Carriage of methicillin-resistant Staphylococcus aureus at hospital admission

Prevalence of methicillin-resistant Staphylococcus aureus carriage on admission among patients attending regional hospitals in Dar es Salaam, Tanzania

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for hospital and community acquired infection. Colonization with MRSA is associated with a high risk of developing infection. This study aimed to determine the rate of MRSA carriage on admission and the associated risk factors among patients attending regional hospitals, in Dar es Salaam, Tanzania.

Results

A total of 258 patients were included in this study. Nasal swabs were collected on admission to the hospital and after 48 h of hospital stay for detection of MRSA. Of 258 patients enrolled, 89 (34.5%) were colonized with S. aureus and out them 22 (24.7%) were carriers of MRSA, giving an overall MRSA nasal carriage rate of 8.5% (22/258). One patient acquired MRSA while admitted in the hospital. Most of the S. aureus isolates 85 (95.5%) were resistant to penicillin. Resistance to gentamycin, ciprofloxacin, kanamycin, linezolid and mupirocin were 14.6, 11.2, 11.2, 3.4 and 1.1%, respectively. The prevalence of inducible clindamycin resistance, constitutive clindamycin resistance, MS phenotype (resistance to erythromycin alone), and multidrug resistance was 21.3, 3.4, 12.4, and 16.9%, respectively. We observed a statistically significant association between MRSA and multiple drugs resistance among S. aureus isolates (p = 0.001). Of the risk factors investigated none were statistically significant associated with MRSA.

Conclusion

There is a high prevalence of MRSA among patients on admission at the two municipal hospitals in Dar es Salaam. The high prevalence of MRSA and the increased rates of resistance to commonly used antimicrobials among MRSA isolates call for attention to the importance of including the screening of MRSA in our hospitals setting in order to prevent further spread of MRSA strains to other patients and to the communities. Control and prevention strategies should be emphasized including decolonization.

Infection Control in Alternative Health Care Settings: An Update

With changing health care delivery, patients receive care at various settings including acute care hospitals, nursing homes, outpatient primary care and specialty clinics, and at home, exposing them to pathogens in various settings. Various health care settings face unique challenges, requiring individualized infection control programs. Infection control programs in nursing homes should address surveillance for infections and antimicrobial resistance, outbreak investigation and control plan for epidemics, isolation precautions, hand hygiene, staff education, and employee and resident health programs.

Gloves, gowns and masks for reducing the transmission of meticillin-resistant Staphylococcus aureus (MRSA) in the hospital setting

BACKGROUND

Meticillin-resistant Staphylococcus aureus (MRSA; also known as methicillin-resistant S aureus) is a common hospital-acquired pathogen that increases morbidity, mortality, and healthcare costs. Its control continues to be an unresolved issue in many hospitals worldwide. The evidence base for the effects of the use of gloves, gowns or masks as control measures for MRSA is unclear.

OBJECTIVES

To assess the effectiveness of wearing gloves, a gown or a mask when contact is anticipated with a hospitalised patient colonised or infected with MRSA, or with the patient's immediate environment.

SEARCH METHODS

We searched the Specialised Registers of three Cochrane Groups (Wounds Group on 5 June 2015; Effective Practice and Organisation of Care (EPOC) Group on 9 July 2013; and Infectious Diseases Group on 5 January 2009); CENTRAL (The Cochrane Library 2015, Issue 6); DARE, HTA, NHS EED, and the Methodology Register (The Cochrane Library 2015, Issue 6); MEDLINE and MEDLINE In-Process & Other Non-Indexed Citations (1946 to June week 1 2015); EMBASE (1974 to 4 June 2015); Web of Science (WOS) Core Collection (from inception to 7 June 2015); CINAHL (1982 to 5 June 2015); British Nursing Index (1985 to 6 July 2010); and ProQuest Dissertations & Theses Database (1639 to 11 June 2015). We also searched three trials registers (on 6 June 2015), references list of articles, and conference proceedings. We finally contacted relevant individuals for additional studies.

SELECTION CRITERIA

Studies assessing the effects on MRSA transmission of the use of gloves, gowns or masks by any person in the hospital setting when contact is anticipated with a hospitalised patient colonised or infected with MRSA, or with the patient's immediate environment. We did not assess adverse effects or economic issues associated with these interventions.We considered any comparator to be eligible. With regard to study design, only randomised controlled trials (clustered or not) and the following non-randomised experimental studies were eligible: quasi-randomised controlled trials (clustered or not), non-randomised controlled trials (clustered or not), controlled before-and-after studies, controlled cohort before-after studies, interrupted time series studies (controlled or not), and repeated measures studies. We did not exclude any study on the basis of language or date of publication.

