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1.  Trends in Staphylococcus aureus bacteraemia and impacts of infection control practices including universal MRSA admission screening in a hospital in Scotland, 2006–2010: retrospective cohort study and time-series intervention analysis 
BMJ Open  2012;2(3):e000797.
To describe secular trends in Staphylococcus aureus bacteraemia (SAB) and to assess the impacts of infection control practices, including universal methicillin-resistant Staphylococcus aureus (MRSA) admission screening on associated clinical burdens.
Retrospective cohort study and multivariate time-series analysis linking microbiology, patient management and health intelligence databases.
Teaching hospital in North East Scotland.
All patients admitted to Aberdeen Royal Infirmary between 1 January 2006 and 31 December 2010: n=420 452 admissions and 1 430 052 acute occupied bed days (AOBDs).
Universal admission screening programme for MRSA (August 2008) incorporating isolation and decolonisation.
Primary and secondary measures
Hospital-wide prevalence density, hospital-associated incidence density and death within 30 days of MRSA or methicillin-sensitive Staphylococcus aureus (MSSA) bacteraemia.
Between 2006 and 2010, prevalence density of all SAB declined by 41%, from 0.73 to 0.50 cases/1000 AOBDs (p=0.002 for trend), and 30-day mortality from 26% to 14% (p=0.013). Significant reductions were observed in MRSA bacteraemia only. Overnight admissions screened for MRSA rose from 43% during selective screening to >90% within 4 months of universal screening. In multivariate time-series analysis (R2 0.45 to 0.68), universal screening was associated with a 19% reduction in prevalence density of MRSA bacteraemia (−0.035, 95% CI −0.049 to −0.021/1000 AOBDs; p<0.001), a 29% fall in hospital-associated incidence density (−0.029, 95% CI −0.035 to −0.023/1000 AOBDs; p<0.001) and a 46% reduction in 30-day mortality (−15.6, 95% CI −24.1% to −7.1%; p<0.001). Positive associations with fluoroquinolone and cephalosporin use suggested that antibiotic stewardship reduced prevalence density of MRSA bacteraemia by 0.027 (95% CI 0.015 to 0.039)/1000 AOBDs. Rates of MSSA bacteraemia were not significantly affected by screening or antibiotic use.
Declining clinical burdens from SAB were attributable to reductions in MRSA infections. Universal admission screening and antibiotic stewardship were associated with decreases in MRSA bacteraemia and associated early mortality. Control of MSSA bacteraemia remains a priority.
Article summary
Article focus
This study describes the changing epidemiology of MRSA and MSSA bacteraemia in a large inpatient population from Scotland over a 5-year period.
Second, it evaluates the impact of universal MRSA admission screening, and other infection control practices, on hospital-wide rates of MRSA bacteraemia.
Key messages
Recent declines in clinical burdens from SAB in North East Scotland were attributable to a reduction in invasive MRSA infections.
Compared with a strategy of targeted screening in high-risk environments, universal admission screening may significantly reduce rates of MRSA bacteraemia and associated early mortality alongside improvements in antibiotic stewardship and infection control.
Strategies to reduce clinical burdens from MSSA bacteraemia are required if progress towards national targets for all SAB is to be sustained.
Strengths and limitations of this study
Without a contemporary control, this study did not prove causality but a temporal association between universal admission screening and rates of MRSA bacteraemia.
ARIMA modelling accounted for the non-independence of data and stochastic elements in time series of infections, and the dynamic effects of changes in other aspects of care.
Findings may be limited to large public hospitals with intensive care units and endemic MRSA but low rates of MRSA infection.
PMCID: PMC3378947  PMID: 22685226
2.  Treatment Duration for Uncomplicated Staphylococcus aureus Bacteremia To Prevent Relapse: Analysis of a Prospective Observational Cohort Study 
Practice guidelines recommend at least 14 days of antibiotic therapy for uncomplicated Staphylococcus aureus bacteremia (SAB). However, these recommendations have not been formally evaluated in clinical studies. To evaluate the duration of therapy for uncomplicated SAB, we analyzed data from our prospective cohort of patients with SAB. A prospective observational cohort study was performed in patients with SAB at a tertiary-care hospital in Korea between August 2008 and September 2010. All adult patients with SAB were prospectively enrolled and observed over a 12-week period. Uncomplicated SAB was defined as follows: negative results of follow-up blood cultures at 2 to 4 days, defervescence within 72 h of therapy, no evidence of metastatic infection, and catheter-related bloodstream infection or primary bacteremia without evidence of endocarditis on echocardiography. Of 483 patients with SAB, 111 met the study criteria for uncomplicated SAB. Fifty-three (47.7%) had methicillin-resistant SAB. When short-course therapy (<14 days) and intermediate-course therapy (≥14 days) were compared, the treatment failure rates (10/38 [26.3%] versus 16/73 [21.9%]) and crude mortality (7/38 [18.4%] versus 16/73 [21.9%]) did not differ significantly between the two groups. However, short-course therapy was significantly associated with relapse (3/38 [7.9%] versus 0/73; P = 0.036). In multivariate analysis, primary bacteremia was associated with a trend toward increased treatment failure (P = 0.06). Therefore, in the treatment of uncomplicated SAB, it seems reasonable to consider at least 14 days of antibiotic therapy to prevent relapse, as practice guidelines recommend. Because of its poor prognosis, primary bacteremia, even with a low risk of complication, should not be treated with short-course therapy.
PMCID: PMC3591920  PMID: 23254436
3.  Outcome and reinfection after Staphylococcus aureus bacteraemia in individuals with and without HIV-1 infection: a case–control study 
BMJ Open  2014;4(4):e004075.
Individuals infected with HIV-1 are at an increased risk of Staphylococcus aureus bacteraemia (SAB). The aim of this study was to investigate mortality rate and risk of reinfection associated with SAB in HIV-1-infected individuals compared to individuals without HIV-1 infection.
University hospital treating a third of the estimated 5000 individuals with HIV infection in Denmark.
HIV-1-infected (n=82) and sex-matched and age-matched uninfected (n=163) individuals with SAB in the time period 1 January 1995 to 31 December 2010.
Primary outcome measures
30-day and 365-day mortality rate ratio and relative risk of reinfection.
