Control of endemic MRSA-what is the evidence? A personal view

Methicillin-Resistant Staphylococcus Aureus in a General Intensive Care Unit

Methicillin-resistant Staphylococcus aureus (MRSA) has presented special problems in intensive care units (ICUs) because of the difficulties in implementing infection control measures. The prevalence and rate of acquisition of MRSA were studied over thirty months in a nine-bed ICU. Nasal and groin swabs were taken on admission and then weekly, and other cultures as clinically indicated. Of 1361 admissions 119 were MRSA-positive on arrival. 21 cases had been identified before admission and the remainder were detected by screening; in 57 the positive result was known only after discharge. Of the 1242 admissions initially negative 68 acquired MRSA while in the ICU. The ICU had no known MRSA-positive patients on 185 (20.3%) of 914 days, the longest sequence being 17 days. Positive patients occupied 1387 (16.9%) of the 8226 available bed days. Length of stay predicted the risk of acquiring MRSA. Estimated from patients who completed each weekly screening cycle, the risk was 7.5% per week in the first week and 20.3% per week thereafter. The risk was not influenced by initial APACHE II score, the use of haemofiltration, or the number of MRSA-positive patients in the unit. The data suggest that a further 38 of those discharged between weekly screenings acquired MRSA, giving an incidence of 8.5%. MRSA was grown from blood in 17 patients, and from sputum in 53 (ICU-acquired in 18% and 47%). This study suggests that nearly 10% of admissions to a general ICU will be MRSA-positive, of whom only half will be identified before discharge. With standard prevention the risk of previously negative patients acquiring MRSA approximates to 1% per day in the first week and 3% per day thereafter, with nearly one-fifth progressing to bacteraemia; one-half will have MRSA in sputum. Patients with longer stays constitute a high-risk minority for whom additional measures such as decontamination with oropharyngeal and enteral vancomycin should be considered.

Effects of operational decisions on the diffusion of epidemic disease: A system dynamics modeling of the MERS-CoV outbreak in South Korea

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Development of a macro-level health system dynamics model.

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Performance measurements of epidemic disease diffusion and patient-care performance from an operational perspective.

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Comparison of economic and optimal patient room design performance under different infectivity scenarios.

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Comparison of secondary infection outcomes under different ER occupancy circumstances.

We evaluated the nosocomial outbreak of Middle East Respiratory Syndrome (MERS) Coronavirus (CoV) in the Republic of Korea, 2015, from a healthcare operations management perspective. Establishment of healthcare policy in South Korea provides patients’ freedom to select and visit multiple hospitals. Current policy enforces hospitals preference for multi-patient rooms to single-patient rooms, to lower financial burden. Existing healthcare systems tragically contributed to 186 MERS outbreak cases, starting from single “index patient” into three generations of secondary infections. By developing a macro-level health system dynamics model, we provide empirical knowledge to examining the case from both operational and financial perspectives. In our simulation, under base infectivity scenario, high emergency room occupancy circumstance contributed to an estimated average of 101 (917%) more infected patients, compared to when in low occupancy circumstance. Economic patient room design showed an estimated 702% increase in the number of infected patients, despite the overall 98% savings in total expected costs compared to optimal room design. This study provides first time, system dynamics model, performance measurements from an operational perspective. Importantly, the intent of this study was to provide evidence to motivate public, private, and government healthcare administrators’ recognition of current shortcomings, to optimize performance as a whole system, rather than mere individual aspects.

Risk factors for MRSA colonization in dermatologic patients in Germany

BACKGROUND AND OBJECTIVES

Detection of methicillin-resistant Staphylococcus aureus (MRSA) carriage requires well-defined risk factors (RFs). Except for "chronic wounds", RFs are mostly specified in national recommendations. To avoid ineffective and expensive screening, we divided the entity "wounds" into different categories and calculated further RFs in dermatologic patients.

PATIENTS AND METHODS

After a surveillance period with general MRSA screening, we correlated MRSA results with wound categories and dermatologically relevant diagnoses. We analyzed the screening efficacy by adding potential new RFs.

RESULTS

Ulcers (pressure, arterial, combined pressure/arterial ulcers, ulcers otherwise unclassified), type 2 diabetes mellitus (DM), and atopic dermatitis (AD) were significantly associated with MRSA carriage. Tumors (subgroup basal and squamous cell carcinoma) were also significantly associated with MRSA carriage but had a protective odds ratio. Differentiation of wound types did not provide added benefit. In all MRSA-positive patients with chronic wounds, other RKI-listed RFs or type 2 DM were found. Screening sensitivity was increased combining classic RFs (except wounds) with type 2 DM and AD.

CONCLUSIONS

In dermatologic patients, AD and type 2 DM were identified as new RFs. Distinct wound types were also found to be significant RFs, but differentiated screening offers no benefit. When screening patients according to national recommendations, excluding wounds but including type 2 DM and AD, there is no loss of sensitivity.

Isolation and antimicrobial susceptibility pattern of Staphylococcus aureus in patients with surgical site infection at Debre Markos Referral Hospital, Amhara Region, Ethiopia

Background

Staphylococcus aureus, especially Methicillin Resistant Staphylococcus Aureus (MRSA) is a major health problem recognized as the most important nosocomial pathogen, often causing postoperative wound infections. Antibiotic resistance by MRSA has grown to be common, and resistance to almost all antibiotics has been found among these strains. The aim of this study was to determine the prevalence, antimicrobial susceptibility patterns and associated risk factors of S. aureus in patients with surgical site infections in an Ethiopian hospital.

Methods

A cross-sectional study was conducted from December 1, 2011 to March 30, 2012 among patients with surgical site infections at Debre Markos Referral Hospital, Debre Markos, Ethiopia. All wound swabs obtained from patients with surgical site infections during the study period were cultured on mannitol salt agar media which is selective for S. aureus. Isolated strains of S. aureus were tested for antibiotic susceptibility patterns using standard disc diffusion technique, and interpretation of resistance was done based on Clinical and Laboratory Standard Institute criteria. Univariate and multivariable analyses were used to assess the risk factors.