DATA COLLECTION AND ANALYSIS

Two review authors independently decided on eligibility of the studies. Had any study having been included, two review authors would have extracted data (at least for outcome data) and assessed the risk of bias independently. We would have followed the standard methodological procedures suggested by Cochrane and the Cochrane EPOC Group for assessing risk of bias and analysing the data.

MAIN RESULTS

We identified no eligible studies for this review, either completed or ongoing.

AUTHORS' CONCLUSIONS

We found no studies assessing the effects of wearing gloves, gowns or masks for contact with MRSA hospitalised patients, or with their immediate environment, on the transmission of MRSA to patients, hospital staff, patients' caregivers or visitors. This absence of evidence should not be interpreted as evidence of no effect for these interventions. The effects of gloves, gowns and masks in these circumstances have yet to be determined by rigorous experimental studies, such as cluster-randomised trials involving multiple wards or hospitals, or interrupted time series studies.

Colonization with Multi-Drug Resistant Organisms in Nursing Homes: Scope, Importance, and Management

Bacterial infections are among the most common causes of morbidity and mortality in Nursing Homes (NH) and other long term care facilities. Multi-drug resistant organisms (MDROs) represent an ever-increasing share of causative agents of infection, and their prevalence in NHs is now just as high as in acute-care facilities, or even higher. Indeed, NHs are now considered a major reservoir of MDROs for the community at large. Asymptomatic colonization is usually a prerequisite to development of symptomatic infection. While progress has been made in defining epidemiology of MDROs in NHs, few studies have evaluated the role of changing healthcare delivery in introducing and further transmitting MDROs in this setting. Furthermore, the factors influencing the spread of colonization and the key prognostic indicators leading to symptomatic infections in the burgeoning short stay population need to be explored further. The difficulty of this task lies in the heterogeneity of NHs in terms of focus of care, organization and resources, and on the diversity among the many MDRO species encountered, which harbor different resistance genes and with a different prevalence depending on the geographic location, local antimicrobial pressure and residents risk factors such as use of indwelling devices, functional disability, wounds and other comorbidities. We present literature findings on the scope and importance of colonization as a pathway to infection with MDROs in NHs, underline important open questions that need further research, and discuss the strength of the evidence for current and proposed screening, prevention, and management interventions.

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.

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.

Quantifying the impact of extranasal testing of body sites for methicillin-resistant Staphylococcus aureus colonization at the time of hospital or intensive care unit admission

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of healthcare-associated infections. Recent legislative mandates require nares screening for MRSA at hospital and intensive care unit (ICU) admission in many states. However, MRSA colonization at extranasal sites is increasingly recognized. We conducted a systematic review of the literature to identify the yield of extranasal testing for MRSA.

DESIGN

We searched MEDLINE from January 1966 through January 2012 for articles comparing nasal and extranasal screening for MRSA colonization. Studies were categorized by population tested, specifically those admitted to ICUs and those admitted to hospitals with a high prevalence (6% or greater) or low prevalence (less than 6%) of MRSA carriers. Data were extracted using a standardized instrument.

RESULTS

We reviewed 4,381 abstracts and 735 articles. Twenty-three articles met the criteria for analysis ((n = 39,479 patients). Extranasal MRSA screening increased the yield by approximately one-third over nares alone. The yield was similar at ICU admission (weighted average, 33%; range, 9%-69%) and hospital admission in high-prevalence (weighted average, 37%; range, 9%-86%) and low-prevalence (weighted average, 50%; range, 0%-150%) populations. For comparisons between individual extranasal sites, testing the oropharynx increased MRSA detection by 21% over nares alone; rectum, by 20%; wounds, by 17%; and axilla, by 7%.

CONCLUSIONS

Extranasal MRSA screening at hospital or ICU admission in adults will increase MRSA detection by one-third compared with nares screening alone. Findings were consistent among subpopulations examined. Extranasal testing may be a valuable strategy for outbreak control or in settings of persistent disease, particularly when combined with decolonization or enhanced infection prevention protocols.

Staphylococcus aureus adherence to Candida albicans hyphae is mediated by the hyphal adhesin Als3p

