSA was 10.4% (61 of 585) (15.0% in patients with and 5.6% in patients without electronic medical record (EMR)–documented antibiotic use during the past year; P < .01). The prevalence of VRE was 6.3% (15 of 239) (11.3% in patients with and 0.9% in patients without EMR-documented antibiotic use; P < .01). The use of EMR-documented antibiotic use during the past year as the predictive rule for screening identified 242.8 (84%) of 290.6 subsequent days of exposure to MRSA and 60.0 (98%) of 61.0 subsequent days of exposure to VRE, respectively. EMR documentation of antibiotic use during the past year identified 301 (51%) of 585 patients as high-risk patients for whom additional testing with active surveillance culturing would be appropriate.

CONCLUSIONS

EMR documentation of antibiotic use during the year prior to admission identifies most MRSA and nearly all VRE transmission risk with surveillance culture sampling of only 51% of patients. This approach has substantial cost savings compared with the practice of universal active surveillance.

OBJECTIVE

To investigate the relationship between contact precautions and delirium among inpatients, adjusting for other factors.

DESIGN

Retrospective cohort study.

SETTING

A 662-bed tertiary care center.

PATIENTS

All nonpyschiatric adult patients admitted to a tertiary care center from 2007 through 2009.

METHODS

Generalized estimating equations were used to estimate the association between contact precautions and delirium in a retrospective cohort of 2 years of admissions to a tertiary care center.

RESULTS

During the 2-year period, 60,151 admissions occurred in 45,266 unique nonpsychiatric patients. After adjusting for comorbid conditions, age, sex, intensive care unit status, and length of hospitalization, contact precautions were significantly associated with delirium (as defined by International Classification of Diseases, Ninth Revision), medication, or restraint exposure (adjusted odds ratio [OR], 1.40 [95% confidence interval {CI}, 1.24–1.51]). The association between contact precautions and delirium was seen only in patients who were newly placed under contact precautions during the course of their stay (adjusted OR, 1.75 [95% CI, 1.60–1.92]; P < .01) and was not seen in patients who were already under contact precautions at admission (adjusted OR, 0.97 [95% CI, 0.86–1.09]; P=.60).

CONCLUSIONS

Although delirium was more common in patients who were newly placed under contact precautions during the course of their hospital admission, delirium was not associated with contact precautions started at hospital admission. Patients newly placed under contact precautions after admission but during hospitalization appear to be at a higher risk and may benefit from proven delirium-prevention strategies.

Background

Despite a paucity of evidence, decolonization measures are prescribed for outpatients with recurrent Staphylococcus aureus skin and soft tissue infections (SSTI).

Objective

Compare the effectiveness of four regimens for eradicating S. aureus carriage.

Design

Open-label, randomized controlled trial. Colonization status and recurrent SSTI were ascertained at one and four months.

Setting

Barnes-Jewish and St. Louis Children’s Hospitals, St. Louis, Missouri, 2007–2009.

Participants

Three hundred patients with community-onset SSTI and S. aureus colonization in the nares, axilla, or inguinal folds.

Interventions

Participants were randomized to receive no therapeutic intervention (controls) or perform one of three 5-day regimens: 2% mupirocin ointment applied to the nares twice daily, intranasal mupirocin plus daily 4% chlorhexidine body washes, or intranasal mupirocin plus daily dilute bleach water baths.

Results

Among 244 participants with one-month colonization data, modified intention-to-treat analysis revealed S. aureus eradication in 38% of participants in the education only (control) group; 56% in the mupirocin group (p=0.03 vs. controls); 55% in the mupirocin/chlorhexidine group (p=0.05); and 63% in the mupirocin/bleach group (p=0.006). Of 229 participants with four-month colonization data, eradication rates were 48% in controls; 56% for mupirocin only (p=0.40 vs. controls); 54% for mupirocin/chlorhexidine (p=0.51); and 71% for mupirocin/bleach (p=0.02). At one and four months, respectively, recurrent SSTI was reported by 20% and 36% of participants.

Conclusions

An inexpensive regimen of dilute bleach baths, intranasal mupirocin, and hygiene education effectively eradicated S. aureus over four months. High rates of recurrent SSTI suggest factors other than endogenous colonization as important determinants of infection.

We reviewed the medical records of all the patients who died in our hospital during the period from 2004 through 2008 to determine the contribution of healthcare-associated infections to mortality. Of the 179 unexpected in-hospital deaths during that period, 55 (31%) were related to 69 healthcare-associated infections. The most common healthcare-associated infection was central line—associated bloodstream infection, and the most common organisms identified were members of the Enterobacteriaceae family. Overall, 45% of bacterial isolates were multidrug resistant.

DESIGN

We conducted a retrospective cohort study to examine the role played by length of hospital stay in the risk of healthcare-associated bloodstream infection (BSI), independent of demographic and clinical risk factors for BSI.

PATIENTS

We employed data from 113,893 admissions from inpatients discharged between 2006 and 2008.

SETTING

Large tertiary healthcare center in New York City.

