Risk factors for colonization with methicillin-resistant Staphylococcus aureus (MRSA) in patients admitted to an urban hospital: emergence of community-associated MRSA nasal carriage

A case control study of environmental and occupational exposures associated with methicillin resistant Staphylococcus aureus nasal carriage in patients admitted to a rural tertiary care hospital in a high density swine region

BACKGROUND

Distinct strains of methicillin resistant Staphylococcus aureus (MRSA) have been identified on livestock and livestock workers. Industrial food animal production may be an important environmental reservoir for human carriage of these pathogenic bacteria. The objective of this study was to investigate environmental and occupational exposures associated with nasal carriage of MRSA in patients hospitalized at Vidant Medical Center, a tertiary hospital serving a region with intensive livestock production in eastern North Carolina.

METHODS

MRSA nasal carriage was identified via nasal swabs collected within 24 hours of hospital admission. MRSA carriers (cases) were gender and age matched to non-carriers (controls). Participants were interviewed about recent environmental and occupational exposures. Home addresses were geocoded and publicly available data were used to estimate the density of swine in residential census block groups of residence. Conditional logistic regression models were used to derive odds ratio (OR) estimates and 95% confidence intervals (CI). Presence of the scn gene in MRSA isolates was assessed. In addition, multi locus sequence typing (MLST) of the MRSA isolates was performed, and the Diversilab® system was used to match the isolates to USA pulsed field gel electrophoresis types.

RESULTS

From July - December 2011, 117 cases and 119 controls were enrolled. A higher proportion of controls than cases were current workforce members (41.2% vs. 31.6%) Cases had a higher odds of living in census block groups with medium densities of swine (OR: 4.76, 95% CI: 1.36-16.69) and of reporting the ability to smell odor from a farm with animals when they were home (OR: 1.51, 95% CI: 0.80-2.86). Of 49 culture positive MRSA isolates, all were scn positive. Twenty-two isolates belonged to clonal complex 5.

CONCLUSIONS

Absence of livestock workers in this study precluded evaluation of occupational exposures. Higher odds of MRSA in medium swine density areas could reflect environmental exposure to swine or poultry.

Risk factors for intensive care unit acquired nasal colonization of MRSA and its impact on MRSA infection

OBJECTIVE

We aimed to determine the risk factors of methicillin-resistant Staphylococcus aureus (MRSA) colonization, and the impact of colonization on MRSA infection to evaluate the necessity of MRSA survey program in intensive care units (ICUs) in Turkey.

METHODS

The patients hospitalized in medical and neurosurgical ICUs longer than 24 hr were included into the study. To determine anterior nares MRSA colonization, swabs were taken from each patient in the first 48 hr, and followed by once a week till discharge from ICUs.

RESULTS

During the one-year follow-up period, the number of the hospitalized patients who spent more than 24 hr in ICUs was 195 of 372 and 85 of 619 in medical and neurosurgical ICUs, respectively. Totally, 23 out of 280 patients (14 from medical ICU, 9 from neurosurgical ICU) were colonized with MRSA, and 11 out of 23 colonized patients were accepted as ICU-acquired infection. The duration of ICU hospitalization in patients with ICU-acquired MRSA colonization was found to be longer than the noncolonized patients (18 days vs. 8 days, P value < 0.001). The presence of gastrostomy and femoral catheter were determined as risk factors for ICU-acquired MRSA colonization. The percentages of MRSA infection in patients with and without MRSA colonized were 8.6% and 1.1%, respectively (P value: 0.009).

CONCLUSION

The presence of gastrostomy and femoral catheter, and the duration of ICU hospitalization were found to be related with ICU-acquired MRSA colonization. Also, MRSA nares colonization increased the rates of both MRSA infection and ICU hospitalization.

Prevalence and incidence of antimicrobial-resistant organisms among hospitalized inflammatory bowel disease patients

BACKGROUND

Patients with inflammatory bowel disease (IBD) experience frequent hospitalizations and use of immunosuppressive medications, which may predispose them to colonization with antimicrobial-resistant organisms (ARO).

OBJECTIVE

To determine the prevalence of ARO colonization on admission to hospital and the incidence of infection during hospitalization among hospitalized IBD patients.

METHODS

A chart review comparing the prevalence of colonization and incidence of infection with methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci and extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL) in hospitalized IBD patients with those of non-IBD controls was performed.

RESULTS

On admission, there were no significant differences between IBD inpatients and controls in the prevalence of colonization of methicillin-resistant S aureus (1.0% versus 1.2%; P=0.74), vancomycin-resistant enterococci (0.2% versus 0%; P=1.0) or ESBL (4.1% versus 5.5%; P=0.33). Pooling data from historical clinic-based cohorts, IBD patients were more likely than controls to have ESBL colonization (19% versus 6.6%; P<0.05). Antibiotic use on admission was associated with ESBL colonization among IBD inpatients (OR 4.2 [95% CI 1.4 to 12.6]). The incidence of ARO infections during hospitalization was not significantly different between IBD patients and controls. Among IBD patients who acquired ARO infections during hospitalizations, the mean time interval from admission to infection was shorter for those who were already colonized with ARO on admission.

CONCLUSIONS

This particular population of hospitalized IBD patients was not shown to have a higher prevalence or incidence of ARO colonization or infection compared with non-IBD inpatients.

Predictive value of methicillin-resistant Staphylococcus aureus (MRSA) nasal swab PCR assay for MRSA pneumonia

Pneumonia due to methicillin-resistant Staphylococcus aureus (MRSA) is associated with poor outcomes and frequently merits empirical antibiotic consideration despite its relatively low incidence. Nasal colonization with MRSA is associated with clinical MRSA infection and can be reliably detected using the nasal swab PCR assay. In this study, we evaluated the performance of the nasal swab MRSA PCR in predicting MRSA pneumonia. A retrospective cohort study was performed in a tertiary care center from January 2009 to July 2011. All patients with confirmed pneumonia who had both a nasal swab MRSA PCR test and a bacterial culture within predefined time intervals were included in the study. These data were used to calculate sensitivity, specificity, positive predictive value, and negative predictive value for clinically confirmed MRSA pneumonia. Four hundred thirty-five patients met inclusion criteria. The majority of cases were classified as either health care-associated (HCAP) (54.7%) or community-acquired (CAP) (34%) pneumonia. MRSA nasal PCR was positive in 62 (14.3%) cases. MRSA pneumonia was confirmed by culture in 25 (5.7%) cases. The MRSA PCR assay demonstrated 88.0% sensitivity and 90.1% specificity, with a positive predictive value of 35.4% and a negative predictive value of 99.2%. In patients with pneumonia, the MRSA PCR nasal swab has a poor positive predictive value but an excellent negative predictive value for MRSA pneumonia in populations with low MRSA pneumonia incidence. In cases of culture-negative pneumonia where initial empirical antibiotics include an MRSA-active agent, a negative MRSA PCR swab can be reasonably used to guide antibiotic de-escalation.