Individuals with HIV had an increased risk of death at day 30 (OR 11.90 (95% CI 2.15 to 65.85)) compared to individuals without HIV. Other factors associated with mortality were age, a foreign device and Pitt score. HIV-related factors did not associate to mortality. During follow-up, there were 43 episodes of reinfection; in individuals with HIV infection at an incidence rate of 7.8 (95% CI 4.7 to 10.9)/100 person-years compared with 2.2 (95% CI 1.2 to 3.2)/100 person-years for individuals without HIV. In multivariate analysis, HIV status (OR 2.91 (95% CI 1.29 to 6.58) and injection drug use (OR 3.51 (95% CI 1.06 to 11.63) were independently associated with an increased risk of reinfection.
HIV-1 infection is associated with an increased risk of 30-day mortality after SAB and a very high rate of reinfection. Age, a foreign device and Pitt score predicted outcome. For patients infected with HIV, neither CD4 T-lymphocyte counts nor plasma HIV RNA levels were associated with 30-day outcome.
Trial registration number
The study was approved by the Danish Data Protection Agency (record no. 2007-41-1196).
PMCID: PMC4010819  PMID: 24760348
4.  High Cell-Free DNA Predicts Fatal Outcome among Staphylococcus aureus Bacteraemia Patients with Intensive Care Unit Treatment 
PLoS ONE  2014;9(2):e87741.
Among patients with bacteraemia or sepsis the plasma cell-free DNA (cf-DNA) biomarker has prognostic value and Pitt bacteraemia scores predict outcome. We evaluated the prognostic value of plasma cf-DNA in patients with Staphylococcus aureus bacteraemia (SAB) treated in the ICU or in the general ward.
418 adult patients with positive blood culture for S. aureus were prospectively followed for 90 days. SAB patients were grouped according to ICU treatment: 99 patients were treated in ICU within 7 days of documented SAB whereas 319 patients were managed outside ICU. Pitt bacteraemia scores were assessed at hospital arrival and cf-DNA was measured at days 3 and 5 from positive blood culture.
SAB patients with high Pitt bacteraemia scores and ICU treatment presented higher cf-DNA values as compared to SAB patients with low Pitt bacteraemia scores and non-ICU treatment at both days 3 and 5. Among ICU patients cf-DNA >1.99 µg/ml at day 3 predicted death with a sensitivity of 67% and a specificity of 77% and had an AUC in receiver operating characteristic analysis of 0.71 (p<0.01). The cut-off cf-DNA >1.99 µg/ml value demonstrated a strong association to high Pitt bacteraemia scores (≥4 points) (p<0.000). After controlling for all prognostic markers, Pitt bacteraemia scores ≥4 points at hospital admission (OR 4.47, p<0.000) and day 3 cf-DNA (OR 3.56, p<0.001) were the strongest factors significantly predicting outcome in ICU patients. cf-DNA at day 5 did not predict fatal outcome.
High cf-DNA concentrations were observed among patients with high Pitt bacteraemia scores and ICU treatment. Pitt bacteraemia scores (≥4 points) and cf-DNA at day 3 from positive blood culture predicted death among SAB patients in ICU and were found to be independent prognostic markers. cf-DNA had no prognostic value among non-ICU patients.
PMCID: PMC3919733  PMID: 24520336
5.  Infectious Diseases Consultation Lowers Mortality From Staphylococcus aureus Bacteremia 
Medicine  2009;88(5):263-267.
Staphylococcus aureus bacteremia (SAB) is a lethal and increasingly common infection in hospitalized patients. We assessed the impact of infectious diseases consultation (IDC) on clinical management and hospital mortality of SAB in 240 hospitalized patients in a retrospective cohort study. Patients who received IDC were older than those who did not (57.9 vs. 51.7 yr; p = 0.05), and were more likely to have a health care-associated infection (63% vs. 45%; p < 0.01). In patients who received IDC, there was a higher prevalence of severe complications of SAB such as central nervous system involvement (5% vs. 0%, p = 0.01), endocarditis (20% vs. 2%; p < 0.01), or osteomyelitis (15.6% vs. 3.4%; p < 0.01). Patients who received IDC had closer blood culture follow-up and better antibiotic selection, and were more likely to have pus or prosthetic material removed. Hospital mortality from SAB was lower in patients who received IDC than in those who did not (13.9% vs. 23.7%; p = 0.05). In multivariate survival analysis, IDC was associated with substantially lower hazard of hospital mortality during SAB (hazard 0.46; p = 0.03). This mortality benefit accrued predominantly in patients with methicillin-resistant SAB (hazard 0.3; p < 0.01), and in patients who did not require ICU admission (hazard 0.15; p = 0.01). In conclusion, IDC is associated with reduced mortality in patients with staphylococcal bacteremia.
PMCID: PMC2881213  PMID: 19745684
6.  Impact of infectious diseases consultation on the management of Staphylococcus aureus bacteraemia in children 
BMJ Open  2014;4(7):e004659.
Infectious diseases consultation (IDC) in adults with Staphylococcus aureus bacteraemia (SAB) has been shown to improve management and outcome. The aim of this study was to evaluate the impact of IDC on the management of SAB in children.
Study design
Observational cohort study of children with SAB.
Cambridge University Hospitals National Health Service (NHS) Foundation Trust, a large acute NHS Trust in the UK.
All children with SAB admitted to the Cambridge University Hospitals NHS Foundation Trust between 16 July 2006 and 31 December 2012.
Children with SAB between 2006 and 31 October 2009 were managed by routine clinical care (pre-IDC group) and data were collected retrospectively by case notes review. An IDC service for SAB was introduced in November 2009. All children with SAB were reviewed regularly and data were collected prospectively (IDC group) until 31 December 2012. Baseline characteristics, quality metrics and outcome were compared between the pre-IDC group and IDC group.
There were 66 episodes of SAB in 63 children—28 patients (30 episodes) in the pre-IDC group, and 35 patients (36 episodes) in the IDC group. The median age was 3.4 years (IQR 0.2–10.7 years). Patients in the IDC group were more likely to have echocardiography performed, a removable focus of infection identified and to receive a longer course of intravenous antimicrobial therapy. There were no differences in total duration of antibiotic therapy, duration of hospital admission or outcome at 30 or 90 days following onset of SAB.
IDC resulted in improvements in the investigation and management of SAB in children.