The bacterium Staphylococcus (St.) aureus and the opportunistic fungus Candida albicans are currently among the leading nosocomial pathogens, often co-infecting critically ill patients, with high morbidity and mortality. Previous investigations have demonstrated preferential adherence of St. aureus to C. albicans hyphae during mixed biofilm growth. In this study, we aimed to characterize the mechanism behind this observed interaction. C. albicans adhesin-deficient mutant strains were screened by microscopy to identify the specific receptor on C. albicans hyphae recognized by St. aureus. Furthermore, an immunoassay was developed to validate and quantify staphylococcal binding to fungal biofilms. The findings from these experiments implicated the C. albicans adhesin agglutinin-like sequence 3 (Als3p) in playing a major role in the adherence process. This association was quantitatively established using atomic force microscopy, in which the adhesion force between single cells of the two species was significantly reduced for a C. albicans mutant strain lacking als3. Confocal microscopy further confirmed these observations, as St. aureus overlaid with a purified recombinant Als3 N-terminal domain fragment (rAls3p) exhibited robust binding. Importantly, a strain of Saccharomyces cerevisiae heterologously expressing Als3p was utilized to further confirm this adhesin as a receptor for St. aureus. Although the parental strain does not bind bacteria, expression of Als3p on the cell surface conferred upon the yeast the ability to strongly bind St. aureus. To elucidate the implications of these in vitro findings in a clinically relevant setting, an ex vivo murine model of co-infection was designed using murine tongue explants. Fluorescent microscopic images revealed extensive hyphal penetration of the epithelium typical of C. albicans mucosal infection. Interestingly, St. aureus bacterial cells were only seen within the epithelial tissue when associated with the invasive hyphae. This differed from tongues infected with St. aureus alone or in conjunction with the als3 mutant strain of C. albicans, where bacterial presence was limited to the outer layers of the oral tissue. Collectively, the findings generated from this study identified a key role for C. albicans Als3p in mediating this clinically relevant fungal-bacterial interaction.

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.

Universal methicillin-resistant Staphylococcus aureus (MRSA) surveillance for adults at hospital admission: an economic model and analysis

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The role of colonization pressure in nosocomial transmission of methicillin-resistant Staphylococcus aureus

BACKGROUND

Colonized or infected patients are a major reservoir for patient-to-patient transmission of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals. Despite attempted adherence to recommended infection prevention and control procedures, a general medicine unit in our hospital continued to experience ongoing transmission of MRSA. The role that colonization pressure (CP) plays in nosocomial transmission of MRSA on a general medicine unit was assessed, and a threshold CP above which additional IP&C practices should be implemented was proposed.

METHODS

From January 2005 to December 2006, all patients admitted to a 36-bed general medicine unit were screened on admission for MRSA. Monthly MRSA nosocomial incidence (new nosocomial cases x 1000/susceptible patient-days) and CP (number of MRSA patient-days x 100/total patient-days) were calculated. The relative risk (RR) of MRSA transmission above and below the median CP with 95% confidence interval was calculated.

RESULTS

Twenty-one cases of nosocomially acquired MRSA were detected during the study period, with transmission occurring in 8 separate months. The median CP during the 2 years was 6.7%. The RR of MRSA acquisition increased as CP increased above the median (RR, 7.6; 95% CI: 1.1-52.6; P = .008). MRSA outbreaks were declared on 2 separate occasions, and, in each, the CP for the preceding month was greater than the median value of 6.7%.

CONCLUSION

CP has a significant effect on the subsequent transmission of MRSA on a general medicine unit. Ongoing monitoring of CP provides the opportunity for early implementation of enhanced infection prevention and control practices and can potentially decrease nosocomial transmission of MRSA and prevent outbreaks.

The prevalence of methicillin resistant Staphylococus aureus in orthopaedics in a non-selective screening policy

BACKGROUND

The aim of this study was to assess the true incidence and prevalence of MRSA colonisation and infection in the elective and trauma orthopaedic population in Rotherham District General Hospital.

MATERIALS AND METHODS

This prospective study non-selectively screened 690 consecutive trauma and elective orthopaedic patients over three months in 2005.

RESULTS

Of these, 27 were positive for either colonisation or wound infection with MRSA. Of those, 13 were previously known to have been colonised with MRSA and the 14 others were unexpectedly either colonised or subsequently developed wound infections. The new cases would not have been identified using any current selective screening protocol, as they did not fall into a high-risk category. Many were young, had no co-morbidities and no contact with hospitals in the past. Our study seems to indicate that selective screening will miss a significant number of cases.

CONCLUSION

We conclude that MRSA screening for all orthopaedic patients is needed when admitted to hospital, as colonisation is no longer confined to what has been previously identified as high-risk groups. The consequences of a subsequent MRSA infection have significant implications, socially, financially and clinically.

Financial implications of plans to combat methicillin-resistant Staphylococcus aureus (MRSA) in an orthopaedic department

INTRODUCTION

The aim of this study was to calculate retrospectively the cost of MRSA infections in the elective and trauma orthopaedic population in Rotherham District General Hospital in a 3-month period during 2005.

PATIENTS AND METHODS

A total of 686 patients were admitted to the orthopaedic wards and the surgical wounds 10 patients became infected with MRSA.

RESULTS

The cost of these infections when extrapolated over 12 months was pound384,000 excluding staff costs.

CONCLUSIONS

The key in the fight against MRSA in the hospital setting is multifactorial and requires a combination of measures. Our solution is: cohort nursing; non-selective screening of all admissions to the orthopaedic wards; use of a polymerase chain reaction as a diagnostic tool; ring-fencing of beds; and separate wound dressing rooms for each ward. The total cost is projected to be pound301,000.