Predictors of methicillin-resistant Staphylococcus aureus colonization at hospital admission

BACKGROUND

The best strategy for active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) remains unclear. We attempted to identify a risk factor score to predict MRSA colonization at hospital admission.

METHODS

Data on 9 variables reported as risk factors for MRSA colonization were analyzed, and a risk factor score to predict MRSA colonization was generated using multivariable logistic regression and receiver operating characteristic curve analyses. This risk score was then prospectively validated.

RESULTS

Four risk factors (nursing home residence, diabetes, hospitalization in the past year, and chronic skin condition/infection) were significantly associated with MRSA colonization (c-statistic = 0.846). A cut-off score of 8 or greater would result in screening 20% of admissions and would detect 71% of MRSA-colonized patients. In the prospective validation study, a cut-off score of 8 or greater required screening 21% of admissions and detected 54% of MRSA. Nursing home residence was the best predictor of MRSA colonization.

CONCLUSION

A similar risk factor-based screening strategy could be used to predict MRSA colonization in other institutions. Our data support routine screening of nursing home patients at hospital admission.

Methicillin-resistant Staphylococcus aureus colonization of the groin and risk for clinical infection among HIV-infected adults

Data on the interaction between methicillin-resistant Staphylococcus aureus (MRSA) colonization and clinical infection are limited. During 2007–2008, we enrolled HIV-infected adults in Atlanta, Georgia, USA, in a prospective cohort study. Nares and groin swab specimens were cultured for S. aureus at enrollment and after 6 and 12 months. MRSA colonization was detected in 13%–15% of HIV-infected participants (n = 600, 98% male) at baseline, 6 months, and 12 months. MRSA colonization was detected in the nares only (41%), groin only (21%), and at both sites (38%). Over a median of 2.1 years of follow-up, 29 MRSA clinical infections occurred in 25 participants. In multivariate analysis, MRSA clinical infection was significantly associated with MRSA colonization of the groin (adjusted risk ratio 4.8) and a history of MRSA infection (adjusted risk ratio 3.1). MRSA prevention strategies that can effectively prevent or eliminate groin colonization are likely necessary to reduce clinical infections in this population.

Epidemiological interpretation of studies examining the effect of antibiotic usage on resistance

Bacterial resistance to antibiotics is a growing clinical problem and public health threat. Antibiotic use is a known risk factor for the emergence of antibiotic resistance, but demonstrating the causal link between antibiotic use and resistance is challenging. This review describes different study designs for assessing the association between antibiotic use and resistance and discusses strengths and limitations of each. Approaches to measuring antibiotic use and antibiotic resistance are presented. Important methodological issues such as confounding, establishing temporality, and control group selection are examined.

Methicillin-resistant Staphylococcus aureus colonization among pediatric health care workers from different outpatient settings

Staphylococcus aureus colonization rates in pediatric health care workers from different types of outpatient settings were determined from December 2008 through May 2010. Colonization rates for Staphylococcus aureus and, specifically, methicillin-resistant Staphylococcus aureus (MRSA) rates were similar to the rates that have been reported for the general population. The predominant MRSA pulsed-field gel electrophoresis type associated with colonization in these health care workers is not MRSA USA300.

Medical and household characteristics associated with methicillin resistant Staphylococcus aureus nasal carriage among patients admitted to a rural tertiary care hospital

BACKGROUND

Methicillin resistant Staphylococcus aureus (MRSA) poses a threat to patient safety and public health. Understanding how MRSA is acquired is important for prevention efforts. This study investigates risk factors for MRSA nasal carriage among patients at an eastern North Carolina hospital in 2011.

METHODS

Using a case-control design, hospitalized patients ages 18 - 65 years were enrolled between July 25, 2011 and December 15, 2011 at Vidant Medical Center, a tertiary care hospital that screens all admitted patients for nasal MRSA carriage. Cases, defined as MRSA nasal carriers, were age and gender matched to controls, non-MRSA carriers. In-hospital interviews were conducted, and medical records were reviewed to obtain information on medical and household exposures. Multivariable conditional logistic regression was used to derive odds ratio (OR) estimates of association between MRSA carriage and medical and household exposures.

RESULTS

In total, 117 cases and 119 controls were recruited to participate. Risk factors for MRSA carriage included having household members who took antibiotics or were hospitalized (OR: 3.27; 95% Confidence Interval (CI): 1.24-8.57) and prior hospitalization with a positive MRSA screen (OR: 3.21; 95% CI: 1.12-9.23). A lower proportion of cases than controls were previously hospitalized without a past positive MRSA screen (OR: 0.40; 95% CI: 0.19-0.87).

CONCLUSION

These findings suggest that household exposures are important determinants of MRSA nasal carriage in hospitalized patients screened at admission.

Panton-Valentine leukocidin producing Staphylococcus aureus nasal carriage, in North-Lebanon

OBJECTIVES

We investigated the prevalence and the risk factors of nasal carriage of Staphylococcus aureus carrying Panton-Valentine leukocidin genes [Sa PVL(+)] in pupils.

STUDY POPULATION AND METHODS

Two hundred and fifty-seven pupils were screened by nasal swabbing. The detection of 16S rRNA, mecA and luk-PV genes was performed by PCR and the risk factors were assessed with the statistical analysis of a questionnaire.

RESULTS

Thirty-one percent of pupils were colonized, with 16.4% of isolates carrying the luk-PV gene and 8.8% the mecA gene. Children aged 7years or more and living in a boarding school were the factors promoting nasal carriage 60% of children who presented with an abscess in the previous year were carriers of luk-PV gene Sa.

CONCLUSION

The study revealed a high prevalence of luk-PV gene among methicillin-susceptible strains and a statistically significant correlation between the presence of this gene and presenting with an abscess.