Results

Of the 184 surgical patients who had developed surgical site infection, S. aureus was isolated from 73 (39.7%) cases. Out of the 73 isolates of S. aureus, 36 (49.7%) were MRSA. Among the study participants, prevalence of MRSA was found to be 19.6%. The clinical isolates showed >80% level of resistance to ampicillin, amoxicillin, penicillin G, erythromycin, gentamicin and cotrimoxazole whereas <50% level of resistance was observed against clindamycin, oxacillin, tetracycline and vancomycin. MRSA strains showed resistance ranging from 5.6% (vancomycin) to 100% (cotrimoxazole). Of the following risk factors: sex, age, pus consistency, duration of operation, type of surgery, ward and hospital stay, laparotomy type of surgery was identified as a risk factor for infection by S. aureus.

Conclusion

The prevalence of S. aureus and/or MRSA infection in surgical and gynaecology & obstetrics wards of Debre Markos Referral Hospital was found to be high. The majority of isolates were highly resistant to major antimicrobial agents.

Impact of methicillin resistant Staphylococcus aureus contact isolation units on medical care

BACKGROUND

Patient isolation using contact precautions has gained widespread use to halt MRSA transmission, however supportive data is scarce and concerns regarding patient safety and satisfaction have been raised. At our institution, MRSA patients are isolated on a dedicated ward (cohort isolation), rather than in separate rooms. Our objectives were (1) to determine the proportion of bedside medical visits to patients on an isolation ward, (2) to quantify complications in those patients and (3) to determine if those complications are related to isolation and if they can be prevented.

METHODS

This retrospective case-control study was performed on the two sites of a tertiary teaching hospital in Sherbrooke, QC, Canada. We matched MRSA patients with an admission diagnosis of heart failure or chronic obstructive pulmonary disease to similar non-isolated controls. The proportion of bedside visits was ascertained through the number of progress notes with subjective elements or with a physical examination. Complications were sought through an extensive file review, and events were analysed according to Baker's CAES causality and preventability scales.

RESULTS

Overall, 111 patient pairs were analysed (35 with heart failure and 76 with COPD). Isolated patients received less bedside visits (subjective notes/1,000 patient-days: 849.6 vs. 983.3, p = 0,001). Attending physicians (454.5 vs. 451.4, p = 0,02) and residents (347.0 vs. 416.9, p = 0.01) are responsible for this discrepancy, while medical students appear to visit isolated and non-isolated patients equally (116.5 vs. 114.9, p = 0.90). Isolated patients showed a tendency towards longer stay and more preventable complications, although no difference in the total number of complications was observed.

CONCLUSION

Isolated patients have less documented care that suggests less bedside visits from the medical staff, which could hamper the therapeutical relationship. Further studies are needed to explain this finding.

Long-term risk for readmission, methicillin-resistant Staphylococcus aureus (MRSA) infection, and death among MRSA-colonized veterans

While numerous studies have assessed the outcomes of methicillin-resistant S. aureus (MRSA) colonization over the short term, little is known about longer-term outcomes after discharge. An assessment of long-term outcomes could provide information about the utility of various MRSA prevention approaches. A matched-cohort study was performed among Veterans Affairs (VA) patients screened for MRSA colonization between the years 2007 and 2009 and followed to evaluate outcomes until 2010. Cox proportional-hazard models were used to evaluate the association between MRSA colonization and long-term outcomes, such as infection-related readmission and crude mortality. A total of 404 veterans were included, 206 of whom were MRSA carriers and 198 of whom were noncarriers. There were no culture-proven MRSA infections on readmission among the noncarriers, but 13% of MRSA carriers were readmitted with culture-proven MRSA infections on readmission (P < 0.01). MRSA carriers were significantly more likely to be readmitted, to be readmitted more than once due to proven or probable MRSA infections, and to be readmitted within 90 days of discharge than noncarriers (P < 0.05). Infection-related readmission (adjusted hazard ratio [HR] = 4.07; 95% confidence interval [CI], 2.16 to 7.67) and mortality (adjusted HR = 2.71; 95% CI, 1.87 to 3.91) were significantly higher among MRSA carriers than among noncarriers after statistically adjusting for potential confounders. Among a cohort of VA patients, MRSA carriers are at high risk of infection-related readmission, MRSA infection, and mortality compared to noncarriers. Noncarriers are at very low risk of subsequent MRSA infection. Future studies should address whether interventions such as nasal or skin decolonization could result in improved outcomes for MRSA carriers.

Triple swabbing allows sensitive MRSA detection in dermatologic patients of a university tertiary care hospital

BACKGROUND

To optimize preventive measures to control MRSA, we investigated retrospectively the suitability of a multiple site screening model and the optimal sampling technique to detect MRSA in a university-based phlebology and skin cancer center in Germany.

PATIENTS AND METHODS

During 4.5 years samples of 3 712 inpatients in a dermatologic department were analyzed for MRSA by conventional microbiologic cultures and in parallel by PCR. Samples were taken from nares, wounds and skin lesions.

RESULTS

MRSA was detected in 60 inpatients (1.6%). 268 of 7 269 (3.7%) samples at admission and during hospital stay were found positive ñ 96 (35.8%) of these were swabs of nares, 59 (22.0%) surveillance swabs, 53 (19.8%) wound swabs and 42 (15.7%) from other dermatologic lesions. Twenty-five of 60 patients (41.7%) were found positive only in the nares, 10 (16.7%) patients only in wounds and 4 (6.7%) patients only in lesions. 166 (61.9%) of all positive culture samples became positive 24 hours after cultivation, 86 (32.1%) after 48 hours, and 16 (6.0%) after 72 hours.

CONCLUSIONS

Highest sensitivity to detect MRSA can be reached by combining three swabs: nares, wounds and skin lesions (ìtriple-testî). Culture of screening specimens for 72 hours is recommended.