PMCID: PMC4091395  PMID: 24989617
7.  Clinical manifestations and outcome in Staphylococcus aureus endocarditis among injection drug users and nonaddicts: a prospective study of 74 patients 
Endocarditis is a common complication in Staphylococcus aureus bacteremia (SAB). We compared risk factors, clinical manifestations, and outcome in a large, prospective cohort of patients with S. aureus endocarditis in injection drug users (IDUs) and in nonaddicts.
Four hundred and thirty consecutive adult patients with SAB were prospectively followed up for 3 months. Definite or possible endocarditis by modified Duke criteria was found in 74 patients: 20 patients were IDUs and 54 nonaddicts.
Endocarditis was more common in SAB among drug abusers (46%) than in nonaddicts (14%) (odds ratio [OR], 5.12; 95% confidence interval [CI], 2.65–9.91; P < 0.001). IDUs were significantly younger (27 ± 15 vs 65 ± 15 years, P < 0.001), had less ultimately or rapidly fatal underlying diseases (0% vs 37%, P < 0.001) or predisposing heart diseases (20% vs 50%, P = 0.03), and their SAB was more often community-acquired (95% vs 39%, P < 0.001). Right-sided endocarditis was observed in 60% of IDUs whereas 93% of nonaddicts had left-sided involvement (P < 0.001). An extracardiac deep infection was found in 85% of IDUs and in 89% of nonaddicts (P = 0.70). Arterial thromboembolic events and severe sepsis were also equally common in both groups. There was no difference in mortality between the groups at 7 days, but at 3 months it was lower among IDUs (10%) compared with nonaddicts (39%) (OR, 5.73; 95% CI, 1.20–27.25; P = 0.02).
S. aureus endocarditis in IDUs was associated with as high complication rates including extracardiac deep infections, thromboembolic events, or severe sepsis as in nonaddicts. Injection drug abuse in accordance with younger age and lack of underlying diseases were associated with lower mortality, but after adjusting by age and underlying diseases injection drug abuse was not significantly associated with mortality.
PMCID: PMC1584240  PMID: 16965625
8.  Heterogeneous vancomycin-intermediate susceptibility in a community-associated methicillin-resistant Staphylococcus aureus epidemic clone, in a case of Infective Endocarditis in Argentina 
Community-Associated Methicillin Resistant Staphylococcus aureus (CA-MRSA) has traditionally been related to skin and soft tissue infections in healthy young patients. However, it has now emerged as responsible for severe infections worldwide, for which vancomycin is one of the mainstays of treatment. Infective endocarditis (IE) due to CA-MRSA with heterogeneous vancomycin-intermediate susceptibility-(h-VISA) has been recently reported, associated to an epidemic USA 300 CA-MRSA clone.
Case Presentation
We describe the occurrence of h-VISA phenotype in a case of IE caused by a strain belonging to an epidemic CA-MRSA clone, distinct from USA300, for the first time in Argentina. The isolate h-VISA (SaB2) was recovered from a patient with persistent bacteraemia after a 7-day therapy with vancomycin, which evolved to fatal case of IE complicated with brain abscesses. The initial isolate-(SaB1) was fully vancomycin susceptible (VSSA). Although MRSA SaB2 was vancomycin susceptible (≤2 μg/ml) by MIC (agar and broth dilution, E-test and VITEK 2), a slight increase of MIC values between SaB1 and SaB2 isolates was detected by the four MIC methods, particularly for teicoplanin. Moreover, Sab2 was classified as h-VISA by three different screening methods [MHA5T-screening agar, Macromethod-E-test-(MET) and by GRD E-test] and confirmed by population analysis profile-(PAP). In addition, a significant increase in cell-wall thickness was revealed for SaB2 by electron microscopy. Molecular typing showed that both strains, SaB1 and SaB2, belonged to ST5 lineage, carried SCCmecIV, lacked Panton-Valentine leukocidin-(PVL) genes and had indistinguishable PFGE patterns (subtype I2), thereby confirming their isogenic nature. In addition, they were clonally related to the epidemic CA-MRSA clone (pulsotype I) detected in our country.
This report demonstrates the ability of this epidemic CA-MRSA clone, disseminated in some regions of Argentina, to produce severe and rapidly fatal infections such as IE, in addition to its ability to acquire low-level vancomycin resistance; for these reasons, it constitutes a new challenge for the Healthcare System of this country.
PMCID: PMC3111347  PMID: 21527033
9.  Persistent strong anti-HLA antibody at high titer is complement binding and associated with increased risk of antibody-mediated rejection in heart transplant recipients 
Sensitized heart transplant candidates are evaluated for donor-specific anti-HLA IgG antibody (DSA) by Luminex single-antigen bead (SAB) testing (SAB-IgG) to determine donor suitability and help predict a positive complement-dependent cytotoxicity crossmatch (CDC-XM) by virtual crossmatching (VXM). However, SAB testing used for VXM does not correlate perfectly with CDC-XM results and individual transplant programs have center-specific permissible thresholds to predict crossmatch positivity. A novel Luminex SAB-based assay detecting C1q-binding HLA antibodies (SAB-C1q) contributes functional information to SAB testing, but the relationship between SAB strength and complement-binding ability is unclear.
In this retrospective study, we identified 15 pediatric and adult heart allograft candidates with calculated panel-reactive antibody (cPRA) >50% by SAB-IgG and compared conventional SAB-IgG results with SAB-C1q testing.
Pre- and post-transplant DSA by SAB-C1q correlated with DSA by SAB-IgG and also with CDC-XM results and early post-transplant endomyocardial biopsy findings. Individual HLA antibodies by SAB-IgG in undiluted sera correlated poorly with SAB-C1q; however, when sera were diluted 1:16, SAB-IgG results were well correlated with SAB-C1q. In some sera, HLA antibodies with low mean fluorescent intensity (MFI) by SAB-IgG exhibited high SAB-C1q MFIs for the same HLA antigens. Diluting or heat-treating these sera increased SAB-IgG MFI, consistent with SAB-C1q results. In 13 recipients, SAB-C1q–positive DSA was associated with positive CDC-XM and with early clinical post-transplant antibody-mediated rejection (cAMR).
Risk assessment for positive CDC-XM and early cAMR in sensitized heart allograft recipients are correlated with SAB-C1q reactivity.