A systematic literature review and meta-analysis of factors associated with methicillin-resistant Staphylococcus aureus colonization at time of hospital or intensive care unit admission

OBJECTIVE

Screening for methicillin-resistant Staphylococcus aureus (MRSA) in high-risk patients is a legislative mandate in 9 US states and has been adopted by many hospitals. Definitions of high risk differ among hospitals and state laws. A systematic evaluation of factors associated with colonization is lacking. We performed a systematic review of the literature to assess factors associated with MRSA colonization at hospital admission.

DESIGN

We searched MEDLINE from 1966 to 2012 for articles comparing MRSA colonized and noncolonized patients on hospital or intensive care unit (ICU) admission. Data were extracted using a standardized instrument. Meta-analyses were performed to identify factors associated with MRSA colonization.

RESULTS

We reviewed 4,381 abstracts; 29 articles met inclusion criteria (n = 76,913 patients). MRSA colonization at hospital admission was associated with recent prior hospitalization (odds ratio [OR], 2.4 [95% confidence interval (CI), 1.3-4.7]; P < .01), nursing home exposure (OR, 3.8 [95% CI, 2.3-6.3]; P < .01), and history of exposure to healthcare-associated pathogens (MRSA carriage: OR, 8.0 [95% CI, 4.2-15.1]; Clostridium difficile infection: OR, 3.4 [95% CI, 2.2-5.3]; vancomycin-resistant Enterococci carriage: OR, 3.1 [95% CI, 2.5-4.0]; P < .01 for all). Select comorbidities were associated with MRSA colonization (congestive heart failure, diabetes, pulmonary disease, immunosuppression, and renal failure; P < .01 for all), while others were not (human immunodeficiency virus, cirrhosis, and malignancy). ICU admission was not associated with an increased risk of MRSA colonization (OR, 1.1 [95% CI, 0.6-1.8]; P = .87).

CONCLUSIONS

MRSA colonization on hospital admission was associated with healthcare contact, previous healthcare-associated pathogens, and select comorbid conditions. ICU admission was not associated with MRSA colonization, although this is commonly used in state mandates for MRSA screening. Infection prevention programs utilizing targeted MRSA screening may consider our results to define patients likely to have MRSA colonization.

Risk factors for development of methicillin-resistant Staphylococcus aureus infection among colonized patients

BACKGROUND

This study was conducted to identify clinical factors associated with development of infection caused by methicillin-resistant Staphylococcus aureus (MRSA) among hospitalized patients with nasal MRSA colonization.

METHODS

We conducted a prospective cohort with nested case-control study at a 672-bed, public, academic hospital in Dallas, Texas. The study duration was from January 1, 2008, to July 28, 2009. From the cohort of patients who had presence of nasal colonization with MRSA at admission, we identified patients who developed subsequent infection with MRSA during a 3-month period. We compared these patients (cases) with colonized patients who remained uninfected (controls; 2 controls per case). We collected demographic and clinical data and performed statistical analyses.

RESULTS

During the 19-month study period, 426 patients were found to have nasal colonization with MRSA. Of these, 36 (8.5%) developed a subsequent infection with MRSA within 3 months. When these 36 cases were compared with 72 controls, the factors independently associated with the development of subsequent infection were development of pressure ulcer during hospital stay (adjusted odds ratio, 5.82; 95% confidence interval: 2.21-15.31; P value=.000) and preadmission steroid therapy (adjusted odds ratio, 13.2; 95% confidence interval: 2.44-70.97; P value=.003).

CONCLUSION

History of steroid therapy prior to admission and development of pressure ulcer are associated with increased risk of subsequent MRSA infection in patients nasally colonized with MRSA.

Transmission of methicillin-resistant Staphylococcus aureus in the long term care facilities in Hong Kong

Background

The relative contribution of long term care facilities (LTCFs) and hospitals in the transmission of methicillin-resistant Staphylococcus aureus (MRSA) is unknown.

Methods

Concurrent MRSA screening and spa type analysis was performed in LTCFs and their network hospitals to estimate the rate of MRSA acquisition among residents during their stay in LTCFs and hospitals, by colonization pressure and MRSA transmission calculations.

Results

In 40 LTCFs, 436 (21.6%) of 2020 residents were identified as ‘MRSA-positive’. The incidence of MRSA transmission per 1000-colonization-days among the residents during their stay in LTCFs and hospitals were 309 and 113 respectively, while the colonization pressure in LTCFs and hospitals were 210 and 185 per 1000-patient-days respectively. MRSA spa type t1081 was the most commonly isolated linage in both LTCF residents (76/121, 62.8%) and hospitalized patients (51/87, 58.6%), while type t4677 was significantly associated with LTCF residents (24/121, 19.8%) compared with hospitalized patients (3/87, 3.4%) (p < 0.001). This suggested continuous transmission of MRSA t4677 among LTCF residents. Also, an inverse linear relationship between MRSA prevalence in LTCFs and the average living area per LTCF resident was observed (Pearson correlation −0.443, p = 0.004), with the odds of patients acquiring MRSA reduced by a factor of 0.90 for each 10 square feet increase in living area.

Conclusions

Our data suggest that MRSA transmission was more serious in LTCFs than in hospitals. Infection control should be focused on LTCFs in order to reduce the burden of MRSA carriers in healthcare settings.

Methicillin-resistant staphylococcus aureus nasal colonization prevalence among Emergency Medical Services personnel

INTRODUCTION

The prevalence of Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization among Emergency Medical Services (EMS) personnel is not well studied. Methicillin-resistant Staphylococcus aureus colonization can be a health hazard for both EMS personnel and patients. The aim of this study was to quantify the prevalence of MRSA colonization among EMS personnel. This study will help the scientific community understand the extent of this condition so that further protocols and policies can be developed to support the health and wellbeing of EMS personnel. Hypothesis/ Problem The hypothesis of this study was that the prevalence of MRSA colonization among EMS personnel is significantly higher than among the general population.

METHODS

This was a cross-sectional study. A total of 110 subjects were selected from two major US Mid-Atlantic fire departments. Methicillin-resistant Staphylococcus aureus colonization was detected by nasal swabbing. Nasal swabs were inoculated onto a special agar medium (C-MRSAgar) with polymerase chain reaction testing performed. One-sided binomial distribution at the Study Size 2.0 Web calculator was used. Using the Web calculator, p (H0 proportion) = 1.5%; a difference (H1-H0) 'Δ' = 4.53% can be detected at α = 5% and power = 80% with N = 110.