A multilevel model of methicillin-resistant Staphylococcus aureus acquisition within the hierarchy of an Australian tertiary hospital

Hospitals without universal single room accommodations typically contain multibed cubicles within wards. In this study, we examined whether the variation in a patient's risk for acquiring methicillin-resistant Staphylococcus aureus (MRSA) in a major tertiary hospital was greatest at the bed, cubicle, or ward level, and quantified the risk of MRSA acquisition associated with exposure to MRSA-colonized/infected patients within the same bed, cubicle, and ward at differently distributed lag times. Nested tri-level hierarchical logistic regression models with random effects were used for non-multiresistant MRSA (nmMRSA) and multiresistant MRSA (mMRSA). The models were internally validated. Receiver operating characteristic curves were used to compare the models' predictive capability The odds of new nmMRSA acquisition were 6.06-fold (95% credible intervals [CrI], 3.93- to 9.34-fold) greater in bed-weeks when a nmMRSA-colonized/infected patient was in the same cubicle 2 weeks earlier. The odds of mMRSA acquisition were 5.12-fold (95% CrI, 4.02- to 6.51-fold) greater in bed-weeks when a colonized/infected patient was in the same ward 2 weeks earlier. The between-cluster variance was highest at the ward level. Patients were at greater risk if there was a colonized/infected patient in the same cubicle or ward 2 weeks earlier. Our findings indicate that focusing on the relevant cubicles and wards during this high-risk period can help target infection control resources more efficiently.

Isolation of Staphylococcus Aureus and Progression of Periodontal Lesions in Aggressive Periodontitis

This work evaluates whether isolation and toxicity of subgingival Staphylococcus aureus strains correlate with progression of periodontal lesions and whether isolates are characterized by a specific genomic background. The study involved 165 subjects affected by generalized aggressive periodontitis. Three sets of samples of supragingival and subgingival plaque were obtained at 45-day intervals from active and non-active sites, to detect S. aureus. Susceptibility to antibiotics, the presence of 17 genes, genomic restriction profiles and multilocus sequence typing (MLST) were performed to characterize all isolates. S. aureus was detected in 37.6% of the subjects. Subgingival colonization rates were 66.1% and 12.9% for active and non-active sites, respectively ( P<0.01). Supragingival and subgingival isolates were shown to be distinct by molecular genotyping and DNA fingerprint analysis. MLST showed that isolates were not genetically related and no sequence type was predominant in any of the two locations. These data demonstrate that S. aureus is associated with the progression of aggressive periodontitis and that a specific set of characters is necessary for the bacterium to colonize subgingival sites. Comparative analysis of genomic structure and genetic-related data suggest that the periodontal environment could promote genetic evolution of strains.

Infection prevention practice: how does experience affect knowledge and application?

The purpose of this study was to evaluate nurses’ knowledge of infection prevention procedures, the degree to which they were applied correctly, and whether length of service affected either knowledge or application. Nurses with over five years of experience had significantly increased understanding of infection prevention ( p=0.009) and significantly increased application of knowledge to practice ( p=0.001), compared to nurses with five years or less experience. In particular, understanding of hand hygiene and use of personal protective equipment (PPE) was poor although application was compliant, while knowledge of care of patients with meticillin resistant Staphylococcus aureus (MRSA) and Clostridium difficile was poor, which was reflected by substandard application of knowledge to practice. The results of this study suggest that focusing infection prevention education around patients with specific infections, such as MRSA and C. difficile, rather than on individual standard precautions may more effectively increase knowledge and therefore application of infection prevention practices.

Single-nucleotide polymorphism genotyping identifies a locally endemic clone of methicillin-resistant Staphylococcus aureus

We developed, tested, and applied a TaqMan real-time PCR assay for interrogation of three single-nucleotide polymorphisms that differentiate a clade (termed 't003-X') within the radiation of methicillin-resistant Staphylococcus aureus (MRSA) ST225. The TaqMan assay achieved 98% typeability and results were fully concordant with DNA sequencing. By applying this assay to 305 ST225 isolates from an international collection, we demonstrate that clade t003-X is endemic in a single acute-care hospital in Germany at least since 2006, where it has caused a substantial proportion of infections. The strain was also detected in another hospital located 16 kilometers away. Strikingly, however, clade t003-X was not found in 62 other hospitals throughout Germany nor among isolates from other countries, and, hence, displayed a very restricted geographical distribution. Consequently, our results show that SNP-typing may be useful to identify and track MRSA clones that are specific to individual healthcare institutions. In contrast, the spatial dissemination pattern observed here had not been resolved by other typing procedures, including multilocus sequence typing (MLST), spa typing, DNA macrorestriction, and multilocus variable-number tandem repeat analysis (MLVA).

Screening and control of methicillin-resistant Staphylococcus aureus in 186 intensive care units: different situations and individual solutions

Introduction

Controversy exists about the benefit of screening for prevention of methicillin-resistant Staphylococcus aureus (MRSA) in intensive care units (ICUs) and recent studies have shown conflicting results. The aim of this observational study was to describe and evaluate the association between MRSA incidence densities (IDs) and screening and control measures in ICUs participating in the German Nosocomial Infection Surveillance System.

Methods

The surveillance module for multidrug-resistant bacteria collects data on MRSA cases in ICUs with the aim to provide a national reference and a tool for evaluation of infection control management. The median IDs of MRSA cases per 1000 patient-days (pd) with the interquartile range (IQR) were calculated from the pooled data of 186 ICUs and correlated with parameters derived from a detailed questionnaire regarding ICU structure, microbiological diagnostics and MRSA screening and control measures. The association between questionnaire results and MRSA cases was evaluated by generalized linear regression models.

Results

One hundred eighty-six ICUs submitted data on MRSA cases for 2007 and 2008 and completed the questionnaire. During the period of analysis, 4935 MRSA cases occurred in these ICUs; of these, 3928 (79.6%) were imported and 1007 MRSA cases (20.4%) were ICU-acquired. Median MRSA IDs were 3.23 (IQR 1.24-5.73), 2.24 (IQR 0.63-4.30) and 0.64 (IQR 0.17-1.39) per 1000 pd for all cases, imported and ICU-acquired MRSA cases, respectively. MRSA IDs as well as implemented MRSA screening and control measures varied widely between ICUs. ICUs performing universal admission screening had significantly higher MRSA IDs than ICUs performing targeted or no screening. Separate regression models for ICUs with different screening strategies included the incidence of imported MRSA cases, the type of ICU, and the length of stay in independent association with the number of ICU-acquired MRSA cases.

