Colonization of Extended-spectrum β-lactamase producing Enterobacterales and meticillin-resistant S. aureus in the intensive care unit at a tertiary hospital in Tanzania: Implications for Infection control and prevention

Background

Multi-drug resistant (MDR) bacteria pose a major global threat to public-health and are of particular concern to hospitalized intensive care unit (ICU) patients. This study aimed at addressing the burden of MDR and the associated factors at admission to ICU.

Methods

This was a cross-sectional study conducted at the ICU of a tertiary hospital in Tanzania. Rectal and anterior nares swabs were collected within 48 hours of ICU admission to screen for extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-PE) and meticillin-resistant Staphylococcus aureus (MRSA), respectively.

Results

The proportion of fecal carriage for ESBL-PE at admission to ICU was 54.54% (95% CI, 47.52–61.39), and nasal carriage for MRSA was 9.32% (95%CI, 5.67–14.93). The nasal MRSA colonization (OR = 1.52) and fecal carriage for ESBL-PE (OR=1.38) were more likely in participants who had received antibiotics before ICU admission than not, but association was not statistically significant. Hospitalization for ≥2 days (OR=1.18) was associated with fecal carriage of ESBL-PE, though not statistically significant. Overall, 66% and 73.5% of patients received antibiotics before and upon admission to ICU, respectively. Ceftriaxone, metronidazole and meropenem were commonly prescribed antibiotics. More than 84% of Enterobacterales were resistant to ciprofloxacin and trimethoprim-sulfamethoxazole, and 2.90% were resistant to meropenem. MRSA isolates showed a high rate of resistance to gentamicin and erythromycin.

Conclusion

MDR bacteria are common in patients admitted to ICU. To reduce the risk associated with MDR, we recommend use of simple screening methods to screen for MDR at ICU admission as part of infection control and prevention.

Methicillin-Resistant Staphylococcus aureus: An Update on Prevention and Control in Acute Care Settings

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of health-care-associated infections. Controversies regarding the effectiveness of various control strategies have contributed to varying approaches to MRSA control. However, new evidence from large-scale studies has emerged, particularly concerning screening and decolonization. Importantly, implementation and outcomes of control measures in practice are not only influenced by scientific evidence, but also economic, administrative, and political factors, as demonstrated by decreasing MRSA rates in a number of countries after concerted and coordinated efforts at a national level. Flexibility to adapt measures based on local epidemiology and resources is essential for successful MRSA control.

Methicillin-Resistant Staphylococcus aureus Infection and Treatment Options

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of infection worldwide, including a wide array of both hospital- and community-acquired infections-most commonly bacteremia, upper and lower respiratory tract infection, skin and soft-tissue infection, osteomyelitis, and septic arthritis. This chapter describes the epidemiology of MRSA infection, its ability to confer antibiotic resistance and produce a wide array of virulence factors, and its pivotal role in human infection, especially cystic fibrosis. It also provides an introduction to the strategies for treatment of both chronic and acute MRSA infections.

Prevention and Control of Methicillin-Resistant Staphylococcus aureus in Acute Care Settings

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of health care-associated infections worldwide. Controversies with regard to the effectiveness of various MRSA control strategies have contributed to varying approaches to the control of this pathogen in different settings. However, new evidence from large-scale studies has emerged, particularly with regards to MRSA screening and decolonization strategies, which will inform future control practices. The implementation as well as outcomes of control measures in the real world is not only influenced by scientific evidence but also depends on economic, administrative, governmental, and political influences.

Methicillin-resistant Staphylococcus aureus (MRSA) nasal real-time PCR: a predictive tool for contamination of the hospital environment