RESULTS

Samples were collected from 110 volunteers. Seven samples were positive for MRSA, resulting in a prevalence of 7/110 or 6.4% (95% CI, 1.8%-11%; P < .0003) compared with a 1.5% prevalence of MRSA colonization among the general population.

CONCLUSION

There is evidence that EMS personnel have a higher prevalence of MRSA colonization than the general population. This can be a risk to patients and can be recognized as an occupational hazard.

Trends and factors associated with initial and recurrent methicillin-resistant Staphylococcus aureus (MRSA) skin and soft-tissue infections among HIV-infected persons: an 18-year study

BACKGROUND

Factors associated with initial methicillin-resistant Staphylococcus aureus (MRSA) skin and soft-tissue infections (SSTIs) and their recurrence have not been fully elucidated among HIV-infected persons.

METHODS

We retrospectively evaluated a large cohort of HIV-infected patients from 1993 to 2010 for culture-proven MRSA SSTIs. Separate logistic regression models evaluated factors associated with initial and recurrent infections.

RESULTS

Of the 794 patients, 63 (8%) developed an initial infection (19.8 infections/1000 person years [PY]); risk factors included CD4 count <500 cells/mm(3) and HIV RNA level ≥400 copies/mL (P < .01), US Centers for Disease Control and Prevention (CDC) stage C versus A/B (P < .01), and injection drug use (IDU, P < .01). In all, 27% developed recurrence (206 infections/1000 PY); risk factors included hospital admission (P = .02). Minocycline for treatment of the initial infection was associated with an 80% decreased odds for recurrence (P = .03).

CONCLUSION

HIV control and avoidance of IDU may be useful in reducing rates of MRSA SSTIs among HIV-infected persons.

The importance of nursing homes in the spread of methicillin-resistant Staphylococcus aureus (MRSA) among hospitals

BACKGROUND

Hospital infection control strategies and programs may not consider control of methicillin-resistant Staphylococcus aureus (MRSA) in nursing homes in a county.

METHODS

Using our Regional Healthcare Ecosystem Analyst, we augmented our existing agent-based model of all hospitals in Orange County (OC), California, by adding all nursing homes and then simulated MRSA outbreaks in various health care facilities.

RESULTS

The addition of nursing homes substantially changed MRSA transmission dynamics throughout the county. The presence of nursing homes substantially potentiated the effects of hospital outbreaks on other hospitals, leading to an average 46.2% (range, 3.3%-156.1%) relative increase above and beyond the impact when only hospitals are included for an outbreak in OC's largest hospital. An outbreak in the largest hospital affected all other hospitals (average 2.1% relative prevalence increase) and the majority (~90%) of nursing homes (average 3.2% relative increase) after 6 months. An outbreak in the largest nursing home had effects on multiple OC hospitals, increasing MRSA prevalence in directly connected hospitals by an average 0.3% and in hospitals not directly connected through patient transfers by an average 0.1% after 6 months. A nursing home outbreak also had some effect on MRSA prevalence in other nursing homes.

CONCLUSIONS

Nursing homes, even those not connected by direct patient transfers, may be a vital component of a hospital's infection control strategy. To achieve effective control, a hospital may want to better understand how regional nursing homes and hospitals are connected through both direct and indirect (with intervening stays at home) patient sharing.

Patient-level factors associated with methicillin-resistant Staphylococcus aureus carriage at hospital admission: a systematic review

BACKGROUND

Selective methicillin-resistant Staphylococcus aureus (MRSA) screening programs target high-risk populations. To characterize high-risk populations, we conducted this systematic review to identify patient-level factors associated with MRSA carriage at hospital admission.

METHODS

Studies were identified in the MEDLINE (1950-2011) and EMBASE (1980-2011) databases. English studies were included if they examined adult populations and used multivariable analyses to examine patient-level factors associated with MRSA carriage at hospital admission. From each study, we abstracted details of the population, the risk factors examined, and the association between the risk factors and MRSA carriage at hospital admission.

RESULTS

Our electronic search identified 972 citations, from which we selected 27 studies meeting our inclusion criteria. The patient populations varied across the studies. Ten studies included all patients admitted to hospital, and the others were limited to specific hospital areas. MRSA detection methods also varied across studies. Ten studies obtained specimens from the nares only, whereas other studies also swabbed wounds, catheter sites, and the perianal region. Methods of MRSA diagnoses included polymerase chain reaction tests, cultures in various agar mediums, and latex agglutination tests. Patient age, gender, previous admission to hospital, and previous antibiotic use were the risk factors most commonly examined. The risk factor definition and study methods varied among studies to an extent that precluded meta-analysis.

CONCLUSION

The existing literature cannot be used to identify risk factors for MRSA colonization at the time of hospitalization. Future studies should be aware of the differences in the existing literature and aim to develop standardized risk factor definitions.

Prevalence dependent calibration of a predictive model for nasal carriage of methicillin-resistant Staphylococcus aureus

BACKGROUND

Published models predicting nasal colonization with Methicillin-resistant Staphylococcus aureus among hospital admissions predominantly focus on separation of carriers from non-carriers and are frequently evaluated using measures of discrimination. In contrast, accurate estimation of carriage probability, which may inform decisions regarding treatment and infection control, is rarely assessed. Furthermore, no published models adjust for MRSA prevalence.

METHODS

Using logistic regression, a scoring system (values from 0 to 200) predicting nasal carriage of MRSA was created using a derivation cohort of 3091 individuals admitted to a European tertiary referral center between July 2007 and March 2008. The expected positive predictive value of a rapid diagnostic test (GeneOhm, Becton & Dickinson Co.) was modeled using non-linear regression according to score. Models were validated on a second cohort from the same hospital consisting of 2043 patients admitted between August 2008 and January 2012. Our suggested correction score for prevalence was proportional to the log-transformed odds ratio between cohorts. Calibration before and after correction, i.e. accurate classification into arbitrary strata, was assessed with the Hosmer-Lemeshow-Test.

RESULTS

Treating culture as reference, the rapid diagnostic test had positive predictive values of 64.8% and 54.0% in derivation and internal validation corhorts with prevalences of 2.3% and 1.7%, respectively. In addition to low prevalence, low positive predictive values were due to high proportion (> 66%) of mecA-negative Staphylococcus aureus among false positive results. Age, nursing home residence, admission through the medical emergency department, and ICD-10-GM admission diagnoses starting with "A" or "J" were associated with MRSA carriage and were thus included in the scoring system, which showed good calibration in predicting probability of carriage and the rapid diagnostic test's expected positive predictive value. Calibration for both probability of carriage and expected positive predictive value in the internal validation cohort was improved by applying the correction score.