Conclusions

The analysis shows that MRSA IDs and structural parameters differ considerably between ICUs. In response, ICUs have combined screening and control measures in many ways to achieve various individual solutions. The incidence of imported MRSA cases might be helpful for consideration in the planning of MRSA control programmes.

MRSA prevalence in European healthcare settings: a review

BACKGROUND

During the past two decades, methicillin-resistant Staphylococcus aureus (MRSA) has become increasingly common as a source of nosocomial infections. Most studies of MRSA surveillance were performed during outbreaks, so that results are not applicable to settings in which MRSA is endemic. This paper gives an overview of MRSA prevalence in hospitals and other healthcare institutions in non-outbreak situations in Western Europe.

METHODS

A keyword search was conducted in the Medline database (2000 through June 2010). Titles and abstracts were screened to identify studies on MRSA prevalence in patients in non-outbreak situations in European healthcare facilities. Each study was assessed using seven quality criteria (outcome definition, time unit, target population, participants, observer bias, screening procedure, swabbing sites) and categorized as 'good', 'fair', or 'poor'.

RESULTS

31 observational studies were included in the review. Four of the studies were of good quality. Surveillance screening of MRSA was performed in long-term care (11 studies) and acute care (20 studies). Prevalence rates varied over a wide range, from less than 1% to greater than 20%. Prevalence in the acute care and long-term care settings was comparable. The prevalence of MRSA was expressed in various ways - the percentage of MRSA among patients (range between 1% and 24%), the percentage of MRSA among S. aureus isolates (range between 5% and 54%), and as the prevalence density (range between 0.4 and 4 MRSA cases per 1,000 patient days). The screening policy differed with respect to time points (on admission or during hospital stay), selection criteria (all admissions or patients at high risk for MRSA) and anatomical sampling sites.

CONCLUSIONS

This review underlines the methodological differences between studies of MRSA surveillance. For comparisons between different healthcare settings, surveillance methods and outcome calculations should be standardized.

Infection in the critically ill--questions we should be asking

Best practice in infection control and management in the critically ill continues to generate considerable debate. The wide variation in current practice is witness to this continuing uncertainty. In large part this is due to the lack of a decent evidence base and to an over-reliance on deep-set dogma. Data that go against the grain are often conveniently overlooked and political imperatives frequently supervene. This article highlights some of these discrepancies and argues for a more balanced, scientific approach. In this time of financial restraint, we need to identify true priorities from both health and economic perspectives, and to see what practices can safely and effectively be modified or abandoned.

Community-associated methicillin-resistant Staphylococcus aureus, Iowa, USA

We performed antimicrobial drug susceptibility testing and molecular typing on invasive methicillin-resistant Staphylococcus aureus (MRSA) isolates (n = 1,666) submitted to the University of Iowa Hygienic Laboratory during 1999-2006 as part of a statewide surveillance system. All USA300 and USA400 isolates were resistant to <or=3 non-beta-lactam antimicrobial drug classes. The proportion of MRSA isolates from invasive infections that were either USA300 or USA400 increased significantly from 1999-2005 through 2006 (p<0.0001). During 2006, the incidence of invasive community-associated (CA)-MRSA infections was highest in the summer (p = 0.0004). Age <69 years was associated with an increased risk for invasive CA-MRSA infection (odds ratio [OR] 5.1, 95% confidence interval [CI] 2.06-12.64), and hospital exposure was associated with decreased risk (OR 0.07, 95% CI 0.01-0.51).

[Prevention of transmission of methicillin-resistant Staphylococcus aureus (MRSA) infection: standard precautions instead of isolation: a 6-year surveillance in a university hospital]

BACKGROUND

This study was carried out to evaluate whether the risk of acquiring methicillin-resistant Staphylococcus aureus (MRSA) is increased compared to reference data when standard precautions are practiced instead of strict or contact isolation.

METHODS

From 2000 through 2005, all patients with MRSA at a university hospital were prospectively surveyed. The isolates were investigated using molecular microbiology methods (PFGE, PCR) and compliance with hand hygiene was indirectly monitored using the consumption of disinfection solutions and glove use as surrogate markers.

RESULTS

The MRSA rates of the 797 patients were lower than for the reference data (PEG, KISS), the incidence of MRSA infections was reduced continuously, MRSA transmissions to contact patients could be demonstrated in about 30%, and the consumption of hand disinfection solutions as well as gloves was significantly higher in 2005 compared to 2000.

CONCLUSIONS

There is no evidence from our results that practicing standard precautions would increase the risk for the acquisition of MRSA compared to strict or contact isolation.

Screening and isolation for infection control

Control measures aimed to reduce the prevalence of healthcare-associated infections include active surveillance cultures (ASCs), contact isolation of patients colonised with epidemiologically significant pathogens, and pre-emptive isolation of high risk patients. However, the benefits of these measures are questionable. A systematic review of isolation policies demonstrated that intensive concerted interventions including isolation can substantially reduce nosocomial meticillin-resistant Staphylococcus aureus (MRSA) infection. Monitoring of interventions is fundamental. Surveillance data should be presented and fed back appropriately. International guidelines suggest that only intensive care units should apply extensive ASCs. However, legislation for mandatory screening at hospital admission has been advocated in many countries. Targeted screening could be used to limit the potential for dissemination of antibiotic-resistant pathogens from otherwise unsuspected carriers from the start of patients' hospitalisation, as opposed to other strategies, in which screening programmes target patients already hospitalised. Although the influx of antibiotic-resistant pathogens into the hospital would not change, early detection would reduce the time colonised patients might have to disseminate pathogens. Recently, rapid methods for molecular detection of MRSA have been developed. Data on the impact of these tests on the MRSA acquisition rate are extremely heterogeneous. Published studies differ according to the settings in which they have been evaluated, the choice of patient population to be screened, other infection control measures employed and, most importantly, study design and baseline prevalence of MRSA. Based on these studies, definitive recommendations cannot be made.