OBJECTIVE We sought to determine whether the bacterial burden in the nares, as determined by the cycle threshold (CT) value from real-time MRSA PCR, is predictive of environmental contamination with MRSA. METHODS Patients identified as MRSA nasal carriers per hospital protocol were enrolled within 72 hours of room admission. Patients were excluded if (1) nasal mupirocin or chlorhexidine body wash was used within the past month or (2) an active MRSA infection was suspected. Four environmental sites, 6 body sites and a wound, if present, were cultured with premoistened swabs. All nasal swabs were submitted for both a quantitative culture and real-time PCR (Roche Lightcycler, Indianapolis, IN). RESULTS At study enrollment, 82 patients had a positive MRSA-PCR. A negative correlation of moderate strength was observed between the CT value and the number of MRSA colonies in the nares (r=-0.61; P<0.01). Current antibiotic use was associated with lower levels of MRSA nasal colonization (CT value, 30.2 vs 27.7; P<0.01). Patients with concomitant environmental contamination had a higher median log MRSA nares count (3.9 vs 2.5, P=0.01) and lower CT values (28.0 vs 30.2; P<0.01). However, a ROC curve was unable to identify a threshold MRSA nares count that reliably excluded environmental contamination. CONCLUSIONS Patients with a higher burden of MRSA in their nares, based on the CT value, were more likely to contaminate their environment with MRSA. However, contamination of the environment cannot be predicted solely by the degree of MRSA nasal colonization.

Long-Term Control of Endemic Hospital-Wide Methicillin-ResistantStaphylococcus aureus(MRSA): The Impact of Targeted Active Surveillance for MRSA in Patients and Healthcare Workers

Objective.

To evaluate the long-term impact of successive interventions on rates of methicillin-resistantStaphylococcus aureus(MRSA) colonization or infection and MRSA bacteremia in an endemic hospital-wide situation.

Design.

Quasi-experimental, interrupted time-series analysis. The impact of the interventions was analyzed by use of segmented regression. Representative MRSA isolates were typed by use of pulsed-field gel electrophoresis.

Setting.

A 950-bed teaching hospital in Seville, Spain.

Patients.

All patients admitted to the hospital during the period from 1995 through 2008.

Methods.

Three successive interventions were studied: (1) contact precautions, with no active surveillance for MRSA; (2) targeted active surveillance for MRSA in patients and healthcare workers in specific wards, prioritized according to clinical epidemiology data; and (3) targeted active surveillance for MRSA in patients admitted from other medical centers.

Results.

Neither the preintervention rate of MRSA colonization or infection (0.56 cases per 1,000 patient-days [95% confidence interval {CI}, 0.49-0.62 cases per 1,000 patient-days]) nor the slope for the rate of MRSA colonization or infection changed significantly after the first intervention. The rate decreased significantly to 0.28 cases per 1,000 patient-days (95% CI, 0.17-0.40 cases per 1,000 patient-days) after the second intervention and to 0.07 cases per 1,000 patient-days (95% CI, 0.06-0.08 cases per 1,000 patient-days) after the third intervention, and the rate remained at a similar level for 8 years. The MRSA bacteremia rate decreased by 80%, whereas the rate of bacteremia due to methicillin-susceptibleS. aureusdid not change. Eighty-three percent of the MRSA isolates identified were clonally related. All MRSA isolates obtained from healthcare workers were clonally related to those recovered from patients who were in their care.

Conclusion.

Our data indicate that long-term control of endemic MRSA is feasible in tertiary care centers. The use of targeted active surveillance for MRSA in patients and healthcare workers in specific wards (identified by means of analysis of clinical epidemiology data) and the use of decolonization were key to the success of the program.

Systematic literature analysis and review of targeted preventive measures to limit healthcare-associated infections by meticillin-resistant Staphylococcus aureus

Meticillin-resistant Staphylococcus aureus (MRSA) is a major cause of healthcare-associated infections in Europe. Many examples have demonstrated that the spread of MRSA within healthcare settings can be reduced by targeted infection control measures. The aim of this systematic literature analysis and review was to summarise the evidence for the use of bacterial cultures for active surveillance the benefit of rapid screening tests, as well as the use of decolonisation therapies and different types of isolation measures. We included 83 studies published between 2000 and 2012. Although the studies reported good evidence supporting the role of active surveillance followed by decolonisation therapy, the effectiveness of single-room isolation was mostly shown in non-controlled studies, which should inspire further research regarding this issue. Overall, this review highlighted that when planning the implementation of preventive interventions, there is a need to consider the prevalence of MRSA, the incidence of infections, the competing effect of standard control measures (e.g. hand hygiene) and the likelihood of transmission in the respective settings of implementation.