CONCLUSIONS

Given a set of patient parameters, the presented models accurately predict a) probability of nasal carriage of MRSA and b) a rapid diagnostic test's expected positive predictive value. While the former can inform decisions regarding empiric antibiotic treatment and infection control, the latter can influence choice of screening method.

Periprosthetic Joint Infection: What is on the Horizon?

Periprosthetic joint infection (PJI) will emerge as one of the most important issues for both orthopedic surgeons and researchers active in the field over the coming decades. Although the rate of PJI has not changed significantly over the past decade, the affected patients (hosts) being treated often present with more comorbidities than in the past, and the organisms responsible for these infections are evolving to become more difficult to treat. Fortunately, though, major strides in basic, translational, and clinical research have occurred in recent years that have armed the clinician with an armamentarium of techniques and technologies to better diagnose, prevent, and treat PJI. Advances in diagnostics, including refinements in established biomarkers, the introduction of point of service tests, developments in molecular techniques, and new techniques in advanced imaging will allow us to correctly identify the infecting pathogens and their virulence factors. Utilizing developed risk indexes to stratify and medically optimize our patients, modifying implants to incorporate antimicrobial and anti-biofilm properties, and developing clinically applicable vaccines and biofilm inhibiting enzymes will address our struggles in preventing PJI. Success of our future treatment strategies will hinge on refining the indications and technique of our current surgical procedures as well as the rational use of biofilm disrupting technologies and photodynamic therapy. Finally, the field of metabolomics, though still relatively in its infancy, likely holds the key to a novel diagnostic and treatment approach to infection and a more profound understanding of the pathophysiology of PJI on the human body.

Management of postoperative spinal infections

Postoperative surgical site infection (SSI) is a common complication after posterior lumbar spine surgery. This review details an approach to the prevention, diagnosis and treatment of SSIs. Factors contributing to the development of a SSI can be split into three categories: (1) microbiological factors; (2) factors related to the patient and their spinal pathology; and (3) factors relating to the surgical procedure. SSI is most commonly caused by Staphylococcus aureus. The virulence of the organism causing the SSI can affect its presentation. SSI can be prevented by careful adherence to aseptic technique, prophylactic antibiotics, avoiding myonecrosis by frequently releasing retractors and preoperatively optimizing modifiable patient factors. Increasing pain is commonly the only symptom of a SSI and can lead to a delay in diagnosis. C-reactive protein and magnetic resonance imaging can help establish the diagnosis. Treatment requires acquiring intra-operative cultures to guide future antibiotic therapy and surgical debridement of all necrotic tissue. A SSI can usually be adequately treated without removing spinal instrumentation. A multidisciplinary approach to SSIs is important. It is useful to involve an infectious disease specialist and use minimum serial bactericidal titers to enhance the effectiveness of antibiotic therapy. A plastic surgeon should also be involved in those cases of severe infection that require repeat debridement and delayed closure.

Prevalence of and risk factors for MRSA colonization in HIV-positive outpatients in Singapore

BACKGROUND

Whilst there have been studies on the risks and outcomes of MRSA colonization and infections in HIV-positive patients, local data is limited on the risk factors for MRSA colonization among these patients. We undertook this study in a tertiary HIV care centre to document the risk factors for colonization and to determine the prevalence of MRSA colonization among HIV-positive outpatients in Singapore.

METHODS

This was a cross-sectional study in which factors associated with MRSA positivity among patients with HIV infection were evaluated. A set of standardized questionnaire and data collection forms were available to interview all recruited patients. Following the interview, trained nurses collected swabs from the anterior nares/axilla/groin (NAG), throat and peri-anal regions. Information on demographics, clinical history, laboratory results and hospitalization history were retrieved from medical records.

RESULTS

MRSA was detected in swab cultures from at least 1 site in 15 patients (5.1%). Inclusion of throat and/or peri-anal swabs increased the sensitivity of NAG screening by 20%. Predictors for MRSA colonization among HIV-positive patients were age, history of pneumonia, lymphoma, presence of a percutaneous device within the past 12 months, history of household members hospitalized more than two times within the past 12 months, and a most recent CD4 count less than 200.

CONCLUSIONS

This study highlights that a proportion of MRSA carriers would have been undetected without multiple-site screening cultures. This study could shed insight into identifying patients at risk of MRSA colonization upon hospital visit and this may suggest that a risk factor-based approach for MRSA surveillance focusing on high risk populations could be considered.

The prevalence of methicillin-resistant staphylococcus aureus among out-of-hospital care providers and emergency medical technician students

OBJECTIVE

We compared the methicillin-resistant Staphylococcus aureus (MRSA) carrier rate among out-of-hospital care providers with greater than six months' experience in emergency medical services (EMS) care with that of emergency medical technician (EMT) students with two months or less of observation time as part of their clinical training.

METHODS

We conducted a prospective study utilizing a convenience sample of out-of-hospital care providers and EMT students in an urban EMS system operating in the Midwest during October and November 2006. One hundred thirty-four out-of-hospital care providers and 152 EMT students were tested for MRSA susceptibility using the cefoxitin disk diffusion method.

RESULTS

Contrary to our hypothesis, we did not find a statistically significant difference in MRSA nasal colonization between out-of-hospital care providers (4.5%; 95% confidence interval [CI] 1.0, 8.0) and EMT students (5.3%; 95% CI 1.7, 8.8). A subgroup analysis showed that among out-of-hospital care providers, paramedics had a higher rate of nasal colonization than EMTs (5.6% vs. 2.2%).

CONCLUSION

We found that out-of-hospital care providers and EMT students had higher nasal colonization rates than the reported rate for the U.S. population (0.084% at the time the study was conducted and 1.5% currently). It is imperative that both groups adhere to infection control practices.

Prevalence and risk factors for methicillin-resistant Staphylococcus aureus colonization in a diabetic outpatient population: a prospective cohort study

BACKGROUND

Diabetes mellitus is a risk factor for methicillin-resistant Staphylococcus aureus (MRSA) colonization and infection. We attempted to determine the prevalence and risk factors for MRSA colonization in a population of outpatients with diabetes.