[Methicillin-resistant Staphylococcus aureus (MRSA) infections. Epidemiology, diagnostics, therapy, and prevention]

The increasing number of complicated soft-tissue or invasive infections caused by methicillin-resistant Staphylococcus aureus (MRSA) is a frequent reason for elaborate treatment regimens. Unidentified MRSA carriers may be the origin of endemic spread to other patients and medical staff. Recently, community-associated cMRSA with particular virulence factors were isolated from persons without the typical history of hospital contacts. Molecular tools for the timely detection of the mecA resistance gene for the identification of MRSA in medical test specimens have become a standard approach in MRSA-related diagnostic procedures. The actual therapy of MRSA infections requires consideration of both the appropriate spectrum of activity and the adequate pharmacological properties of a chosen antimicrobial. Preventive strategies rely on the consistent application of standard hygiene precautions, which have to be supplemented with increased barriers for the isolation of identified MRSA patients.

Infection control and prevention in perioperative practice

The personal and financial consequences of avoidable infection are enormous in personal and global terms (DH 2003, Stone, Larson & Kawar 2002). Patients expect to be treated and cared for in clean conditions, and not be exposed to the risks of acquiring an infection by poor practice on the part of healthcare workers (DH 2005, Health Care Commission 2005). Infection control and prevention in perioperative settings assumes an even greater significance because of the vulnerability of patients who are already ill or injured, and because surgery, anaesthesia and immediate postoperative recovery may expose them to invasive procedures, allowing more portals of entry for infection. There is ample evidence, widely available, to support best practice in all healthcare settings. The methods are cheap, easy to apply and very effective (Wright 2004, Pratt et al 2007). This article will examine a range of evidence applicable to perioperative infection control and prevention, including an assessment of current practice and how it may be improved, with a particular emphasis on surgical site infection associated with Meticillin Resistant Staphylococcus Aureus (MRSA) and Clostridium Difficile (C.diff).

Sustainability of land application of class B biosolids

Land application of Class B biosolids is routinely undertaken in the United States. However, due to public concern over potential hazards, the long-term sustainability of land application has been questioned. Thus, the objective of this review article was to evaluate the sustainability of land application of Class B biosolids. To do this we evaluated (i) the fate and transport of potential biological and chemical hazards within biosolids, and (ii) the influence of long-term land application on the microbial and chemical properties of the soil. Direct risks to human health posed by pathogens in biosolids have been shown to be low. Risks from indirect exposure such as aerosolized pathogens or microbially contaminated ground water are also low. A long-term land application study showed enhanced microbial activity and no adverse toxicity effects on the soil microbial community. Long-term land application also increased soil macronutrients including C, N, and, in particular, P. In fact, care should be taken to avoid contamination of surface waters with high phosphate soils. Available soil metal concentrations remained low over the 20-yr land application period due to the low metal content of the biosolids and a high soil pH. Soil salinity increases were not detected due to the low salt content of biosolids and irrigation rates in excess of consumptive use rates for cotton. Our conclusion, based on these studies, is that long-term land application of Class B biosolids is sustainable.

Control of endemic methicillin-resistant Staphylococcus aureus--recent advances and future challenges

Although the exact burden of disease caused by methicillin-resistant Staphylococcus aureus (MRSA) remains largely unknown, most experts agree that MRSA infections are an important clinical and public health problem. Thousands of reports have been published during the last four decades concerning epidemiological and microbiological aspects of MRSA, but uncertainty remains about the best approach to prevent and control this worldwide plague, especially endemic MRSA. Epidemiological methods, e.g., risk scores for targeted screening upon admission, rapid molecular tests and pre-emptive isolation of high-risk patients, new decontamination regimens and restriction of certain antibiotic classes, are all promising approaches that may decrease MRSA cross-transmission; however, further evidence is needed before these strategies can be implemented on a wide scale. Control of community MRSA is an additional challenge for the future, requiring improved surveillance and contact tracing, as well as education and treatment of both infected cases and colonised contacts. This review summarises recent advances and studies that address these issues. Overall, it seems that there is no level of MRSA prevalence for which active control measures are no longer warranted.

Throat and rectal swabs may have an important role in MRSA screening of critically ill patients

OBJECTIVE

Methicillin-resistant Staphylococcus aureus (MRSA) is a major problem in intensive care units (ICU). International guidelines recommend screening patients for MRSA on admission, although consensus on sites required for optimum detection has not been reached. Our aim was to determine whether throat and rectal swabs identified a significant number of additional MRSA-colonised patients not captured by swabbing at keratinized skin carriage sites (anterior nares, perineum and axillae).

DESIGN

Prospective cohort study.

SETTING

30-Bed medical and surgical ICU in a tertiary teaching hospital.

PATIENTS

One thousand four hundred and eighty adult patients consecutively admitted over 15 months.

MEASUREMENTS AND RESULTS

Swabs from carriage sites (anterior nares, perineum, axillae, throat and rectum), wounds and clinical samples taken within 48 h of ICU admission were analysed to identify patients admitted with MRSA. A complete set of carriage swabs were received from 1,470 patients. 105 (7%) patients were admitted with MRSA of which 63 (60%) were detected by a pooled keratinized skin swab (anterior nares, perineum, axillae). A further 36 (34%) patients were detected only by throat or rectal swabs. Indeed, throat and rectal swabs combined had a higher sensitivity than pooled keratinised skin swabs (76 vs. 60% P = 0.0247). Swabs from all carriage sites together detected 95% (100) of MRSA positive patients, with five patients being positive at wound sites only.

CONCLUSIONS

The throat and rectum are important and potentially hidden sites of MRSA carriage in critically ill patients. These findings prompt the need for larger studies to determine the most cost-effective screening strategy for MRSA detection.

DESCRIPTOR

Non-pulmonary nosocomial infections.