PMCID: PMC3628631  PMID: 23142561
HLA antibody; complement binding; antibody mediated rejection; heart transplantation; virtual crossmatch
10.  Genetic Variability in Beta-Defensins Is Not Associated with Susceptibility to Staphylococcus aureus Bacteremia 
PLoS ONE  2012;7(2):e32315.
Human beta-defensins are key components of human innate immunity to a variety of pathogens, including Staphylococcus aureus. The aim of the present study was to investigate a potential association between gene variations in DEFB1 and DEFB103/DEFB4 and the development of S. aureus bacteremia (SAB) employing a case-control design.
Cases were unique patients with documented SAB, identified with the National S. aureus Bacteremia Register, a comprehensive dataset of all episodes of community associated-SABs (CA-SAB) occurring in children (≤20 yrs) in Denmark from 1990 to 2006. Controls were age-matched healthy individuals with no history of SAB. DNA obtained from cases and controls using the Danish Newborn Screening Biobank were genotyped for functional polymorphisms of DEFB1 by Sanger sequencing and copy number variation of the DEFB103 and DEFB4 genes using Pyrosequencing-based Paralogue Ratio Test (P-PRT).
193 ethnic Danish SAB cases with 382 age-matched controls were used for this study. S. aureus isolates represented a variety of bacterial (i.e., different spa types) types similar to SAB isolates in general. DEFB1 minor allele frequencies of rs11362 (cases vs. controls 0.47/0.44), rs1800972 (0.21/0.24), and rs1799946 (0.32/0.33) were not significantly different in cases compared with controls. Also, DEFB4/DEFB103 gene copy numbers (means 4.83/4.92) were not significantly different in cases compared with controls.
Using a large, unique cohort of pediatric CA-SAB, we found no significant association between DEFB1 genetic variation or DEFB4/DEFB103 gene copy number and susceptibility for SAB.
PMCID: PMC3285211  PMID: 22384213
11.  Effect of Statin Therapy in the Outcome of Bloodstream Infections Due to Staphylococcus aureus: A Prospective Cohort Study 
PLoS ONE  2013;8(12):e82958.
Statins have pleiotropic effects that could influence the prevention and outcome of some infectious diseases. There is no information about their specific effect on Staphylococcus aureus bacteremia (SAB).
A prospective cohort study including all SAB diagnosed in patients aged ≥18 years admitted to a 950-bed tertiary hospital from March 2008 to January 2011 was performed. The main outcome variable was 14-day mortality, and the secondary outcome variables were 30-day mortality, persistent bacteremia (PB) and presence of severe sepsis or septic shock at diagnosis of SAB. The effect of statin therapy at the onset of SAB was studied by multivariate logistic regression and Cox regression analysis, including a propensity score for statin therapy.
We included 160 episodes. Thirty-three patients (21.3%) were receiving statins at the onset of SAB. 14-day mortality was 21.3%. After adjustment for age, Charlson index, Pitt score, adequate management, and high risk source, statin therapy had a protective effect on 14-day mortality (adjusted OR = 0.08; 95% CI: 0.01–0.66; p = 0.02), and PB (OR = 0.89; 95% CI: 0.27–1.00; p = 0.05) although the effect was not significant on 30-day mortality (OR = 0.35; 95% CI: 0.10–1.23; p = 0.10) or presentation with severe sepsis or septic shock (adjusted OR = 0.89; CI 95%: 0.27–2.94; p = 0.8). An effect on 30-day mortality could neither be demonstrated on Cox analysis (adjusted HR = 0.5; 95% CI: 0.19–1.29; p = 0.15).
Statin treatment in patients with SAB was associated with lower early mortality and PB. Randomized studies are necessary to identify the role of statins in the treatment of patients with SAB.
PMCID: PMC3871563  PMID: 24376617
12.  Stable incidence and continued improvement in short term mortality of Staphylococcus aureus bacteraemia between 1995 and 2008 
BMC Infectious Diseases  2012;12:260.
The objective of this study was to assess temporal changes in incidence and short term mortality of Staphylococcus aureus bacteraemia (SAB) from 1995 through 2008.
The study was conducted as a nation-wide observational cohort study with matched population controls. The setting was hospitalized patients in Denmark 1995-2008. Uni- and multivariate analyses were used to analyze the hazard of death within 30 days from SAB.
A total of 16 330 cases of SAB were identified: 57% were hospital-associated (HA), 31% were community-acquired (CA) and 13% were of undetermined acquisition. The overall adjusted incidence rate remained stable at 23 per 100 000 population but the proportion of SAB cases older than 75 years increased significantly. Comorbidity in the cohort as measured by Charlson comorbidity index (CCI) score and alcohol-related diagnoses increased over the study period. In contrast, among the population controls the CCI remained stable and alcohol-related diagnoses increased slightly. For HA SAB crude 30-day mortality decreased from 27.8% to 21.8% (22% reduction) whereas the change for CA SAB was small (26.5% to 25.8%). By multivariate Cox regression, age, female sex, time period, CCI score and alcohol-related diagnoses were associated with increased mortality regardless of mode of acquisition.
Throughout a 14-year period the overall incidence of SAB remained stable while the overall short term prognosis continued to improve despite increased age and accumulation of comorbidity in the cohort. However, age and comorbidity were strong prognostic indicators for short term mortality.
PMCID: PMC3507819  PMID: 23075215
Bacteraemia; Epidemiology; Incidence; Mortality; Comorbidity; Alcoholism; Staphylococcus aureus; Charlson comorbidity index
13.  A genome-wide association study of variants associated with acquisition of Staphylococcus aureus bacteremia in a healthcare setting 
Humans vary in their susceptibility to acquiring Staphylococcus aureus infection, and research suggests that there is a genetic basis for this variability. Several recent genome-wide association studies (GWAS) have identified variants that may affect susceptibility to infectious diseases, demonstrating the potential value of GWAS in this arena.
We conducted a GWAS to identify common variants associated with acquisition of S. aureus bacteremia (SAB) resulting from healthcare contact. We performed a logistic regression analysis to compare patients with healthcare contact who developed SAB (361 cases) to patients with healthcare contact in the same hospital who did not develop SAB (699 controls), testing 542,410 SNPs and adjusting for age (by decade), sex, and 6 significant principal components from our EIGENSTRAT analysis. Additionally, we evaluated the joint effect of the host and pathogen genomes in association with severity of SAB infection via logistic regression, including an interaction of host SNP with bacterial genotype, and adjusting for age (by decade), sex, the 6 significant principal components, and dialysis status. Bonferroni corrections were applied in both analyses to control for multiple comparisons.