METHODS

This prospective cohort study enrolled patients with diabetes. Anterior nares cultures were obtained from patients with diabetes admitted to outpatient endocrinology and metabolism clinics, and risk factors for MRSA colonization were analyzed.

RESULTS

Out of the 304 patients evaluated, 127 (41.9%) were colonized with S aureus and 30 (9.9%) were colonized with MRSA. Overall, 23.6% of all S aureus isolates were MRSA. In multivariate analysis, factors independently associated with an increased risk of MRSA colonization included the presence of connective tissue disease (odds ratio, 7.075; 95% confidence interval, 2.157-23.209; P = .001) and insulin therapy (odds ratio, 3.910; 95% confidence interval, 1.652-9.251; P = .002).

CONCLUSIONS

The prevalence of MRSA colonization in our sample of diabetic outpatients was 9.9%. Independent risk factors for MRSA colonization were the presence of connective tissue disease and insulin use. A better understanding of the epidemiology and risk factors for nasal MRSA colonization in the persons with diabetes may have significant implications for the treatment and prevention of MRSA infections.

Evaluation of the sensitivity and specificity of criteria for isolation of patients admitted to a specialized cancer hospital

Early isolation of patients possibly colonized by multi-resistant microorganisms can minimize their spread, reducing cases of hospital infection and the related costs. This study aimed to identify the sensitivity and specificity of the criteria for isolation of patients admitted to a specialized cancer hospital. Cross-sectional study with a population of 61 patients coming from other hospitals who were admitted to the hospital between March 1st and August 31th, 2009. At the moment of admission, a data collection instrument was filled out and nasal and anal swabs were collected for microbiological culture. Of the 56 patients who met the isolation criteria, 30 (49.2%) presented positive cultures for multi-resistant microorganisms and methicillin-resistant Staphylococcus aureus was the most frequently identified microorganism. Most patients colonized by multi-resistant microorganisms were isolated at the moment of admission. The sensitivity of the isolation criteria was 90% and the specificity was 6.5%.

Risk factors for nasal carriage of methicillin-resistant Staphylococcus aureus among patients with end-stage renal disease in Taiwan

BACKGROUND/PURPOSE

Patients with end-stage renal disease (ESRD) are at particular risk for methicillin-resistant Staphylococcus aureus (MRSA) infections, especially via nasal colonization of MRSA. Surveillance cultures are recommended to identify patients colonized by MRSA.

METHODS

Clinical data and screening cultures of S. aureus from the anterior nares of 541 patients on long-term dialysis in the hospitals were performed in March 2007. The follow-up survey was conducted 1 year later.

RESULTS

A total of 32 (5.9%) of the 541 patients were positive nasal cultures for MRSA, while 89 (16.5%) were positive for methicillin-susceptible S. aureus (MSSA). In a multivariate analysis, risk factors for ESRD patients with MRSA colonization included congestive heart failure, nursing home admission, and nasogastric tube feeding in the last 3 months. Follow-up of the 32 MRSA colonized patients showed that one (3.1%) died due to MSSA and three (9.3%) died due from MRSA infection.

CONCLUSIONS

We found that patients with ESRD and MRSA nasal colonization were associated with a history of congestive heart failure, nursing home admission, and nasogastric tube feeding in the last 3 months.

Predictive Risk Factors for Methicillin-Resistant Staphylococcus aureus (MRSA) Colonisation among Adults in Acute Care Settings: A Systematic Review

BACKGROUND

Asymptomatically colonised MRSA carriers serve as a substantial reservoir for person-to-person transmission of MRSA in the acute care setting. Although many studies have evaluated prognostic risk factors for MRSA colonisation on patient admission to an acute care setting, a comprehensive review of all the prognostic risk factors was not identified in a preliminary search of the literature.

OBJECTIVES

A systematic review was performed to identify and evaluate the association between risk factors and MRSA colonisation.

INCLUSION CRITERIA

Studies that included all adult patients on admission in acute care settings were considered in this review.All independent risk factors of MRSA colonisation were analysed in this review.Cohort and case-control studies are main designs associated identifying the independent risk factors for MRSA colonisation.The primary outcome of interest was presence and absence of MRSA on admission, and then independent risk factors associated with MRSA colonisation on admission were identified.

SEARCH STRATEGY

MEDLINE, EMABSE, and CINAHL databases were searched for prognostic studies published between 1990 and 2010 that examined the association between risk factors and MRSA colonisation. The search included both published and unpublished studies written in the English language.

METHODOLOGICAL QUALITY

Included studies were assessed using a standardised critical appraisal instrument that was developed for prognostic studies in infection control field.

DATA COLLECTION

Data were collected from included papers in the review using the standardised data extraction tool from the JBI SUMARI Program; and the data extraction form was modified based on the characteristics of prognostic studies for infection control.

DATA SYNTHESIS

All risk factors in included studies were aggregated depending on their clinical characteristics. Data of any aggregated factors was pooled into meta-analysis based on univariate estimates and multivariate estimates separately when more than two groups of data in selected studies were available.

RESULTS

Fifteen prospective studies, including a total 16,467 patients, were eligible for inclusion in the meta-analyses. More than 30 independent risk factors were identified and aggregated. The risk factors associated with MRSA colonisation in the meta-analyses include hospitalisation within the last 24 months, previous admission to a long-term care facility (LTCF) or a rehabilitation facility within the last 18 months, antibiotic use within the past 12 months, the presence of skin lesion, surgical intervention within the last 60 months, indwelling urinary catheter, intensive care unit (ICU) admission in the last 5 years, previous MRSA colonisation, intra-hospital transfer, male sex, comorbidity of chronic health evaluation class C or D, and the presence of fatal illness.

CONCLUSIONS

The identification of risk factors for MRSA colonisation on admission may contribute to improved effectiveness and efficiency of current MRSA prevention strategies and control MRSA spread and acquisition in acute care settings. The outcomes of this review may facilitate prediction model development to quickly identify potential MRSA carriers before admission.

Screening for methicillin-resistant Staphylococcus aureus (MRSA) in community-recruited injection drug users: are throat swabs necessary?

We examined and described colonization of MRSA in the anterior nares and throat from 184 community-recruited injection drug users. Thirty-seven (20%) were positive for MRSA: most (34, 92%) were carriers in the nares; while only three (8%) were carriers detected by throat swabs alone. The majority (29, 78%) of MRSA isolates were PVL positive.