Meticillin-resistant Staphylococcus aureus carriage among district nurse patients and medical admissions in a UK district

We studied the prevalence of meticillin-resistant Staphylococcus aureus (MRSA) carriage in two defined community populations and assessed risk factors associated with MRSA colonization. The study was designed as a population prevalence survey and was carried out in the medical assessment unit (MAU) of the local hospital and the district nurse patient (DNP) population in Huntingdonshire. In all, 162 participants were recruited, 91 were from MAU and 71 from the DNP population. MRSA was found in 21.1% [confidence interval (CI): 11.6-30.4] of the DNP study population and 6.6% (CI 1.5-11.7) of the MAU study population. Factors found to be significantly associated with MRSA colonization were age (76.6 years, P=0.008), presence of wound/ulcer (P=0.012), hospital admission in the past year (P=0.017), past history of MRSA (P<0.001), and antibiotic use in the preceding six months (P=0.016). The only independent predictor for MRSA colonization was found to be past history of MRSA (adjusted odds ratio: 8.53; CI: 2.11-34.43; P=0.003). The DNP population are a significant reservoir for MRSA in the community and policies on screening high-risk patients need to reflect this.

Managing methicillin-resistant staphylococci: a paradigm for preventing nosocomial transmission of resistant organisms

Multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), are endemic in healthcare settings in the United States and many other countries of the world. Nosocomial transmission of MRSA serves as a source of hospital outbreaks, and recent reports of vancomycin-resistant S aureus strains in the United States emphasize the need for better control of MRSA and other resistant bacteria within healthcare settings. Colonization with S aureus or MRSA is relatively common in both healthy and hospitalized individuals, most often involves the anterior nares, and is frequently asymptomatic. Colonization increases risk of infection. Patient-to-patient transmission of MRSA within healthcare settings primarily occurs via carriage on the hands of healthcare workers. The Society for Healthcare Epidemiology of America (SHEA) has developed guidelines for the prevention of transmission of MRSA and vancomycin-resistant enterococci within healthcare settings, and chief among the recommendations is an emphasis on adherence to hand hygiene guidelines. Other measures that may prevent the nosocomial transmission of MRSA include improved antibiotic stewardship, staff cohorting, maintenance of appropriate staffing ratios, reductions in length of hospital stays, contact isolation, active microbiologic surveillance, and better staff education. Currently, the efficacy of many of these individual infection control interventions remain in doubt. Many studies reporting improvement in infection control outcomes (eg, reduced transmission, decreasing prevalence) involve simultaneous institution of several of these measures, making it impossible to tease out the effects of any of the individual components. Nonetheless, the best approach in the current environment probably involves hand hygiene plus a careful assessment of an institution's particular circumstances, applying more aggressive procedures such as patient isolation, staff cohorting, and active surveillance cultures, as indicated.

Risk factors for hospital-acquired methicillin-resistant Staphylococcus aureus bacteraemia: a case-control study

A case-control study was undertaken in an acute district general hospital to identify risk factors for hospital-acquired bacteraemia caused by methicillin-resistant Staphylococcus aureus (MRSA). Cases of hospital-acquired MRSA bacteraemia were defined as consecutive patients from whom MRSA was isolated from a blood sample taken on the third or subsequent day after admission. Controls were randomly selected from patients admitted to the hospital over the same time period with a length of stay of more than 2 days who did not have bacteraemia. Data on 42 of the 46 cases of hospital-acquired bacteraemia and 90 of the 92 controls were available for analysis. There were no significant differences in the age or sex of cases and controls. After adjusting for confounding factors, insertion of a central line [adjusted odds ratio (aOR) 35.3, 95% confidence interval (CI) 3.8-325.5] or urinary catheter (aOR 37.1, 95% CI 7.1-193.2) during the admission, and surgical site infection (aOR 4.3, 95% CI 1.2-14.6) all remained independent risk factors for MRSA bacteraemia. The adjusted population attributable fraction, showed that 51% of hospital-acquired MRSA bacteraemia cases were attributable to a urinary catheter, 39% to a central line, and 16% to a surgical site infection. In the United Kingdom, measures to reduce the incidence of hospital-acquired MRSA bacteraemia in acute general hospitals should focus on improving infection control procedures for the insertion and, most importantly, care of central lines and urinary catheters.