Antioxidant and antimicrobial activities of native Rosa sp. from British Columbia, Canada

Indigenous traditional knowledge and western science have revealed the potential for significant nutritional and therapeutic benefits among natural antioxidants. We investigated antioxidant and antimicrobial activity of rose hip extracts (Rosa nutkana, Rosa pisocarpa and Rosa woodsii) from wild British Columbia populations using liposome oxidation and disc diffusion assays. All extracts exhibited strong antioxidant activity. R. nutkana pericarp extracts contained high phenolic concentrations and showed greater antioxidant and antimicrobial activity than seed extracts. R. woodsii seed extracts had a higher phenolic concentration and greater antioxidant activity than pericarp extracts. Antioxidant activity was correlated with antimicrobial activity, and both extracts showed antimicrobial activity against yeast and Gram-positive bacteria. Our study is the first to demonstrate the antioxidant and antimicrobial properties of wild British Columbia roses. The effectiveness of selected species compared with standards demonstrates the significance of this natural resource to the continued health of human populations, and the need for conservation practices.

Occurrence of antibiotic-resistant bacteria and endotoxin associated with the land application of biosolids

The purpose of this study was to determine the prevalence of antibiotic-resistant bacteria and endotoxin in soil after land application of biosolids. Soil was collected over a 15 month period following land application of biosolids, and antibiotic resistance was ascertained using clinically relevant antibiotic concentrations. Ampicillin, cephalothin, ciprofloxacin, and tetracycline resistance were all monitored separately for any changes throughout the 15 month period. Endotoxin soil concentrations were monitored using commercially available endotoxin analysis reagents. Overall, land application of biosolids did not increase the percentage of antibiotic-resistant culturable bacteria above background soil levels. Likewise, land application of biosolids did not significantly increase the concentration of endotoxin in soil. This study determined and established a baseline understanding of the overall effect that land application of biosolids had on the land-applied field with respect to antibiotic-resistant bacterial and endotoxin soil densities.

Impact of infection control interventions and antibiotic use on hospital MRSA: a multivariate interrupted time-series analysis

Hospitals in the northeast of Scotland have experienced methicillin-resistant Staphylococcus aureus (MRSA) outbreaks since 1997. Several infection control measures were introduced sequentially to control MRSA, and antibiotic use has been monitored. From January 1997 to December 2004, data on the monthly percentage of non-duplicate MRSA infections (%MRSA) were collated from an intervention hospital (IH) and a control hospital (CH). Both hospitals introduced the use of alcohol hand gel in November 2002. Furthermore, the IH introduced an environmental MRSA swabbing programme in March 2001, chlorine disinfection of the environment in September 2001, discharge screening in December 2001, admission screening in November 2003 and environmental audits in March 2004. Multivariate dynamic regression analysis was used to evaluate the longitudinal effects of these interventions as measured by new clinical cases of MRSA. At the IH, the %MRSA increased between January 1998 and January 2001 and then decreased. At the CH, the %MRSA increased from January 1997 to December 2004. Introduction of alcohol hand gel was associated with an absolute decrease in %MRSA of 21% and 30%, respectively, for the IH and CH. At the IH, introduction of chlorine disinfection and environmental swabbing were, respectively, associated with a decrease in %MRSA of 27% immediately and 32% 3 months later. Discharge screening and environmental audit did not significantly affect %MRSA, whereas admission screening was associated with a 22% decrease in %MRSA 4 months later. Increasing macrolide use was associated with increasing %MRSA in both hospitals, and increasing quinolone use was associated with increasing %MRSA in the CH. Implementation of stepwise infection control measures was associated with a decrease in %MRSA in the IH. Introduction of an alcohol gel for hand hygiene was associated with a decrease in %MRSA in both hospitals. Antibiotic use also affects %MRSA, in particular that of macrolides and quinolones.

Patients’ feelings about hand washing, MRSA status and patient information

The purpose of this study was to explore patient opinion about asking healthcare professionals to wash their hands before a clinical procedure and to explore if methicillin-resistant Staphylococcus aureus (MRSA) status and access to patient information about infection control would influence the patients' anxiety about asking. A descriptive survey was undertaken using a semi-structured questionnaire. The questionnaire was distributed to a randomized convenience sample of 185 inpatients across all departments of an acute NHS Trust hospital (response rate 58.9%). Spearman's rank order and Kendall Tau-b tests were used to analyse specific correlations. Respondents were more confident than anxious about being involved in a campaign that empowered patients to ask staff to wash their hands. Patients were more anxious to ask if their previous admission episodes were fewer, if their knowledge of MRSA was high and if there was less information about infection control available. Patients who had contracted MRSA in the past were less anxious, as they had a better understanding of the disease. In addition, more patients felt less anxious about asking staff to wash their hands if staff wore a badge saying 'It's OK to ask'.

Control and prevention of MRSA infections

Methicillin-resistant Staphylococcus aureus (MRSA) has posed an immense problem for clinicians in the hospital setting for years, emerging as the most frequent nosocomial infection. To deal with this problem pathogen and others, infectious disease specialists have developed a variety of procedures for their control and prevention, involving options from preventative measures such as decolonization and isolation of MRSA-confirmed patients, to the more simple procedures of hand washing, expanding glove use, and reducing time in the hospital. With the realization that MRSA is now a community problem, there are expanded efforts toward more direct intervention, such as the use of anti-MRSA antibacterials and vaccines, in an attempt to reduce the overall burden of MRSA.

Methicillin-resistant Staphylococcus aureus colonization in veterinary personnel

Methicillin-resistant Staphylococcus aureus (MRSA) was isolated from nares of 27/417 (6.5%) attendees at an international veterinary conference: 23/345 (7.0%) veterinarians, 4/34 (12.0%) technicians, and 0/38 others. Colonization was more common for large-animal (15/96, 15.6%) than small-animal personnel (12/271, 4.4%) or those with no animal patient contact (0/50) (p<0.001). Large-animal practice was the only variable significantly associated with colonization (odds ratio 2.9; 95% confidence interval 1.2-6.6). Pulsed-field gel electrophoresis identified 2 predominant clones with similar distribution among veterinarians as previously reported for horses and companion animals. Canadian epidemic MRSA-2 (CMRSA) was isolated from 11 small-animal and 2 large-animal personnel from the United States (n = 12) and Germany (n = 1). In contrast, CMRSA-5 was isolated exclusively from large-animal personnel (p<0.001) in the United States (n = 10), United Kingdom (n = 2), and Denmark (n = 1). MRSA colonization may be an occupational risk for veterinary professionals.