Innate and adaptive immune responses against Staphylococcus aureus skin infections

Staphylococcus aureus is an important human pathogen that is responsible for the vast majority of bacterial skin and soft tissue infections in humans. S. aureus can also become more invasive and cause life-threatening infections such as bacteremia, pneumonia, abscesses of various organs, meningitis, osteomyelitis, endocarditis, and sepsis. These infections represent a major public health threat due to the enormous numbers of these infections and the widespread emergence of methicillin-resistant S. aureus (MRSA) strains. MSRA is endemic in hospitals worldwide and is rapidly spreading throughout the normal human population in the community. The increasing frequency of MRSA infections has complicated treatment as these strains are more virulent and are increasingly becoming resistant to multiple different classes of antibiotics. The important role of the immune response against S. aureus infections cannot be overemphasized as humans with certain genetic and acquired immunodeficiency disorders are at an increased risk for infection. Understanding the cutaneous immune responses against S. aureus is essential as most of these infections occur or originate from a site of infection or colonization of the skin and mucosa. This review will summarize the innate immune responses against S. aureus skin infections, including antimicrobial peptides that have direct antimicrobial activity against S. aureus as well as pattern recognition receptors and proinflammatory cytokines that promote neutrophil abscess formation in the skin, which is required for bacterial clearance. Finally, we will discuss the recent discoveries involving IL-17-mediated responses, which provide a key link between cutaneous innate and adaptive immune responses against S. aureus skin infections.

Risk factors for household transmission of community-associated methicillin-resistant Staphylococcus aureus

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a community pathogen. Community-associated (CA) MRSA infections have occurred among multiple members of a household. We describe the incidence of and risk factors for MRSA colonization among household contacts of children with CA-MRSA infections.

METHODS

MRSA-infected children <18 years of age who lacked established healthcare-associated MRSA risk factors were identified through surveillance at 12 Minnesota hospital laboratories. Nasal swab specimens and information on medical history and hygiene behaviors were collected from case-patients and enrolled household contacts during home visits. S. aureus isolates obtained from nasal cultures were screened for oxacillin resistance.

RESULTS

In all, 236 households consisting of 236 case-patients and 712 household contacts were enrolled. Home visits were conducted on an average of 69 days after the onset of symptom in case-patients (range: 16-178 days). Twenty-nine (13%) case-patients and 82 (12%) household contacts had MRSA nasal colonization. Nasal MRSA colonization in ≥ 1 household contact occurred in 58 (25%) households. Household contacts who assisted the case-patient to bathe or who shared balms/ointments/lotion with the case-patient were more likely to be colonized (P < 0.01, P < 0.05), whereas those who reported using antibacterial versus nonantibacterial soap for hand washing were less likely to be colonized (P < 0.05) with MRSA clonally related to the case-patient infection isolate.

CONCLUSIONS

Only 13% of case-patients had MRSA nasal colonization on an average of 69 days after their initial MRSA infection. CA-MRSA colonization may be short-lived or may occur at non-nasal sites. One quarter of households had at least one household contact colonized with MRSA. Modifiable behaviors, such as sharing personal items, may contribute to transmission.

Association of methicillin-resistant Staphylococcus aureus (MRSA) colonization with high-risk sexual behaviors in persons infected with human immunodeficiency virus (HIV)

Methicillin-resistant Staphylococcus aureus (MRSA) infections are an important cause of morbidity, especially among human immunodeficiency virus (HIV)-infected persons. Since an increasing number of MRSA skin and soft tissue infections involve the perigenital areas, some have suggested that these infections may be sexually transmitted. We performed a cross-sectional study among HIV-infected adults from 4 geographically diverse United States military HIV clinics to determine the prevalence of and the factors (including sexual practices) associated with MRSA colonization. Swabs were collected from the nares, throat, axillae, groin area, and perirectal area for S. aureus colonization. Data on sociodemographic characteristics, medical conditions, and sexual history were collected. Multivariate logistic regression models evaluated factors associated with carriage. We studied 550 HIV-infected adults with a median age of 42 years; 93% were male; and race/ethnicity was white for 46%, African American for 35%, and other for 19%. Median CD4 count was 529 cells/mm, 11% had a history of a MRSA infection, and 21% had a sexually transmitted infection within the last year, including 8% with syphilis. One hundred eighty (33%) were colonized with S. aureus and 22 (4%) with MRSA. The most common location for carriage was the nares, followed by the perigenital area (groin or perirectal area). Factors associated with MRSA carriage in the multivariate analyses included a sexually transmitted infection in the last year (odds ratio [OR], 4.2; p<0.01), history of MRSA infection (OR, 9.4; p<0.01), and African American compared with white race/ethnicity (OR, 3.5; p=0.01). In separate multivariate models, syphilis, nongonococcal urethritis, and public bath use were also associated with MRSA carriage (all p<0.01). In conclusion, a history of recent sexually transmitted infections, including syphilis and urethritis, was associated with MRSA carriage. These data suggest that high-risk sexual activities may play a role in MRSA transmission.

Evaluation of the impact of direct plating, broth enrichment, and specimen source on recovery and diversity of methicillin-resistant Staphylococcus aureus isolates among HIV-infected outpatients

We compared recovery of Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) from nasal and groin swab specimens of 600 HIV-infected outpatients by selective and nonselective direct plating and broth enrichment. Swabs were collected at baseline, 6-month, and 12-month visits and cultured by direct plating to mannitol salt agar (MSA) and CHROMagar MRSA (CM) and overnight broth enrichment with subculture to MSA (broth). MRSA isolates were characterized by pulsed-field gel electrophoresis (PFGE), staphylococcal cassette chromosome mec (SCCmec) typing, and PCR for the Panton-Valentine leukocidin. At each visit, 13 to 15% of patients were colonized with MRSA and 30 to 33% were colonized with methicillin-susceptible S. aureus (MSSA). Broth, CM, and MSA detected 95%, 82%, and 76% of MRSA-positive specimens, respectively. MRSA recovery was significantly higher from broth than CM (P ≤ 0.001) or MSA (P ≤ 0.001); there was no significant difference in recovery between MSA and CM. MSSA recovery also increased significantly when using broth than when using MSA (P ≤ 0.001). Among specimens collected from the groin, broth, CM, and MSA detected 88%, 54%, and 49% of the MRSA-positive isolates, respectively. Broth enrichment had a greater impact on recovery of MRSA from the groin than from the nose compared to both CM (P ≤ 0.001) and MSA (P ≤ 0.001). Overall, 19% of MRSA-colonized patients would have been missed with nasal swab specimen culture only. USA500/Iberian and USA300 were the most common MRSA strains recovered, and USA300 was more likely than other strain types to be recovered from the groin than from the nose (P = 0.05).