A model-based analysis: what potential could there be for a S. aureus vaccine in a hospital setting on top of other preventative measures?

BACKGROUND

Over the past decade, there has been sustained interest and efforts to develop a S. aureus vaccine. There is a need to better evaluate the potential public health impact of S. aureus vaccination, particularly given that preventative measures exist to reduce infection. To our knowledge, there is no previous work to assess the potential of a S. aureus vaccine to yield additional MRSA infection reduction in a hospital setting, on top of other preventative measures that already proved efficient.

METHODS

The main objectives were to propose a versatile simulation framework for assessing potential added benefits of a hypothetical S. Aureus vaccine in conjunction with other preventative measures, and to illustrate possibilities in a given hospital setting. To this end, we employed a recently published dynamic transmission modelling framework that we further adapted and expanded to include a hypothetical S. aureus vaccination component in order to estimate potential benefits of vaccinating patients prior to hospital admission.

RESULTS

Model-based projections indicate that even with other hygiene prevention measures in place, vaccination of patients prior to hospital admission has the potential to provide additional reduction of MRSA infection. Vaccine coverage and vaccine efficacy are key factors that would ultimately impact the magnitude of this reduction. For example, in an average case scenario with 50% decolonization, 50% screening and 50% hygiene compliance level in place, S. aureus vaccination with 25% vaccine coverage, 75% vaccine efficacy against infection, and 0% vaccine efficacy against colonization, may lead to 12% model-projected additional reduction in MRSA infection prevalence due to vaccination, while this reduction could reach 37% for vaccination with 75% vaccine coverage and 75% vaccine efficacy against infection in the same average case scenario.

CONCLUSIONS

S. aureus vaccination could potentially provide additional reduction of MRSA infection in a hospital setting, on top of reductions from hygiene prevention measures. The magnitude of such additional reductions can vary significantly depending on the level of hygiene prevention measures in place, as well as key vaccine factors such as coverage and efficacy. Identifying appropriate combinations of preventative measures may lead to optimal strategies to effectively reduce MRSA infection in hospitals.

Screening for methicillin-resistant Staphylococcus aureus: a comparative effectiveness review

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of health care-associated infections. Although the evidence in support of MRSA screening has been promising, a number of questions remain about the effectiveness of active surveillance.

METHODS

We searched the literature for studies that examined MRSA acquisition, MRSA infection, morbidity, mortality, harms of screening, and resource utilization when screening for MRSA carriage was compared with no screening or with targeted screening. Because of heterogeneity of the data and weaknesses in study design, meta-analysis was not performed. Strength of evidence (SOE) was determined using the system developed by the Grading of Recommendations Assessment, Development and Evaluation Working Group.

RESULTS

One randomized controlled trial and 47 quasi-experimental studies met our inclusion criteria. We focused on the 14 studies that addressed health care-associated outcomes and that attempted to control for confounding and/or secular trends, because those studies had the potential to support causal inferences. With universal screening for MRSA carriage compared with no screening, 2 large quasi-experimental studies found reductions in health care-associated MRSA infection. The SOE for this finding is low. For each of the other screening strategies evaluated, this review found insufficient evidence to determine the comparative effectiveness of screening.

CONCLUSIONS

Although there is low SOE that universal screening of hospital patients decreases MRSA infection, there is insufficient evidence to determine the consequences of universal screening or the effectiveness of other screening strategies.

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

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

MRSA nasal colonization in children: prevalence meta-analysis, review of risk factors and molecular genetics

BACKGROUND

We report a meta-analysis of methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization prevalence in children and a review of the risk factors as well as molecular genetic characterization.

METHODS

All relevant studies reporting prevalence data on MRSA nasal colonization in children published between January 2000 and August 2010 were retrieved from the MEDLINE database and analyzed.