Ours is the first study that has attempted to evaluate the entire human genome for variants potentially involved in the acquisition or severity of SAB. Although this study identified no common variant of large effect size to have genome-wide significance for association with either the risk of acquiring SAB or severity of SAB, the variant (rs2043436) most significantly associated with severity of infection is located in a biologically plausible candidate gene (CDON, a member of the immunoglobulin family) and may warrant further study.
The genetic architecture underlying SAB is likely to be complex. Future investigations using larger samples, narrowed phenotypes, and advances in both genotyping and analytical methodologies will be important tools for identifying causative variants for this common and serious cause of healthcare-associated infection.
PMCID: PMC3928605  PMID: 24524581
Genomics; Genome-wide association study; Case–control study; Staphylococcus aureus; Bacteremia; Gram-positive bacterial infections; Polymorphism, single-nucleotide; Infections; Nosocomial; Cross infection
14.  Impact of Methicillin-Resistance on Mortality in Children and Neonates with Staphylococcus aureus Bacteremia: A Meta-analysis 
Infection & Chemotherapy  2013;45(2):202-210.
Staphylococcus aureus bacteremia (SAB) is the Staphylococcal infections in blood, one of the most common and fatal bacterial infectious diseases worldwide in adults as well as children or neonates. Recently, some studies have yielded inconsistent findings about the association between methicillin-resistance and mortality in patients with SAB. We performed a meta-analysis to assess the impact of methicillin-resistance on mortality in children or neonates with S. aureus bacteremia.
Materials and Methods
We searched using electronic databases such as Ovid-Medline, EMBASE-Medline, and Cochrane Library, as well as five local databases for published studies during the period of 1 January 2000 to 15 September 2011. Two reviewers independently selected articles in accordance with predetermined criteria and extracted prespecified data based on standardized forms. All cohort studies, which compared in-hospital mortality or SAB-related mortality in children and neonates with methicillin-resistant S. aureus (MRSA) infection to those with methicillin-susceptible S. aureus (MSSA), were included. We conducted meta-analysis using the fixed-effect model to obtain pooled estimates of effect.
Of 2,841 screened studies, seven cohort studies were finally selected for analysis. In children or neonates, MRSA bacteremia was associated with a higher mortality compared with MSSA bacteremia (pooled odds ratio [OR] 2.33, P = 0.0008, 95% confidence interval [CI] 1.42 to 3.82, I2 = 0%). Four studies reported SAB-related mortality, the pooled OR of these studies was 2.03 (P = 0.29, 95% CI 0.55 to 7.53, I2 = 0%). A significant increase in mortality associated with methicillin resistance was found in the subgroup analyses of the studies with only neonates (OR: 2.66, 95% CI: 1.46 to 4.85, P = 0.001), prospectively design ones (OR: 3.20, 95% CI: 1.66 to 6.15, P = 0.0005,), the larger studies (OR: 2.89, 95% CI: 1.62 to 5.16, P = 0.0003) and the higher quality studies (OR: 2.76, 95% CI: 1.50 to 5.06, P = 0.001).
MRSA bacteremia is associated with increased mortality compared with MSSA bacteremia in children or neonates. Due to limited studies for mortality in children or neonates with SAB, further research is needed to evaluate the impact of methicillin resistance on mortality in those populations.
PMCID: PMC3780954  PMID: 24265968
Staphylococcus aureus; Bacteremia; Methicillin Resistance; Mortality; Meta-analysis
15.  Predictors of Mortality in Staphylococcus aureus Bacteremia 
Clinical Microbiology Reviews  2012;25(2):362-386.
Summary: Staphylococcus aureus bacteremia (SAB) is an important infection with an incidence rate ranging from 20 to 50 cases/100,000 population per year. Between 10% and 30% of these patients will die from SAB. Comparatively, this accounts for a greater number of deaths than for AIDS, tuberculosis, and viral hepatitis combined. Multiple factors influence outcomes for SAB patients. The most consistent predictor of mortality is age, with older patients being twice as likely to die. Except for the presence of comorbidities, the impacts of other host factors, including gender, ethnicity, socioeconomic status, and immune status, are unclear. Pathogen-host interactions, especially the presence of shock and the source of SAB, are strong predictors of outcomes. Although antibiotic resistance may be associated with increased mortality, questions remain as to whether this reflects pathogen-specific factors or poorer responses to antibiotic therapy, namely, vancomycin. Optimal management relies on starting appropriate antibiotics in a timely fashion, resulting in improved outcomes for certain patient subgroups. The roles of surgery and infectious disease consultations require further study. Although the rate of mortality from SAB is declining, it remains high. Future international collaborative studies are required to tease out the relative contributions of various factors to mortality, which would enable the optimization of SAB management and patient outcomes.
PMCID: PMC3346297  PMID: 22491776
16.  Use of a Simple Criteria Set for Guiding Echocardiography in Nosocomial Staphylococcus aureus Bacteremia 
A set of simple clinical prediction criteria for patients with nosocomial Staphylococcus aureus bacteremia was developed to identify patients at low risk of infective endocarditis in whom transesophageal echocardiography might be dispensable and was validated with two independent cohorts.
(see the editorial commentary and Soriano and Mensa, on pages 10–12.)
Background. Infective endocarditis (IE) is a severe complication in patients with nosocomial Staphylococcus aureus bacteremia (SAB). We sought to develop and validate criteria to identify patients at low risk for the development of IE in whom transesophageal echocardiography (TEE) might be dispensable.
Methods. Consecutive patients with nosocomial SAB from independent cohorts in Europe (Invasive S. aureus Infection Cohort [INSTINCT]) and North America (S. aureus Bacteremia Group [SABG]) were evaluated for the presence of clinical criteria predicting an increased risk for the development of IE (ie, prolonged bacteremia of >4 days' duration, presence of a permanent intracardiac device, hemodialysis dependency, spinal infection, and nonvertebral osteomyelitis). Patients were observed closely for clinical signs and symptoms of IE during hospitalization and a 3-month follow-up period.