Does trimethoprim-sulfamethoxazole prophylaxis for HIV induce bacterial resistance to other antibiotic classes? Results of a systematic review

BACKGROUND

Trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis has long been recommended for immunosuppressed HIV-infected adults and children born to HIV-infected women. Despite this, many resource-limited countries have not implemented this recommendation, partly because of fear of widespread antimicrobial resistance not only to TMP-SMX, but also to other antibiotics. We aimed to determine whether TMP-SMX prophylaxis in HIV-infected and/or exposed individuals increases bacterial resistance to antibiotics other than TMP-SMX.

METHODS

A literature search was conducted in Medline, Global Health, Embase, Web of Science, ELDIS, and ID21.

RESULTS

A total of 501 studies were identified, and 17 met the inclusion criteria. Only 8 studies were of high quality, of which only 2 had been specifically designed to answer this question. Studies were classified as (1) studies in which all participants were infected and/or colonized and in which rates of bacterial resistance were compared between those taking or not taking TMP-SMX and (2) studies comparing those who had a resistant infection with those who were not infected. Type 1 studies showed weak evidence that TMP-SMX protects against resistance. Type 2 studies provided more convincing evidence that TMP-SMX protects against infection.

CONCLUSION

There was some evidence that TMP-SMX prophylaxis protects against resistance to other antibiotics. However, more carefully designed studies are needed to answer the question conclusively.

The role of prophylactic antibiotics in open fractures in an era of community-acquired methicillin-resistant Staphylococcus aureus

Infection is a feared complication and a common cause of loss of function following open fractures. Despite the evidence supporting the administration of prophylactic antibiotics after open fractures, data demonstrating the optimal regimen is lacking. We reviewed the data supporting the current prophylaxis recommendations and the changing epidemiology of Staphylococcus aureus, the most common cause of surgical site infection in patients with open fractures. Although widespread emergence of methicillin-resistant Staphylococcus aureus (MRSA) has been described in both hospital and community settings, to date, no studies have addressed the need for prophylaxis against MRSA in patients with open fractures. Until well-designed randomized trials are conducted, we recommend that providers consider selecting antibiotics active against MRSA for open fracture prophylaxis based on the local prevalence of MRSA carriage and individualized risk factors.

Revisiting Methicillin-Resistant Staphylococcus aureus Infections

Within less than 50 years, methicillin-resistant Staphylococcus aureus (MRSA) made a tremendous impact worldwide. It is not limited to medical facilities and healthcare institutions anymore. Indeed since two decades, cases of MRSA infections arising from the community among apparently healthy individuals are increasing. In this paper, I will present a case of community-associated MRSA sepsis followed by a comprehensive review about the history, pathogenesis, epidemiology, clinical presentations, diagnostic modalities, therapeutic options, contributing factors, growing cost and other pertinent elements of this newly evolving epidemic of MRSA infections.

Optimizing delivery of care for patients with MRSA infection: focus on transitions of care

Staphylococcus aureus is among the most prevalent pathogens isolated from hospitalized patients; those infected with methicillin-resistant strains have longer hospital stays and higher total costs compared with those infected by methicillin-susceptible strains. A multidisciplinary team of health care providers, including hospitalists and other hospital-based physicians, clinical pharmacists, infectious disease specialists, infection control professionals, and case managers, is key to improving treatment and outcomes in these patients. Optimizing transitions of care for hospitalized patients with S aureus infections can improve quality and reduce total costs of care. Hospital length of stay can be shortened by initiating timely, appropriate empiric therapy and by transitioning suitable patients to outpatient antimicrobial therapy. The number of hospitalizations can be reduced by identifying patients who are suitable candidates for initial outpatient antimicrobial therapy. Consistent with good antimicrobial stewardship, the risk of resistance can be minimized by de-escalating empiric therapy to a more narrow-spectrum agent once culture and susceptibility testing results are known. There are several antimicrobial agents available for the management of S aureus infections, including methicillin-resistant S aureus. Consideration of these agents' characteristics may facilitate optimal transition of patients through health care settings.

National athletic trainers' association position statement: skin diseases

OBJECTIVE

To present recommendations for the prevention, education, and management of skin infections in athletes.

BACKGROUND

Trauma, environmental factors, and infectious agents act together to continually attack the integrity of the skin. Close quarters combined with general poor hygiene practices make athletes particularly vulnerable to contracting skin diseases. An understanding of basic prophylactic measures, clinical features, and swift management of common skin diseases is essential for certified athletic trainers to aid in preventing the spread of infectious agents.

RECOMMENDATIONS

These guidelines are intended to provide relevant information on skin infections and to give specific recommendations for certified athletic trainers and others participating in athletic health care.

Recurrent community-acquired methicillin-resistant Staphylococcus aureus infections in an HIV-infected person

HIV-infected persons are at heightened risk for recurrent community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, but there are limited data regarding the molecular characterization of these events. We describe an HIV-infected patient with 24 soft tissue infections and multiple colonization events. Molecular genotyping from 33 nonduplicate isolates showed all strains were USA300, Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME) positive, and genetically related.

Prevalence, persistence, and microbiology of Staphylococcus aureus nasal carriage among hemodialysis outpatients at a major New York Hospital

The study aimed to determine the natural history of Staphylococcus aureus nasal colonization in hemodialysis outpatients. Surveillance cultures were taken from patients presenting for hemodialysis or routine care to identify S. aureus nasal carriers. A prospective cohort study was performed to identify risks for persistent colonization. Detailed microbiologic and molecular studies of colonizing isolates were performed. Only 23/145 (15.9%) dialysis patients were persistently colonized, and only HIV-positive status was associated with persistence (P = 0.05). Prior hospitalization was the only risk factor for methicillin-resistant S. aureus carriage (OR 2.5, P = 0.03). In isolates from patients with ≤ 42 days of vancomycin exposure, vancomycin minimum bactericidal concentrations (MBCs) increased with duration of exposure. Among dialysis patients, S. aureus colonization was limited and transient; only HIV status was associated with persistence. Nevertheless, duration of vancomycin exposure was associated with increasing vancomycin MBCs. Vancomycin exposure in S. aureus carriers may be involved in increasing resistance.