RESULTS

After screening 544 studies, 50 studies were included. We obtained an estimate of MRSA prevalence of 2.7% (95% confidence interval [CI]: 2.2-3.1); of 5.2% (95% CI: 3.1-7.3) in children with underlying conditions and of 2.3% (95% CI: 1.8-2.7) in healthy children; 5.4% (95% CI: 3.1-7.7) in children recruited in hospitals and 3% (95% CI: 2.4-3.6) in children recruited in the community. Staphylococcal cassette chromosome mec type IV is the most diffused cassette globally.

CONCLUSION

The hospital remains the environment where the microorganism circulates most. Children with underlying conditions could act as vectors of microorganisms between the hospital and the community. MRSA prevention strategies should be tailored to each specific institution, taking into account the nosocomial prevalence of MRSA nasal colonization and infections, and the prevalence of nasal colonization in the community that refers to the specific health care center.

Infection prevention in a connected world: the case for a regional approach

Results from microbiological and epidemiological investigations, as well as mathematical modelling, show that the transmission dynamics of nosocomial pathogens, especially of multiple antibiotic-resistant bacteria, is not exclusively amenable to single-hospital infection prevention measures. Crucially, their extent of spread depends on the structure of an underlying "healthcare network", as determined by inter-institutional referrals of patients. The current trend towards centralized healthcare systems favours the spread of hospital-associated pathogens, and must be addressed by coordinated regional or national approaches to infection prevention in order to maintain patient safety. Here we review recent advances that support this hypothesis, and propose a "next-generation" network-approach to hospital infection prevention and control.

Transmission of endemic ST22-MRSA-IV on four acute hospital wards investigated using a combination of spa, dru and pulsed-field gel electrophoresis typing

The transmission of meticillin-resistant Staphylococcus aureus (MRSA) between individual patients is difficult to track in institutions where MRSA is endemic. We investigated the transmission of MRSA where ST22-MRSA-IV is endemic on four wards using demographic data, patient and environmental screening, and molecular typing of isolates. A total of 939 patients were screened, 636 within 72 h of admission (on admission) and 303 >72 h after admission, and 1,252 environmental samples were obtained. Isolates were typed by spa, dru and pulsed-field gel electrophoresis (PFGE) typing. A composite dendrogram generated from the three sets of typing data was used to divide isolates into 'dendrogram groups' (DGs). Ten percent of patients (92/939) were MRSA-positive; 7 % (44/636) on admission and 16 % (48/303) >72 h after admission (p = 0.0007). MRSA was recovered from 5 % of environmental specimens (65/1,252). Most isolates from patients (97 %, 85/88) and the environment (97 %, 63/65) exhibited the ST22-MRSA-IV genotype. Four DGs (DG1, DG4, DG16 and DG17) accounted for 58 % of ST22-MRSA-IV isolates from patients. Epidemiological evidence suggested cross-transmission among 44/92 patients (48 %) but molecular typing confirmed probable cross-transmission in only 11 instances (13 %, 11/88), with the majority of cross-transmission (64 %; 7/11) occurring on one ward. In the setting of highly clonal endemic MRSA, the combination of local epidemiology, PFGE, spa and dru typing provided valuable insights into MRSA transmission.

Evaluation of screening risk and nonrisk patients for methicillin-resistant Staphylococcus aureus on admission in an acute care hospital

BACKGROUND

Screening for methicillin-resistant Staphylocccus aureus (MRSA) is advocated as part of control measures, but screening all patients on admission to hospital may not be cost-effective.

OBJECTIVE

Our objective was to evaluate the additional yield of screening all patients on admission compared with only patients with risk factors and to assess cost aspects.

METHODS

A prospective, nonrandomized observational study of screening nonrisk patients ≤72 hours of admission compared with only screening patients with risk factors over 3 years in a tertiary referral hospital was conducted. We also assessed the costs of screening both groups.

RESULTS

A total of 48 of 892 (5%) patients was MRSA positive; 28 of 314 (9%) during year 1, 12 of 257 (5%) during year 2, and 8 of 321 (2%) during year 3. There were significantly fewer MRSA-positive patients among nonrisk compared with MRSA-risk patients: 4 of 340 (1%) versus 44 of 552 (8%), P ≤ .0001, respectively. However, screening nonrisk patients increased the number of screening samples by 62% with a proportionate increase in the costs of screening. A backward stepwise logistic regression model identified age > 70 years, diagnosis of chronic pulmonary disease, previous MRSA infection, and admission to hospital during the previous 18 months as the most important independent predictors to discriminate between MRSA-positive and MRSA-negative patients on admission (94.3% accuracy, P < .001).