Frequency and possible infection control implications of gastrointestinal colonization with methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of health care-associated infections. Multiple factors, including transmission from unrecognized reservoirs of MRSA, are responsible for failure to control the spread of MRSA. We conducted prospective surveillance to determine the frequency of gastrointestinal colonization with MRSA among patients and its possible impact on nosocomial transmission of MRSA. Stool specimens submitted for Clostridium difficile toxin A/B assays were routinely inoculated on colistin-naladixic acid agar plates, and S. aureus was identified by using standard methods. Methicillin resistance was confirmed by growth on oxacillin-salt screening agar. For patients whose stool yielded MRSA, information regarding any previous cultures positive for MRSA or other organisms that would require contact precautions was obtained from the laboratory's computer system. During a 1-year period, 151 (9.8%) of 1,543 patients who had one or more stool specimens screened had MRSA in their stool. Ninety-three (62%) of the 151 patients had no previous history of MRSA colonization or infection. Of these 93, 75 were inpatients. Sixty (80%) of the 75 inpatients with no previous history of MRSA were not under "contact precautions." The 60 patients would have spent an estimated total of 267 days without being placed under contact precautions if their positive stool cultures had not resulted in their being isolated. Placing patients under contact precautions based on their positive stool cultures prevented an estimated 35 episodes of MRSA transmission. We conclude that gastrointestinal colonization with MRSA may serve as an unrecognized reservoir from which transmission of MRSA may occur in health care facilities.

Methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci in rural communities, western United States

The impact and prevalence of antimicrobial drug resistance in rural community healthcare settings is uncertain. Prospective surveillance in 51 rural hospitals in Idaho and Utah examined the epidemiologic features of clinical cases of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Thirty-two cases of VRE were reported; for 6, the patient had no prior healthcare exposure or coexisting condition. Among the 724 MRSA cases available for evaluation, 405 (56%) were healthcare-associated (HA-MRSA), and 319 (44%) were community-associated (CA-MRSA). The characteristics of HA-MRSA and CA-MRSA patients with coexisting factors were similar, which suggests community transmission of healthcare strains. CA-MRSA cases without coexisting factors, however, demonstrated features previously reported for community strains. MRSA infections were substantially more frequent than VRE in rural communities in the western United States. Based on epidemiologic criteria, a large proportion of MRSA cases were community-associated. CA-MRSA rates were predictive of institutional MRSA rates.

Prevalence of methicillin-resistant and methicillin-sensitive Staphylococcus aureus nasal colonization among patients at the time of admission to the hospital

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an important agent of hospital-acquired infection. The mode of entry of MRSA in the hospital might be on admission of patients with MRSA infection or nasal colonization. The present study was undertaken to determine the prevalence of MRSA nasal colonization among patients on admission to hospital.

METHODS

Six hundred patients were screened for nasal colonization of MRSA on admission to hospital. Nasal swabs were cultured on salt mannitol agar and blood agar. Age, sex, previous admission to hospital and antibiotic therapy were recorded.

RESULTS

S. aureus was isolated from the nasal swabs of 122 patients (20.2%) on admission to hospital. MRSA was isolated from 7 patients (1.1%) and methicillin-sensitive S. aureus (MSSA) from 115 patients (19.1%). Nasal colonization of S. aureus was higher in younger and elderly patients and significantly higher colonization was observed among females. The MRSA strains isolated from nasal swabs had a different antibiotic susceptibility pattern than those isolated from patients having hospital-acquired MRSA infection. Previous admissions to hospital, underlying disease antibiotic therapy were not risk factors for MRSA nasal colonization.

CONCLUSION

MRSA nasal colonization of patients on admission to hospital is low in this region. The screening of every new admission would not be cost effective, but patients transferred form other institutions should be screened for MRSA. Standard infection control precautions should be strictly implemented to prevent the spread and control of MRSA infections.

Impact of screening for MRSA carriers at hospital admission on risk-adjusted indicators according to the imported MRSA colonization pressure

We evaluated the impact of the different components of a screening programme of methicillin-resistant Staphylococcus aureus (MRSA) carriers at hospital admission on the value of two risk-adjusted rates: the proportion of imported MRSA and an indicator of the MRSA colonization pressure (ICP), and the incidence of MRSA acquired and detected in our hospital. Indicators were calculated: (1) with no screening programme; (2) with a programme limited to the intensive care unit (ICU); (3) with a programme extended to patients with risk factors for MRSA carriage hospitalized in non-ICU wards. The programme included an automatic alert. Systematic sampling of patients with risk factors hospitalized in non-ICU settings detected nearly 50% of carriers at admission. The proportion of MRSA imported into our hospital varied from 35.4% without any screening programme to 71.8% when all components of our screening programme were considered (P<10(-4)). The ICP varied from 3.1% (31/985) with the complete programme to 10.4% (31/297) without any screening programme (P<10(-6)). Screening patients with risk factors for MRSA carriage hospitalized in non-ICU wards resulted in a 51% increase of the calculated proportion of imported strains and a 58% decrease of the ICP. The two studied indicators were strongly dependent on the screening strategy for MRSA carriers implemented at admission. The screening strategy for patients admitted to non-ICU wards who have risk factors for MRSA carriage seems to be the determinant for the interpretation of certain risk-adjusted indicators of MRSA cross-transmission. Comparisons of these indicators must consider the setting in which the screening programmes are implemented.