[Positive screening for MRSA--clinical consequences?]

BACKGROUND

The worldwide rise of MRSA is equivalent to an increase of nasal colonization with MRSA. The objectives of this study were to investigate the rate of occult nasal MRSA colonization in trauma patients, to elucidate the role of MRSA carriers for endogenous infection (nose --> wound) and to check the efficiency of mupirocin therapy.

PATIENTS AND METHODS

A total of 643 consecutive trauma patients underwent MRSA screening (nasal swabs) on admission. At the same time all MRSA wound infections were registered and all isolates were analysed with PFGE (pulsed-field gel electrophoresis) to detect cross-infection between individuals.

RESULTS

In 13 patients (2.0%) we found MRSA in the nose and limited isolation as well as therapy with mupirocin were performed. No endogenous transmission of MRSA from the nose to the wound could be seen, and no cross-infection to other patients could be detected.

CONCLUSION

Our findings suggest that in our patients with nasal colonization the risk of intra- and interindividual transmission of MRSA is very small. Therefore, in trauma patients screening on admission does not seem to be absolutely necessary either for clinical or for epidemiological reasons.

Evaluation of rapid screening and pre-emptive contact isolation for detecting and controlling methicillin-resistant Staphylococcus aureus in critical care: an interventional cohort study

INTRODUCTION

Rapid diagnostic tests may allow early identification of previously unknown methicillin-resistant Staphylococcus aureus (MRSA) carriers at intensive care unit (ICU) admission. The aim of this study was twofold: first, to assess whether a new molecular MRSA screening test can substantially decrease the time between ICU admission and identification of MRSA carriers; and, second, to examine the combined effect of rapid testing and pre-emptive contact isolation on MRSA infections.

METHOD

Since November 2003, patients admitted for longer than 24 hours to two adult ICUs were screened systematically on admission using quick, multiplex immunocapture-coupled PCR (qMRSA). Median time intervals from admission to notification of test results were calculated for a five-month intervention phase (November 2003-March 2004) and compared with a historical control period (April 2003-October 2003) by nonparametric tests. ICU-acquired MRSA infection rates were determined for an extended surveillance period (January 2003 through August 2005) and analyzed by Poisson regression methods.

RESULTS

During the intervention phase, 97% (450/462) of patients admitted to the surgical ICU and 80% (470/591) of patients admitted to the medical ICU were screened. On-admission screening identified the prevalence of MRSA to be 6.7% (71/1053). Without admission screening, 55 previously unknown MRSA carriers would have been missed in both ICUs. Median time from ICU admission to notification of test results decreased from 87 to 21 hours in the surgical ICU (P < 0.001) and from 106 to 23 hours in the medical ICU (P < 0.001). In the surgical ICU, 1,227 pre-emptive isolation days for 245 MRSA-negative patients were saved by using the qMRSA test. After adjusting for colonization pressure, the systematic on-admission screening and pre-emptive isolation policy was associated with a reduction in medical ICU acquired MRSA infections (relative risk 0.3, 95% confidence interval 0.1-0.7) but had no effect in the surgical ICU (relative risk 1.0, 95% confidence interval 0.6-1.7).

CONCLUSION

The qMRSA test decreased median time to notification from four days to one day and helped to identify previously unknown MRSA carriers rapidly. A strategy linking the rapid screening test to pre-emptive isolation and cohorting of MRSA patients substantially reduced MRSA cross-infections in the medical but not in the surgical ICU.

Active surveillance for methicillin-resistant Staphylococcus aureus (MRSA) decreases the incidence of MRSA bacteremia

OBJECTIVES

To evaluate the influence of performance of active surveillance cultures for methicillin-resistant Staphylococcus aureus (MRSA) on the incidence of nosocomial MRSA bacteremia in an endemic hospital.

DESIGN

Before-after trial.

SETTING

A 700-bed hospital.

PATIENTS

All patients admitted to the hospital who were at high risk for MRSA bacteremia.

INTERVENTION

Performance of surveillance cultures for detection of MRSA were recommended for all patients at high risk, and contact isolation was implemented for patients with positive results of culture. Each MRSA-positive patient received one course of eradication treatment. We compared the total number of surveillance cultures, the percentage of surveillance cultures with positive results, and the number of MRSA bacteremia cases before the intervention (from January 2002 through February 2003) after the start of the intervention (from July 2003 through October 2004).

RESULTS

The number of surveillance cultures performed increased from a mean of 272.57 cultures/month before the intervention to 865.83 cultures/month after the intervention. The percentage of surveillance cultures with positive results increased from 3.13% before to 5.22% after the intervention (P < .001). The mean number of MRSA bacteremia cases per month decreased from 3.6 cases before the intervention to 1.8 cases after the intervention (P < 0.001).

CONCLUSIONS

Active surveillance culture is important for identifying hidden reservoirs of MRSA. Contact isolation can prevent new colonization and infection and lead to a significant reduction of morbidity and healthcare costs.

Emergence and resurgence of meticillin-resistant Staphylococcus aureus as a public-health threat

Staphylococcus aureus is a gram-positive bacterium that colonises the skin and is present in the anterior nares in about 25-30% of healthy people. Dependent on its intrinsic virulence or the ability of the host to contain its opportunistic behaviour, S aureus can cause a range of diseases in man. The bacterium readily acquires resistance against all classes of antibiotics by one of two distinct mechanisms: mutation of an existing bacterial gene or horizontal transfer of a resistance gene from another bacterium. Several mobile genetic elements carrying exogenous antibiotic resistance genes might mediate resistance acquisition. Of all the resistance traits S aureus has acquired since the introduction of antimicrobial chemotherapy in the 1930s, meticillin resistance is clinically the most important, since a single genetic element confers resistance to the most commonly prescribed class of antimicrobials--the beta-lactam antibiotics, which include penicillins, cephalosporins, and carbapenems.