CONCLUSION

Screening patients without risk factors increased the number of screenings and costs but resulted in few additional cases being detected. In a hospital where MRSA is endemic, targeted screening of at-risk patients on admission remains the most efficient strategy for the early identification of MRSA-positive patients.

Review of indicators for cross-sectoral optimization of nosocomial infection prophylaxis - a perspective from structurally- and process-oriented hygiene

In the care of patients, the prevention of nosocomial infections is crucial. For it to be successful, cross-sectoral, interface-oriented hygiene quality management is necessary. The goal is to apply the HACCP (Hazard Assessment and Critical Control Points) concept to hospital hygiene, in order to create a multi-dimensional hygiene control system based on hygiene indicators that will overcome the limitations of a procedurally non-integrated and non-cross-sectoral view of hygiene.

Three critical risk dimensions can be identified for the implementation of three-dimensional quality control of hygiene in clinical routine: the constitution of the person concerned, the surrounding physical structures and technical equipment, and the medical procedures. In these dimensions, the establishment of indicators and threshold values enables a comprehensive assessment of hygiene quality. Thus, the cross-sectoral evaluation of the quality of structure, processes and results is decisive for the success of integrated infection prophylaxis.

This study lays the foundation for hygiene indicator requirements and develops initial concepts for evaluating quality management in hygiene.

National prevalence of methicillin-resistant Staphylococcus aureus in inpatients at United States health care facilities, 2010

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) remains one of the most prevalent multidrug-resistant organisms causing health care-associated infections. Limited data are available about how the prevalence of MRSA has changed over the past several years and what MRSA prevention practices have been implemented since the 2006 Association for Professionals in Infection Control and Epidemiology, Inc, MRSA survey.

METHODS

We conducted a national prevalence survey of MRSA colonization or infection in inpatients at US health care facilities. The survey was developed, received institutional review board approval, and then was distributed to all US Association for Professionals in Infection Control and Epidemiology, Inc, members. Members were asked to complete the survey on 1 day during the period August 1 to December 30, 2010, reporting the number of inpatients with MRSA infection or colonization and facility- and patient-specific information.

RESULTS

Personnel at 590 facilities indicated a state and responded to the survey. All states were represented, except for Alaska and Washington, DC (mean, 12 facilities per state; range, 1-38). Respondents reported 4,476 MRSA-colonized/infected patients in 67,412 inpatients; the overall MRSA prevalence rate was 66.4 per 1,000 inpatients (25.3 infections and 41.1 colonizations per 1,000 inpatients). Active surveillance testing was conducted by 75.7% of the respondents; 39.6% used nonselective media, 37.2% used selective media, and 23.3% used polymerase chain reaction. Detailed data were provided on 3,176 MRSA-colonized/infected patients. Of those in whom colonization/infection status was reported (1,908/3,086 [61.8%] were MRSA colonized and 1,778/3,086 [38.2%] were MRSA infected), most MRSA-colonized or infected patients (78.3%) were detected within 48 hours of admission; the most common site of infection was skin and soft tissue (42.9%); and, using the Centers for Disease Control and Prevention's definitions, approximately 50% would be classified as health care-associated infections.

CONCLUSION

Our survey documents that the MRSA prevalence in 2010 is higher than that reported in our 2006 survey. However, the majority of facilities currently are performing active surveillance testing, and, compared with 2006, the rate of MRSA infection has decreased while the rate of MRSA colonization has increased. In addition, compared with 2006, the proportion of MRSA strains recovered from MRSA-colonized/infected patients that are health care-associated strains has deceased, and community-associated strains have increased.

Costs and benefits of rapid screening of methicillin-resistant Staphylococcus aureus carriage in intensive care units: a prospective multicenter study

INTRODUCTION

Pre-emptive isolation of suspected methicillin-resistant Staphylococcus aureus (MRSA) carriers is a cornerstone of successful MRSA control policies. Implementation of such strategies is hampered when using conventional cultures with diagnostic delays of three to five days, as many non-carriers remain unnecessarily isolated. Rapid diagnostic testing (RDT) reduces the amount of unnecessary isolation days, but costs and benefits have not been accurately determined in intensive care units (ICUs).