Choix d’une stratégie de dépistage du Staphylococcus aureus résistant à la méticilline à l’admission en service de soins de suite et de réadaptation

OBJECTIVE

To identify a strategy of MRSA screening (methicillin-resistant Staphylococcus aureus) on admission to geriatric rehabilitation units, which would lead to acceptable efficacy and cost compared with a reference maximaliste strategy combining all six sampling sites. Method MRSA screening was conducted prospectively for 3 months in all the patients admitted to a geriatric follow-up and rehabilitation unit, using samples from the nostrils, armpits, urine scars cutaneous ulcers and sores. Six strategies were defined combing different sampling sites. Their efficacy and cost were compared with those of a maximaliste strategy combining the 6 sampling sites.

RESULTS

Combined screening of all six sites was the most effective but also the most expensive strategy. The least expensive strategy used only samples from ulcers and sores, but its efficacy was of only 45%. The strategy with the lowest loss of efficacy compared to the reference strategy combined the sampling of ulcers and sores and sampling from the nostrils: it was efficient in 91% and its cost was 2.5 fold lower than the cost of the reference strategy.

DISCUSSION

A preliminary, short term study established an MRSA screening strategy adapted to the specificities of a geriatric rehabilitation unit and its recruitment. The ability to define the optimal strategy for MRSA screening in a geriatric rehabilitation and follow-up unit may be an important factor in controlling the diffusion of MRSA.

Prediction rules to identify patients with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci upon hospital admission

BACKGROUND

In 2003, the Society of Healthcare Epidemiology of America (SHEA) recommended surveillance cultures upon hospital admission for patients at high risk for carriage of vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). The aim of this study was to assess the validity of factors from past medical history in defining patients at high risk for subsequent positive cultures with VRE or MRSA upon hospital admission.

METHODS

Subjects were adult inpatients admitted to nonintensive care wards of the index hospital during 2001-2002. Cases had MRSA or VRE positive clinical cultures within 48 hours of hospital admission. Patients with previous history of MRSA or VRE were excluded.

RESULTS

Nineteen thousand three hundred ninety-nine patients were included, with 273 cases of VRE or MRSA. Previous admission within 1 year of current admission had a sensitivity of 56.8% and a specificity of 88.4% for predicting a case of MRSA or VRE. Individually, the sensitivity and specificity for admission within the past year were 50.5% and 88.4%, respectively, for MRSA and 76.9% and 88.4%, respectively, for VRE.

CONCLUSIONS

Patients with a previous hospital admission represent a high-risk population for positive culture for VRE and MRSA and may be a group of which active surveillance is indicated.

Risk factors for postoperative mediastinitis due to methicillin-resistant Staphylococcus aureus

Risk factors for developing postoperative mediastinitis (POM) due to methicillin-resistant Staphylococcus aureus (MRSA) were analyzed in a case-case control study of patients who underwent median sternotomy during the period from 1994 through 2000. Three patient groups were studied. The first consisted of 64 patients with POM due to MRSA; the second consisted of 79 patients with POM due to methicillin-susceptible S. aureus (MSSA); and the third consisted of 80 uninfected control patients. In multivariable analysis, patients who were diabetic (adjusted OR, 2.86; 95% CI, 1.22-6.70), female (OR, 2.70; 95% CI, 1.25-5.88), and >70 years old (OR, 3.43; 95% CI, 1.53-7.71) were more likely to develop POM due to MRSA. In contrast, the only independent risk factor associated with POM due to MSSA was obesity (OR, 2.49; 95% CI, 1.25-4.96). Antimicrobial prophylaxis consisted primarily of cephalosporin antibiotics (administered to 97% of the patients). Changes in perioperative antimicrobial prophylaxis, in addition to other interventions, should be considered for prevention of POM due to MRSA in targeted, high-risk populations.

Comparison of culture screening methods for detection of nasal carriage of methicillin-resistant Staphylococcus aureus: a prospective study comparing 32 methods