Results. IE was present in 13 (4.3%) of 304 patients in the INSTINCT cohort and in 40 (9.3%) of 432 patients in the SABG cohort. Within 14 days after the first positive blood culture result, echocardiography was performed in 39.8% and 57.4% of patients in the INSTINCT and SABG cohorts, respectively. In patients with IE, the most common clinical prediction criteria present were prolonged bacteremia (69.2% vs 90% for INSTINCT vs SABG, respectively) and presence of a permanent intracardiac device (53.8% vs 32.5%). In total, 13 of 13 patients in the INSTINCT cohort and 39 of 40 patients in the SABG cohort with documented IE fulfilled at least 1 criterion (sensitivity, 100% vs. 97.5%; negative predictive value, 100% vs 99.2%).
Conclusions. A simple criteria set for patients with nosocomial SAB can identify patients at low risk of IE. Patients who meet these criteria may not routinely require TEE.
PMCID: PMC3149212  PMID: 21653295
17.  Outcome of Vancomycin Treatment in Patients with Methicillin-Susceptible Staphylococcus aureus Bacteremia▿  
Limited data on the clinical outcome of vancomycin treatment compared with that of beta-lactam treatment in patients with methicillin-susceptible Staphylococcus aureus bacteremia (MSSA-B) are available. We used different and complementary approaches: (i) a retrospective cohort study using a propensity score to adjust for confounding by treatment assignment and (ii) a matched case-control study. Of all patients with S. aureus bacteremia (SAB) in two university-affiliated hospitals over a 7-year period, 294 patients with MSSA-B were enrolled in the cohort study. The cases for the case-control study were defined as patients who received vancomycin treatment for MSSA-B; the controls, who were patients that received beta-lactam treatment for MSSA-B, were selected at a 1:2 (case:control) ratio according to the objective matching scoring system and the propensity score system. In the cohort study, SAB-related mortality in patients with vancomycin treatment (37%, 10/27) was significantly higher than that in those with beta-lactam treatment (18%, 47/267) (P = 0.02). In addition, multivariate analysis revealed that vancomycin treatment was associated with SAB-related mortality when independent predictors for SAB-related mortality and propensity score were considered (adjusted odds ratio of 3.3, 95% confidence interval of 1.2 to 9.5). In the case-control study using the objective matching scoring system and the propensity score system, SAB-related mortality in case patients was 37% (10/27) and in control patients 11% (6/54) (P < 0.01). Our data suggest that vancomycin is inferior to beta-lactam in the treatment of MSSA-B.
PMCID: PMC2223910  PMID: 17984229
18.  Health Care–Associated Native Valve Endocarditis in Patients with no History of Injection Drug Use: Current Importance of Non-Nosocomial Acquisition 
Annals of internal medicine  2009;150(9):586-594.
The clinical profile and outcome of nosocomial and non-nosocomial health care–associated native valve endocarditis are not well defined.
To describe the prevalence, clinical characteristics, and outcomes of nosocomial and non-nosocomial health care–associated native valve endocarditis.
Prospective observational study.
61 hospitals in 28 countries.
Patients with definite native valve endocarditis and no history of injection drug use who were enrolled in the International Collaboration on Endocarditis–Prospective Cohort Study from June 2000 to August 2005.
Characteristics of nosocomial and non-nosocomial health care–associated native valve endocarditis cases were described and compared with those cases acquired in the community.
Health care–associated native valve endocarditis was present in 557 (34%) of 1622 patients with native valve endocarditis and no history of injection drug use (nosocomial native valve endocarditis 303 patients [54%]; non-nosocomial health care–associated native valve endocarditis 254 patients [46%]). Staphylococcus aureus was the most common cause of health care-associated native valve endocarditis (nosocomial native valve endocarditis, 47%; non-nosocomial health care–associated native valve endocarditis, 42%; p=0.3), with a notable proportion of methicillin-resistant S. aureus (nosocomial native valve endocarditis, 57%; non-nosocomial health care–associated native valve endocarditis, 41%; p=0.014). Patients with health care–associated native valve endocarditis had lower rates of cardiac surgery (41% health care–associated native valve endocarditis vs 51% community-acquired native valve endocarditis, p<0.001) and higher in-hospital mortality rates than patients with community-acquired native valve endocarditis (25% health care–associated native valve endocarditis vs. 13% community-acquired native valve endocarditis vs., p<0.001). Multivariable analysis confirmed a higher mortality associated with health care–associated native valve endocarditis (incidence risk ratio=1.20 (CI 95%, 1.03–1.61).
This study involves tertiary hospitals with cardiac surgery programs. The results may not be generalized to patient populations receiving care in other types of facility.
More than one-third of all cases of native valve endocarditis in non-drug users involve contact with health care. S. aureus is the leading cause of health care–associated native valve endocarditis. Non-nosocomial health care–associated native valve endocarditis is common, especially in the US. Patients with health care-associated and community-acquired native valve endocarditis differ in their presentation, microbiology, and outcome. By contrast, patients with nosocomial and non-nosocomial healthcare-associated endocarditis are similar.
PMCID: PMC3625649  PMID: 19414837
infective endocarditis; healthcare-associated endocarditis; nosocomial endocarditis; non-nosocomial healthcare-associated endocarditis; community-acquired endocarditis; Staphylococcal aureus endocarditis; MRSA endocarditis; Coagulase-negative staphylococcal endocarditis; Surgery; Outcome
19.  Analysis of Methicillin Resistance among Staphylococcus aureus Blood Isolates in an Emergency Department 
Journal of Korean Medical Science  2007;22(4):682-686.
The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) has become of great concern in both hospital and community settings. To evaluate the prevalence and risk factors for methicillin resistance among Staphylococcus aureus, blood isolates in our Emergency Department (ED) were collected. All patients with S. aureus bacteremia (SAB) who presented to the ED from January 2000 to August 2005 were included, and a retrospective study was performed. A total of 231 patients with SAB were enrolled (median age, 59 yr; M:F, 125:106). Among these patients, methicillin-resistant strains accounted for 27.3% (63 patients). Catheter-related infection was the most frequent primary site of SAB (39.0%), followed by skin and soft tissue infection (16.5%). In multivariate analysis, recent surgery (OR, 3.41; 95% CI, 1.48-7.85), recent hospitalization (2.17; 1.06-4.62), and older age (≥61 yr) (2.39; 1.25-4.57) were independently associated with the acquisition of methicillin-resistant strains. When antimicrobial therapy is considered for the treatment of a patient with suspected SAB, clinicians should consider obtaining cultures and modifying empirical therapy to provide MRSA coverage for patients with risk factors: older age, recent hospitalization, and recent surgery.