METHODS

Embedded in a multi-center hospital-wide study in 12 Dutch hospitals we quantified cost per isolation day avoided using RDT for MRSA, added to conventional cultures, in ICUs. BD GeneOhm™ MRSA PCR (IDI) and Xpert MRSA (GeneXpert) were subsequently used during 17 and 14 months, and their test characteristics were calculated with conventional culture results as reference. We calculated the number of pre-emptive isolation days avoided and incremental costs of adding RDT.

RESULTS

A total of 163 patients at risk for MRSA carriage were screened and MRSA prevalence was 3.1% (n=5). Duration of isolation was 27.6 and 21.4 hours with IDI and GeneXpert, respectively, and would have been 96.0 hours when based on conventional cultures. The negative predictive value was 100% for both tests. Numbers of isolation days were reduced by 44.3% with PCR-based screening at the additional costs of €327.84 (IDI) and €252.14 (GeneXpert) per patient screened. Costs per isolation day avoided were €136.04 (IDI) and €121.76 (GeneXpert).

CONCLUSIONS

In a low endemic setting for MRSA, RDT safely reduced the number of unnecessary isolation days on ICUs by 44%, at the costs of €121.76 to €136.04 per isolation day avoided.

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.

Methicillin-resistant Staphylococcus aureus nasal colonization is a poor predictor of intensive care unit-acquired methicillin-resistant Staphylococcus aureus infections requiring antibiotic treatment

OBJECTIVE

To test whether intensive care unit (ICU) nasal screening for methicillin-resistant Staphylococcus aureus (MRSA) predicts the presence or absence of MRSA infections requiring antimicrobial treatment.

DESIGN

A prospective cohort study.

SETTING

Medical ICU at Barnes-Jewish Hospital, a 1252-bed urban teaching hospital.

PATIENTS

Seven hundred forty-nine consecutive patients admitted to the medical ICU over a 7-mo period (November 2007 through June 2008).

INTERVENTIONS

Nasal swabs were obtained at ICU admission and weekly thereafter for MRSA detection by using polymerase chain reaction. All subjects were followed for the development of MRSA infection during their ICU stay.

MEASUREMENTS AND MAIN RESULTS

One hundred sixty-four (21.9%) patients had positive nasal colonization with MRSA at the time of ICU admission. The predictive accuracy of MRSA nasal colonization for ICU-acquired MRSA infections, either lower respiratory tract infection or bloodstream infection, was poor (lower respiratory tract infection: sensitivity, 24.2%; specificity, 78.5%; positive predictive value, 17.7%; and negative predictive value, 84.4%; and bloodstream infection: sensitivity, 23.1%; specificity, 78.2%; positive predictive value, 11.0%; and negative predictive value, 89.7%). Addition of nasal-colonization results obtained during the ICU stay did not appreciably change the predictive accuracy of this test for identification of subsequent lower respiratory tract infections and bloodstream infections attributed to MRSA requiring antimicrobial treatment.

CONCLUSIONS

In this analysis, nasal colonization with MRSA was found to be a poor predictor for the subsequent occurrence of MRSA lower respiratory tract infections and MRSA bloodstream infections requiring antimicrobial treatment. Clinicians should be cautious in using the results of nasal-colonization testing to determine the need for MRSA treatment among patients with ICU-acquired infections.

Long-term persistence of MRSA in re-admitted patients

BACKGROUND

A better knowledge of methicillin-resistant Staphylococcus aureus (MRSA) persistence in hospitalised patients may impact on specific prevention strategies. We have investigated the persistence of MRSA-carriage in patients admitted and re-admitted to a university hospital.