Screening for carriage of methicillin-resistant Staphylococcus aureus (MRSA) is fundamental to modern-day nosocomial infection control, both for epidemiologic investigation and day-to-day decisions on barrier isolation. Numerous microbiologic techniques have been advocated for screening for nasal carriage of MRSA, including the use of charcoal rather than rayon swabs, preincubation of swabs in Stuart's medium, preincubation of swabs in salt-containing trypticase soy broth (TSB), use of mannitol-salt agar (MSA), use of MSA containing oxacillin (MSA(Ox)), use of Mueller-Hinton agar containing oxacillin (MHA(Ox)), and the use of MSA containing lipovitellin with an oxacillin disk (MSAL(Ox)). We report a prospective clinical trial undertaken to test all of these methods concurrently. Patients at high risk for MRSA carriage were screened with eight consecutive nasal swabs (four standard rayon, four charcoal-coated rayon), which were processed by primary plating on MSA, MSA(Ox), MHA(Ox), and MSAL(Ox); Stuart's preincubation for 72 h followed by plating on the solid media; overnight enrichment in salt-containing TSB followed by plating; and Stuart's preincubation for 72 h followed by overnight enrichment in TSB and plating. All of the above methods were repeated with charcoal swabs. Each patient was screened by 32 culture methods. Forty-three (42%) of 102 patients studied were positive for MRSA by one or more methods. Among the four media evaluated with direct plating, MSAL(Ox) was 11 to 25% more sensitive for detecting MRSA (MSAL(Ox) versus MSA(Ox) or MHA(Ox) or MSA, each P < 0.01). Preincubation in Stuart's medium for 72 h did not enhance recovery of MRSA. Enrichment in salt-containing TSB further increased yield 9%. MSAL(Ox) also showed the best specificity, 93%. Charcoal swabs showed no advantage over standard rayon swabs. Our results suggest that the highest yield will be achieved by using standard rayon swabs that are enriched overnight in TSB with inoculation onto MSAL(Ox) medium. Direct inoculation of swabs onto MSAL(Ox) allows detection of 90% of MRSA carriers.

Staphylococcal resistance revisited: community-acquired methicillin resistant Staphylococcus aureus--an emerging problem for the management of skin and soft tissue infections

PURPOSE OF REVIEW

In the community non-localized or deep staphylococcal skin and soft tissue infections are typically managed with beta-lactamase stable penicillins. The aims of this review are (1) to evaluate the evidence for the emergence of new strains of community-acquired methicillin resistant Staphylococcus aureus (MRSA), (2) to identify the reasons for their significant association with cutaneous infections, and (3) to consider how they arose and how big a threat they pose to the management of such infections outside hospitals.

RECENT FINDINGS

MRSA are emerging as significant community pathogens, especially in previously healthy children with no recognizable risk factors, and are predominantly associated with skin and soft tissue infections (especially abscesses and cellulitis). When present, risk factors are generally similar to those for infection with methicillin susceptible S. aureus. The MRSA isolates associated with such infections may not be entirely 'new', but could represent the displacement of some hospital clones (e.g. EMRSA-15 or variants thereof) to the community as well as the de-novo generation of novel MRSA clones by multiple horizontal transmissions of the mecA gene into methicillin susceptible S. aureus with different genetic backgrounds, some of which are already circulating globally. Community-acquired MRSA from diverse locations are non multiresistant and almost always contain the novel type IV SCCmec commonly found in coagulase-negative staphylococci, but also in hospital-associated gentamicin susceptible MRSA from France, the paediatric clone and in EMRSA-15.

SUMMARY

More local data on CA-MRSA infections are needed so that dermatologists and community physicians can assess the risk of such infections amongst their patients and avoid the inappropriate administration of beta-lactams. No simple change in prescribing practices will entirely alleviate selective pressure for the spread of community-acquired MRSA and not exacerbate resistance in pyogenic streptococci, commonly found together with S. aureus in skin and soft tissue infections. The importance of hygiene in preventing the spread of community-acquired MRSA in the community must be reemphasized.

Staphylococcus aureus Carriage and Health Care-acquired Infection

Staphylococcus aureus is one of the most common nosocomial pathogens. Its propensity to establish prolonged carriage among hospitalized patients and increasing resistance to antibiotics makes control of this organism within the hospital difficult. High-level vancomycin resistance has now been reported in a single clinical isolate of S. aureus, emphasizing the need to increase efforts to control nosocomial spread. Knowledge of the epidemiology of S. aureus colonization among patients has shed new light on the potential difficulties in interrupting nosocomial transmission. Effective control of S. aureus within the hospital and community will require more aggressive measures that include earlier diagnosis of colonized patients, better handwashing and barrier precaution measures, and renewed efforts to eradicate the carriage state.

[Evaluation of the efficacy of a multiresistant bacteria control programme in a teaching hospital, studying the evolution of methicillin-resistant Staphylococcus aureus incidence]

Methicillin-resistant Staphylococcus aureus (MRSA) constitute the most important multiresistant bacteria (MRB) recovered in French hospitals. Our objective was to measure these MRSA diffusion in our hospital to evaluate the MRB control programme which had been implemented in the beginning of 1999. This study was conducted in a teaching hospital containing 1800 beds, from February 1999 to January 2001. All MRSA isolated in clinical samples were included. Duplicates (same bacteria in the same patient) were excluded. The detection of methicillin-resistance was performed at 30 degrees C, by disk diffusion method. Incidence densities were determined with their 95% confidence interval (CI 95%). Their evolution by four-month period was evaluated with the chi-square test for trend. During the two-year period, 866 MRSA were isolated. The global incidence was 0,88 per 1000 patient-days (PD) (IC 95% = left open bracket 0,83-0,93 right open bracket ). For cases acquired in our hospital the incidence was 0,66 per 1000 PD, whereas it was 0,26 per 1000 PD for imported cases. Concerning the evolution of incidences, no significant trend was observed for global incidence. The incidence of acquired MRSA decreased during the first year, but increased thereafter. The incidence of imported MRSA increased with a significant trend (p < 10(-5)). The number of these imported MRSA isolated in our hospital was twice fold higher in 2000. This study emphasizes an important actual problem : the increase of patient colonization pressure at the time of admission in hospitals. This increase, which can be due in part to a community transmission, is responsible for a reduction of the efficacy of MRSA control programmes.