PMCID: PMC2693820  PMID: 17728510
Staphylococcus aureus; Community-acquired Infections; Methicillin Resistance; Risk Factors
20.  Community-based outpatient parenteral antimicrobial therapy (CoPAT) for Staphylococcus aureus bacteraemia with or without infective endocarditis: analysis of the randomized trial comparing daptomycin with standard therapy 
Administering outpatient parenteral antimicrobial therapy in the community setting (CoPAT) is becoming more common with the increasing emphasis on controlling costs. However, few controlled trials have evaluated this treatment modality.
Using data from a recent randomized trial comparing daptomycin with standard therapy (semi-synthetic penicillin or vancomycin, each with initial low-dose gentamicin) for Staphylococcus aureus bacteraemia and infective endocarditis (SAB/IE), patient characteristics and outcomes were evaluated. Patients receiving their full course of therapy in the hospital setting were compared with those who received some portion outside of the hospital (CoPAT).
Among the 200 patients, 51.5% received CoPAT. These patients were generally younger (median age 50 versus 54 years, P = 0.028). In the CoPAT group, there tended to be fewer patients with endocardial involvement (8.7% versus 18.6%, P = 0.061) and pre-existing valvular heart disease (7.8% versus 15.5%, P = 0.120). CoPAT patients received longer therapy courses (mean 25.4 versus 13.5 days, P < 0.001) and had higher rates of therapy completion (90.3% versus 45.4%, P < 0.001) and clinical success (86.4% versus 55.7%, P < 0.001). Persisting or relapsing S. aureus was less frequent in the CoPAT group (3.9% versus 15.5%, P = 0.007) and there were fewer deaths (3.9% versus 18.6%, P = 0.001) 6 weeks after the end of therapy. Hospital readmission occurred for 18 of the 103 (17.5%) CoPAT patients. Clinical success rates were similar for CoPAT patients receiving daptomycin (90.0%) or standard therapy (83.0%).
With proper monitoring, stable patients can complete treatment for SAB/IE as outpatients in the community setting. Daptomycin is an appropriate option for this setting.
PMCID: PMC2667135  PMID: 19264792
outcomes; hospital readmission; OPAT; vancomycin; semi-synthetic penicillin
21.  Helicobacter pylori outer membrane proteins and gastroduodenal disease 
Gut  2006;55(6):775-781.
Background and aims
A number of Helicobacter pylori outer membrane proteins (OMPs) undergo phase variations. This study examined the relation between OMP phase variations and clinical outcome.
Expression of H pylori BabA, BabB, SabA, and OipA proteins was determined by immunoblot. Multiple regression analysis was performed to determine the relation among OMP expression, clinical outcome, and mucosal histology.
H pylori were cultured from 200 patients (80 with gastritis, 80 with duodenal ulcer (DU), and 40 with gastric cancer). The most reliable results were obtained using cultures from single colonies of low passage number. Stability of expression with passage varied with OipA > BabA > BabB > SabA. OipA positive status was significantly associated with the presence of DU and gastric cancer, high H pylori density, and severe neutrophil infiltration. SabA positive status was associated with gastric cancer, intestinal metaplasia, and corpus atrophy, and negatively associated with DU and neutrophil infiltration. The Sydney system underestimated the prevalence of intestinal metaplasia/atrophy compared with systems using proximal and distal corpus biopsies. SabA expression dramatically decreased following exposure of H pylori to pH 5.0 for two hours.
SabA expression frequently switched on or off, suggesting that SabA expression can rapidly respond to changing conditions in the stomach or in different regions of the stomach. SabA positive status was inversely related to the ability of the stomach to secrete acid, suggesting that its expression may be regulated by changes in acid secretion and/or in antigens expressed by the atrophic mucosa.
PMCID: PMC1856239  PMID: 16322107
Helicobacter pylori; outer membrane proteins; SabA; OipA; BabA
22.  New Approaches to the Diagnosis and Treatment of Infective Endocarditis 
Texas Heart Institute Journal  1989;16(4):250-257.
To assess the effect of our new, more aggressive approach to treating infective endocarditis, we retrospectively reviewed our recent experience with this disease. Between 1983 and 1989, we treated 100 patients with endocarditis, in 94 of whom the diagnosis was confirmed. Fifty-four (57%) of the 94 patients had native valve endocarditis, and the other 40 patients (43%) had prosthetic valve endocarditis. The patients' mean ages were 50 years for native valve disease and 58 years for prosthetic valve disease (p < 0.05). The male-to-female ratio was 4:1. Among the patients with confirmed endocarditis, 87 (93%) had significant underlying risk factors for endocarditis. Upon physical examination of the 94 patients, 16 (17%) were afebrile, 15 (16%) had negative blood cultures, and 26 (28%) had no cardiovascular symptoms or immunologic findings. Echocardiography was of limited value: its sensitivity was 56% for native valve endocarditis and 33% for prosthetic valve endocarditis. The ratio of affected valves was 5 aortic:4 mitral: 1 tricuspid in both forms of the disease. Viridans streptococcus was isolated in 23 (25%) of the confirmed cases, Enterococcus faecalis in 17 (18%), Staphylococcus aureus in 13 (14%), and coagulase-negative staphylococcus in 14 (15%). Gram-negative, anaerobic, and fungal organisms accounted for only 13 (14%) of the confirmed cases.