METHODS

We estimated the crude and adjusted hazard of BSI by conducting logistic regression using a person-day data structure. The covariates included in the fully adjusted model included age, sex, Charlson score of comorbidity, renal failure, and malignancy as static variables and central venous catheterization, mechanical ventilation, and intensive care unit stay as time-varying variables.

RESULTS

In the crude model, we observed a nonlinear increasing hazard of BSI with increasing hospital stay. This trend was reduced to a constant hazard when fully adjusted for demographic and clinical risk factors for BSI.

CONCLUSION

The association between longer length of hospital stay and increased risk of infection can largely be explained by the increased duration of stay among those who have underlying morbidity and require invasive procedures. We should take caution in attributing the association between length of stay and BSI to a direct negative impact of the healthcare environment.

OBJECTIVE

The purpose of this study was to describe patterns of infection or colonization with antibiotic-resistant gram-negative bacilli (GNB) in hospitalized children utilizing an electronic health record.

SETTING

Tertiary care facility.

PARTICIPANTS

Pediatric patients 18 years of age or younger hospitalized from January 1, 2006, to December 31, 2008.

METHODS

Children were identified who had (1) at least 1 positive culture for a multidrug-resistant (MDR) GNB, defined as a GNB with resistance to 3 or more antibiotic classes; or (2) additive drug resistance, defined as isolation of more than 1 GNB that collectively as a group demonstrated resistance to 3 or more antibiotic classes over the study period. Differences in clinical characteristics between the 2 groups were ascertained, including history of admissions and transfers, comorbid conditions, receipt of procedures, and antibiotic exposure.

RESULTS

Of 56,235 pediatric patients, 46 children were infected or colonized with an MDR GNB, of which 16 were resistant to 3 classes and 30 were resistant to 4 classes. Another 39 patients had positive cultures for GNB that exhibited additive drug resistance. Patients with additive drug resistance were more likely than patients with MDR GNB to have had previous admissions to a long-term facility (8 vs 2; P = .04) and had more mean admissions (7 vs 3; P < .01) and more mean antibiotic-days (P < .01 to P = .02). Six patients with additive drug resistance later had a positive culture with an MDR GNB.

CONCLUSIONS

An electronic health record can be used to track antibiotic class resistance in GNB isolated from hospitalized children over multiple cultures and hospitalizations.

Little is known about the epidemiology of nosocomial urinary tract-related bloodstream infection. In a case series from an academic medical center, Enterococcus sp. (28.7%) and Candida sp. (19.6%) were the predominant microorganisms isolated, suggesting a potential shift from previously observed Gram-negative microorganisms. A case-fatality rate of 32.8% highlights the severity of this condition.

Data from a case-control study were used to derive and internally validate a prediction rule for identifying fluoroquinolone resistance in healthcare-acquired gram-negative urinary tract infection. This prediction rule has an excellent sensitivity and specificity (C-statistic, 0.816). External validation is necessary before implementing this rule to optimize empirical antibiotic use in clinical practice.

BACKGROUND AND OBJECTIVE

Patients undergoing orthopedic surgery are susceptible to methicillin-resistant Staphylococcus aureus (MRSA) infections, which can result in increased morbidity, hospital lengths of stay, and medical costs. We sought to estimate the economic value of routine preoperative MRSA screening and decolonization of orthopedic surgery patients.

METHODS

A stochastic decision-analytic computer simulation model was used to evaluate the economic value of implementing this strategy (compared with no preoperative screening or decolonization) among orthopedic surgery patients from both the third-party payer and hospital perspectives. Sensitivity analyses explored the effects of varying MRSA colonization prevalence, the cost of screening and decolonization, and the probability of decolonization success.

RESULTS

Preoperative MRSA screening and decolonization was strongly cost-effective (incremental cost-effectiveness ratio less than $6,000 per quality-adjusted life year) from the third-party payer perspective even when MRSA prevalence was as low as 1%, decolonization success was as low as 25%, and decolonization costs were as high as $300 per patient. In most scenarios this strategy was economically dominant (ie, less costly and more effective than no screening). From the hospital perspective, preoperative MRSA screening and decolonization was the economically dominant strategy for all scenarios explored.

CONCLUSIONS

Routine preoperative screening and decolonization of orthopedic surgery patients may under many circumstances save hospitals and third-party payers money while providing health benefits.

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) can cause severe infection in patients who are undergoing vascular surgical operations. Testing all vascular surgery patients preoperatively for MRSA and attempting to decolonize those who have positive results may be a strategy to prevent MRSA infection. The economic value of such a strategy has not yet been determined.

METHODS

We developed a decision-analytic computer simulation model to determine the economic value of using such a strategy before all vascular surgical procedures from the societal and third-party payer perspectives at different MRSA prevalence and decolonization success rates.

RESULTS

The model showed preoperative MRSA testing to be cost-effective (incremental cost-effectiveness ratio, <$50,000 per quality-adjusted life year) when the MRSA prevalence is ≥0.01 and the decolonization success rate is ≥0.25. In fact, this strategy was dominant (ie, less costly and more effective) at the following thresholds: MRSA prevalence ≥0.01 and decolonization success rate ≥0.5, and MRSA prevalence ≥0.025 and decolonization success rate ≥0.25.