Impact of the reinforcement of a Methicillin-Resistant Staphylococcus aureus Control Programme: A 3-year evaluation by several indicators in a French University Hospital

Our objective was to evaluate the impact of the reinforcement of a methicillin-resistant Staphylococcus aureus (MRSA) control programme and to assess the impact of risk adjustment on the interpretation of data. A stepwise, retrospective analysis of 3-year prospectively collected data was performed in a 600-bed French teaching hospital in the Parisian area. A reinforcement of a pre-existing programme for limiting the spread of MRSA was implemented in 2002 and 2003 by increasing the frequency of the feedback of surveillance data, by using alcohol-based disinfectants, and by increasing patient screening. Different indicators were used to follow the change over time of MRSA transmission: the proportion of MRSA acquired in our hospital, the incidence of newly acquired MRSA/1,000 patient-days (PD) (incidence of newly acquired MRSA), the incidence of newly acquired MRSA isolated in at least one clinical specimen/1,000 PD (incidence of newly acquired clinical MRSA), and a risk-adjusted indicator, the incidence of newly acquired-MRSA isolated in at least one clinical specimen/1,000 PD of carriers identified at admission (incidence related to the risk of acquisition). The change over time of these indicators was studied with the chi-square test for trend. During the study, all indicators decreased significantly, with a mean drop of 0.07/1,000 PD for the incidence of newly acquired clinical MRSA, and a mean drop of 3.0/1,000 PD for the incidence related to the risk of acquisition. The proportion of MRSA acquired in our hospital decreased from 49.3% in 2002 to 24.1% in 2004. Concurrently, between 2002 and 2004, the number of patients screened on admission to hospital or at the time of intra-hospital transfer increased by 31% and the consumption of waterless alcohol-based hand disinfectants increased by 244%. The decreasing trend of all indicators emphasizes the effectiveness of the reinforcement of our MRSA control programme. From 2002 to 2004, the trend of the indicator related to the risk of acquisition over time is similar to those of other indicators. Further studies should be useful to assess if risk-adjustment is absolutely necessary when tracking rates within a single institution.

Methicillin-resistant Staphylococcus aureus in an Irish orthopaedic centre: a five-year analysis

This prospective five-year study analyses the impact of methicillin-resistant Staphylococcus aureus (MRSA) on an Irish orthopaedic unit. We identified 318 cases of MRSA, representing 0.76% of all admissions (41,971). A total of 240 (76%) cases were colonised with MRSA, while 120 (37.7%) were infected. Patients were admitted from home (218; 68.6%), nursing homes (72; 22.6%) and other hospitals (28; 8.8%). A total of 115 cases (36.6%) were colonised or infected on admission. Many patients were both colonised and infected at some stage. The length of hospital stay was almost trebled because of the presence of MRSA infection. Encouragingly, overall infection rates have not risen significantly over the five years of the study despite increased prevalence of MRSA. However, the financial burden of MRSA is increasing, highlighting the need for progress in understanding how to control this resistant pathogen more effectively.

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.

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 (e.g., 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.

Aktuelle MRSA-Problematik

Methicillin-resistant Staphylococcus aureus (MRSA) play an important role in hospitals today. Internationally and also within individual countries, its frequency differs considerably. Apart from routine microbiological diagnostics, screening at hospital admission is considered to be of great importance, either to introduce infection control measures as recommended by the Robert Koch Institute, or epidemiologically whether a patient was already colonized at admission. Despite the widespread opinion that patients with MRSA must be isolated in single rooms, no scientific data support that measure in the endemic setting. On the other hand, it is broadly accepted that standard infection control practices, predominantly hand disinfection, are clearly the basic requirement for preventing the transmission of pathogens.

Is tea tree oil effective at eradicating MRSA colonization? A review

In vitro studies show that tea tree oil is capable of killing methicillin-resistant Staphylococcus aureus (MRSA) in a laboratory setting. This review of randomized controlled trials (RCTs) was undertaken to find out whether it is effective at eradicating MRSA colonization compared to standard mupirocin-based regimens in colonized patients. A wide range of databases and internet sources were searched to identify published and unpublished studies. Two RCTs were found that researched the effectiveness of tea tree oil preparations against MRSA. One small RCT (n = 30) showed a large but non-significant improvement at eradicating MRSA compared to traditional treatment, whereas a larger study (n = 224) demonstrated little difference in rates of eradication overall (41% for tea tree and 49% for mupirocin, p = 0.286). However, the larger study found that those with nasal colonization receiving a tea tree regimen were more likely to remain colonized with MRSA in the nose (absolute risk increase 31%, p<0.001). Currently there is insufficient evidence to support the routine use of tea tree oil in clinical practice for eradication of MRSA colonization.

Significant reduction of endemic MRSA acquisition and infection in cardiothoracic patients by means of an enhanced targeted infection control programme

Due to increasing methicillin-resistant Staphylococcus aureus (MRSA) infection in cardiothoracic patients at St Thomas' Hospital, an enhanced infection control programme was introduced in September 2000. It was based on UK national guidelines on the control of MRSA and targeted additional identified risk factors for surgical site infection (SSI). It included recognition of the problem by senior staff and their taking responsibility for it; intensive support, education and advice from the infection control team; improved ward and theatre hygiene; pre-admission, admission and weekly MRSA screening; isolation and clearance treatment; nursing care pathways for MRSA colonized patients; and teicoplanin plus gentamicin surgical prophylaxis. The effectiveness of the programme was assessed by retrospective analysis of computerized patient data for the 16 months before and after the introduction of the programme. There was no significant change in the number of operations or the proportion of patients admitted with MRSA, although nine patients were cleared of carriage before admission. However, there were significant falls in the proportion of patients acquiring MRSA on the ward [38/1036 to 14/921, P=0.003, RR 2.4 (95%CI 1.32-4.42)] and in the rate of bloodstream MRSA infections [12/1075 to 2/956, P=0.014, RR 5.34 (95%CI 1.20-23.78)]. Sternal and leg wound infections both halved (from 28/1075 to 13/956 and 16/1075 to 7/956, respectively) but this did not reach statistical significance. These results demonstrate that an enhanced, targeted infection control programme based on the UK national guidelines, SSI prevention guidelines and local risk assessment can reduce the incidence of nosocomial MRSA acquisition and invasive infection in cardiothoracic patients in the face of continuing endemic risk.

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.