The mean duration of intravenous therapy was 29 days. Twenty (37%) of the native valve patients and 16 (40%) of the prosthetic valve patients received antibiotics on an outpatient basis. Vancomycin was used in 44 (47%) of the cases, nafcillin or ampicillin in 40 (44%), and other β-lactam agents in 9 (10%). The mean hospital stay was significantly longer for prosthetic valve endocarditis patients than for those with native valve disease (29 versus 23 days; p < 0.01). Cardiac catheterization was performed in 9 native valve patients (17%) and 6 prosthetic valve patients (15%). Valve surgery was performed in 33 native valve patients (61%) and 22 prosthetic valve patients (55%). Failure, defined as in-hospital death or recurrent endocarditis, accounted for 14 (28%) of the native valve cases (17% death and 11% relapse) and 8 (20%) of the prosthetic valve cases (10% death and 10% relapse), for an overall failure rate of 24%. The rate of failure was independent of the infecting pathogen or the type of antimicrobial therapy applied. Our experience verified that, in many patients with significant underlying risk factors, the diagnosis of endocarditis may be made on an empiric basis. (Texas Heart Institute Journal 1989;16:250-7)
PMCID: PMC326529  PMID: 15227377
Antibiotics; diagnosis; endocarditis, infective; heart valve diseases; heart valve prosthesis; infection
23.  Temporal Trends in Incidence of Staphylococcus aureus Bacteremia in Olmsted County, Minnesota, 1998 to 2005: A Population-Based Study 
There is a paucity of population-based studies on Staphylococcus aureus bacteremia (SAB) in the United States. We determined the incidence and trends of SAB in Olmsted County, Minnesota, over an 8-year period.
A retrospective, population-based, cohort study was done to evaluate the initial episodes of SAB occurring in adult residents of Olmsted County, Minnesota, from January 1, 1998 through December 31, 2005 using the microbiology databases at Mayo Clinic and Olmsted Medical Center.
Among 247 evaluable adult patients with SAB, who were included in the incidence calculation, 57.9% were males and the median age was 72.1 years (range 19.5 - 98.5). Bacteremic episodes were classified according to acquisition site: 23.5% were nosocomial (NA-SAB); 58.7% were healthcare-associated (HCA-SAB); and 23.8% were community-acquired (CA-SAB). MRSA constituted 31.6% of the cases. No community-acquired MRSA bacteremia was noted. The age-adjusted incidence rate of SAB was 28.3/100,000 person-years for females, and 53.5/100,000 person-years for males, with an age- and gender-adjusted rate of 38.2/100,000 person-years. The age- and gender-adjusted incidence of NA-SAB, HCA-SAB, and CA-SAB was 9.0, 22.6 and 6.6/100,000 person-years, respectively. The age- and gender-adjusted incidence of MSSA was 25.4/100,000 and of MRSA was 12.4/100,000 person-years. Overall, the incidence rate increased with age, but not over calendar year. The exception was MRSA-B, which increased at a rate of 19.8% (± 5.5%) per year during the study period.
The incidence of SAB in adults remained stable in Olmsted County, Minnesota, from 1998 to 2005, but the proportion due to MRSA has significantly increased over the 8-year period.
PMCID: PMC3050712  PMID: 19916797
Incidence; Staphylococcus aureus; bacteremia; population-based; Olmsted County
24.  Association of Mannose-Binding Lectin 2 Gene Polymorphisms with Persistent Staphylococcus aureus Bacteremia 
PLoS ONE  2014;9(3):e89139.
Mannose-binding lectin (MBL) is an important component of innate immunity. Structural and promoter polymorphisms in the MBL2 gene that are responsible for low MBL levels are associated with susceptibility to infectious diseases. The objective of this study was to investigate the association of serum MBL levels and MBL2 polymorphisms with persistent Staphylococcus aureus bacteremia (SAB) in adult Korean patients.
We conducted a case-control study nested in a prospective cohort of patients with SAB. The study compared 41 patients with persistent bacteremia (≥7 days) and 46 patients with resolving bacteremia (<3 days). In each subject, we genotyped six single-nucleotide polymorphisms in the promoter region (alleles H/L, X/Y, and P/Q) and exon 1 (alleles A/B, A/C, and A/D) of the MBL2 gene and measured serum MBL concentrations. We also compared MBL2 genotypes between SAB patients and healthy people.
Patients with persistent bacteremia were significantly more likely to have low/deficient MBL-producing genotypes and resultant low serum MBL levels, than were patients with resolving bacteremia (P = 0.019 and P = 0.012, respectively). Independent risk factors for persistent bacteremia were metastatic infection (adjusted odds ratio [aOR], 34.7; 95% confidence interval [CI], 12.83–196.37; P = 0.003), methicillin resistance (aOR, 4.10; 95% CI, 3.19–29.57; P = 0.025), and low/deficient MBL-producing genotypes (aOR, 7.64; 95% CI, 4.12–63.39; P = 0.003). Such genotypes were significantly more common in patients with persistent bacteremia than in healthy people (OR, 2.09; 95% CI, 1.03–4.26; P = 0.040).
This is the first demonstration of an association of low MBL levels and MBL2 polymorphisms responsible for low or deficient MBL levels with persistent SAB. A combination of factors, including clinical and microbiological characteristics and host defense factors such as MBL levels, may together contribute to the development of persistent SAB.
PMCID: PMC3942407  PMID: 24595015
25.  Clinical and Microbiological Determinants of Outcome in Staphylococcus aureus Bacteraemia 
Staphylococcus aureus bacteraemia (SAB) is commonly complicated by metastatic infection or relapse after treatment. Objectives. The study aim was to determine the role of bacterial, host, and management factors in development of complicated SAB. Methods. A prospectively-conducted observational study gathered data on predisposition, management and outcome of 100 consecutive SAB cases. Antibiotic susceptibilities and genetic lineage of bacterial isolates were determined. Further clinical and microbiological data were gathered on two retrospective series from 1999–2000 (n = 57) and 2004 (n = 116). Results. In the prospective cases, 27% met our definition of complicated disease. Expressed as RR and 95% CI, complicated disease was associated with diabetes (1.58, 1.00–2.48), injecting-drug use (5.48, 0.88–33.49), community-onset of symptoms (1.4, 1.02–1.92), and symptom duration ≥48 hours prior to starting effective antibiotic therapy (2.10, 1.22–3.61). Uncomplicated disease was associated with the presence of a central line (0.69, 0.55–0.88) and prompt removal of a primary focus (0.71, 0.57–0.90). Neither methicillin resistance nor genetic lineage was associated with complicated disease, but methicillin resistance was associated with higher mortality. Conclusions. This study demonstrates that clinical rather than microbial factors are the major determinants of SAB outcome and underscores the importance of early treatment.
PMCID: PMC2840372  PMID: 20300477

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