CONCLUSION

Testing and decolonizing patients for MRSA before vascular surgery may be a cost-effective strategy over a wide range of MRSA prevalence and decolonization success rates.

Background

Since hospitals in a region often share patients, an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) infection in one hospital could affect other hospitals.

Methods

Using extensive data collected from Orange County (OC), California, we developed a detailed agent-based model to represent patient movement among all OC hospitals. Experiments simulated MRSA outbreaks in various wards, institutions, and regions. Sensitivity analysis varied lengths of stay, intraward transmission coefficients (β), MRSA loss rate, probability of patient transfer or readmission, and time to readmission.

Results

Each simulated outbreak eventually affected all of the hospitals in the network, with effects depending on the outbreak size and location. Increasing MRSA prevalence at a single hospital (from 5% to 15%) resulted in a 2.9% average increase in relative prevalence at all other hospitals (ranging from no effect to 46.4%). Single-hospital intensive care unit outbreaks (modeled increase from 5% to 15%) caused a 1.4% average relative increase in all other OC hospitals (ranging from no effect to 12.7%).

Conclusion

MRSA outbreaks may rarely be confined to a single hospital but instead may affect all of the hospitals in a region. This suggests that prevention and control strategies and policies should account for the interconnectedness of health care facilities.

Background

Coagulase-negative staphylococci (CoNS) are the most commonly isolated pathogens in the neonatal intensive care unit (NICU). CoNS infections are associated with increased morbidity including neurodevelopmental impairment.

Objective

Describe the epidemiology of CoNS infections in the NICU. Determine mortality among infants with definite, probable, or possible CoNS infections.

Methods

We performed a retrospective cohort study of all blood, urine, and cerebrospinal fluid cultures from infants <121 postnatal days.

Setting

248 NICUs managed by the Pediatrix Medical Group from 1997 to 2009.

Results

We identified 16,629 infants with 17,624 episodes of CoNS infection: 1734 (10%) definite, 3093 (17%) probable, and 12,797 (73%) possible infections. Infants with lower gestational age and birth weight had a higher incidence of CoNS infection. Controlling for gestational age, birth weight, and 5-minute Apgar score, infants with definite, probable, or possible CoNS infection had lower mortality—OR=0.74 (95% confidence interval; 0.61, 0.89), OR= 0.68 (0.59, 0.79), and OR=0.69 (0.63, 0.76)—compared to infants with negative cultures (P<0.001). No significant difference in overall mortality was found in infants with definite CoNS infection compared to those with probable or possible CoNS infection—OR=0.93 (0.75, 1.16) and OR=0.85 (0.70, 1.03), respectively.

Conclusions

CoNS infection was strongly related to lower gestational age and birth weight. Infants with clinical sepsis and culture-positive CoNS infection had lower mortality rates than infants with clinical sepsis and negative blood culture results. No difference in mortality between infants diagnosed with definite, probable, or possible CoNS infection was observed.

Sales for a drug may be correlated with the prevalence of a condition treated by the drug. We found that state data revealed a strong spatial association and national data a strong temporal association between Clostridium difficile and oral vancomycin prescription sales, suggesting a new “signal” for detecting disease activity.

We show that respiratory fluoroquinolone use is extremely seasonal and that fluoroquinolone use is strongly associated with influenza. In our time series model, instantaneous influenza activity was a significant predictor of use (P < .0001). Also, we estimated that reducing influenza activity by 20% would reduce prescriptions by 8%.

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) transmission and infections are a continuing problem in hospitals. Although some have recommended universal surveillance for MRSA at hospital admission to identify and to isolate MRSA-colonized patients, there is a need for formal economic studies to determine the cost-effectiveness of such a strategy.

METHODS

We developed a stochastic computer simulation model to determine the potential economic impact of performing MRSA surveillance (ie, single culture of an anterior nares specimen) for all hospital admissions at different MRSA prevalences and basic reproductive rate thresholds from the societal and third party–payor perspectives. Patients with positive surveillance culture results were placed under isolation precautions to prevent transmission by way of respiratory droplets. MRSA-colonized patients who were not isolated could transmit MRSA to other hospital patients.

RESULTS

The performance of universal MRSA surveillance was cost-effective (defined as an incremental cost-effectiveness ratio of less than $50,000 per quality-adjusted life-year) when the basic reproductive rate was 0.25 or greater and the prevalence was 1% or greater. In fact, surveillance was the dominant strategy when the basic reproductive rate was 1.5 or greater and the prevalence was 15% or greater, the basic reproductive rate was 2.0 or greater and the prevalence was 10% or greater, and the basic reproductive rate was 2.5 or greater and the prevalence was 5% or greater.

CONCLUSIONS

Universal MRSA surveillance of adults at hospital admission appears to be cost-effective at a wide range of prevalence and basic reproductive rate values. Individual hospitals and healthcare systems could compare their prevailing conditions (eg, the prevalence of MRSA colonization and MRSA transmission dynamics) with the benchmarks in our model to help determine their optimal local strategies.