Population-based community prevalence of methicillin-resistant Staphylococcus aureus in the urban poor of San Francisco

The study objective was to determine the prevalence and risk factors for nasal colonization with Staphylococcus aureus and methicillin resistance among the urban poor and to compare antibiotic resistance and genetic similarity to concurrently collected clinical isolates of methicillin-resistant S. aureus (MRSA). A population-based community sample of 833 homeless and marginally housed adults were cultured and compared with 363 clinical isolates of MRSA; 22.8% of the urban poor were colonized with S. aureus. Of S. aureus isolates, 12.0% were methicillin resistant. Overall prevalence of MRSA was 2.8%. Significant multivariate risk factors for MRSA were injection drug use (odds ratio [OR], 9.7), prior endocarditis (OR, 4.1), and prior hospitalization within 1 year (OR, 2.4). Resistance to antimicrobials other than beta-lactams was uncommon. Only 2 individuals (0.24%) with MRSA had no known risk factors. A total of 22 of 23 community MRSA genotypically matched clinical MRSA isolates, with 15 of 23 isolates identical to MRSA clones endemic among hospitalized patients.

Duration of colonization by methicillin-resistant Staphylococcus aureus after hospital discharge and risk factors for prolonged carriage

To investigate persistent carriage of methicillin-resistant Staphylococcus aureus (MRSA), we conducted a prospective 10-month study of MRSA carriage in previous carriers who were readmitted to our hospital. Four screening specimens, 2 from the skin and 2 from the nares, were obtained within 3 days after admission, in addition to diagnostic specimens requested by physicians. Of the 78 patients included in our study, 31 (40%) were persistent carriers of MRSA, with an estimated median time of 8.5 months to MRSA clearance. In the multivariate analysis, the only factor significantly associated with persistent carriage was the presence of a break in the skin at readmission (odds ratio, 4.34; P=.004); however, a trend was found for admission from a chronic-care institution (odds ratio, 3.65; P=.06). Our data confirm that prolonged carriage of MRSA can occur after hospital discharge, support routine screening for MRSA at readmission of previously MRSA-positive patients, and suggest that a particularly high index of suspicion for MRSA carriage should be maintained if these patients have a break in the skin.

[Changes in epidemiological pattern of methicillin-resistant Staphylococcus aureus infections in a tertiary hospital. Experience of 5 years]

OBJECTIVE

To describe the demographic pattern and tendency of the infections by MRSA between 1992 and 1997.

DESIGN AND METHODS

Descriptive study of the infections by MRSA in a tertiary-care hospital.

RESULTS

267 MRSA infections, 131 infections were included within 58 buds and 136 cases isolated form. The more affected services were Internal Medicine, Urology, Neurology, Vascular surgery and intensive care unit. A tendency was observed to the increase in > 65 years cases and in medical services.

CONCLUSIONS

The increase of elderly cases in medical services and > 65 years carriers in their nose could translate the existent situation in the community.

Methicillin-Resistant Staphylococcus aureus Infections

Methicillin-resistant Staphylococcus aureus (MRSA) has continued to spread and cause serious nosocomial infections. Failure to control MRSA may result in higher rates of use of glycopeptides, which may, in turn, lead to higher rates of glycopeptide resistance. Resistance to glycopeptides has recently begun to appear in S. aureus. Transfer of glycopeptide-resistance genes from enterococci to S. aureus has been documented in laboratory experiments but has not yet been found in clinical isolates. Over time, MRSA is becoming more common in various subsets of the general population. Some studies claim that many MRSA-colonized outpatients and their close contacts have had no health care contacts, but these studies have usually not considered contacts in outpatient clinics. Several other recent studies have found that all or a vast majority of patients with MRSA have had frequent contact with health care providers. Failure to wash hands and disinfect equipment between patients, which has been commonly seen in studies of health care worker compliance with infection control measures, may explain much of the continuing spread. The source of spread of antibiotic-resistant microbes can be likened to an iceberg, with clinically obvious infections representing the tip of the iceberg and most of the spread coming from clinically inapparent colonized patients who represent most of the reservoir for transmission. Surveillance cultures to identify this reservoir are important to the control of spread with effective barrier precautions. Such precautions have been shown to reduce the spread of MRSA 15.6-fold compared with standard precautions.