PATIENTS AND METHODS

Between January 2002 and October 2005 all MRSA-positive patients admitted to the university hospital of Hannover Medical School were assessed at first admission and all subsequent re-admissions. Patients re-admitted at least once were analysed for the persistence or loss of MRSA. The association of possible factors influencing the persistence of MRSA colonisation or infection (age group, gender, decolonisation therapy during first hospital stay due to MRSA positivity and colonisation of different anatomical sites) was analysed using univariate, multivariate and time-dependent analyses.

RESULTS

A total of 1,032 patients who had tested positive at least once for MRSA were admitted to our hospital during the study period, accounting for 2,038 admissions. Of these patients, 403 (39.1%) were admitted more than once (from two times to 21 times), and 238 (59.1%) of the re-admitted patients remained MRSA positive during all subsequent admissions. Fifty-five (13.6%) patients tested MRSA negative at their last admission, and 61 (15.1%) tested MRSA negative at at least two consecutive admissions. In 27 (6.7%) patients, the MRSA status differed more than once between subsequent admissions. Overall, the half-life time (HLT) of MRSA persistence was 549 days, with the duration of persistence dependent on the colonisation of different anatomical sites (HLT only wounds 117 days; HLT mouth, throat, bronchial secretions 627 days; HLT nose, wounds and other body sites 801 days; p < 0.01) and was prolonged if more than one body site was MRSA-positive (HR 2.18, 95% confidence interval 1.52-3.15).

CONCLUSION

A detailed knowledge of the dynamics of the loss of MRSA infection could result in a reduction of the incidence of MRSA in the future. Multiple anatomical site carriage of MRSA appeared to predict a prolonged persistence in our cohort of patients re-admitted to a university hospital.

Evaluation of multiple-locus variable-number tandem-repeat analysis for typing a polyclonal hospital-acquired methicillin-resistant Staphylococcus aureus population in an area where such infections are endemic

Multiple-locus variable-number tandem-repeat analysis (MLVA) was performed with 292 methicillin-resistant Staphylococcus aureus (MRSA) isolates previously characterized by pulsed-field gel electrophoresis, multilocus sequence typing, and staphylococcal cassette chromosome mec typing. Quantitative correspondence analyses showed the best correlation between data when an >or=80% cutoff was applied to MLVA. We confirmed the validity of MLVA for identification of related strains in a polyclonal MRSA population.

Can 'search and destroy' reduce nosocomial methicillin-resistant Staphylococcus aureus in an Irish hospital?

In Ireland, the Department of Health and Children recommends admission screening of patients at increased risk of methicillin-resistant Staphylococcus aureus (MRSA), isolation of these patients until proven negative, and eradication of any MRSA identified. These actions form the basis of a programme called 'search and destroy' that has successfully reduced MRSA in Scandinavia. There is, however, very little information published on the use of search and destroy in Ireland. This study was carried out using a quantitative, quasi-experimental design in the form of an interventional cohort study. The effect of reducing the turnaround time for MRSA results (2007) and the introduction of pre-emptive isolation (2008) was examined in a hospital with an established admission screening programme for MRSA. Rates of MRSA infection and colonisation were monitored post-intervention and compared to baseline rates prior to the intervention (2005-2006). Rates of hospital-acquired (nosocomial) MRSA infections and colonisation fell in both 2007 and 2008. However, due to the quasi-experimental design of the study and the low endemic level of MRSA in the hospital, a causal link could not be established.

Implementing the MRSA recommendations made by the Commission for Hospital Hygiene and Infection Prevention (KRINKO) of 1999 - current considerations by the DGKH Management Board

In Germany, recommendations on dealing with patients who are colonised with methicillin-resistant S. aureus (MRSA) for the inpatient sector have been published in 1999 by the Commission for Hospital Hygiene and Infection Prevention (KRINKO). Some challenges arise with regard to the practical implementation of the KRINKO recommendations. These challenges do not principally question the benefit of the recommendations but have come into criticism from users. In this commentary the German Society for Hospital Hygiene (DGKH) discusses some controversial issues and adds suggestions for unresolved problems regarding the infection control management of MRSA in healthcare settings.

Multiple-locus variable-number tandem-repeat analysis of meticillin-resistant Staphylococcus aureus discriminates within USA pulsed-field gel electrophoresis types

Many isolates of meticillin-resistant Staphylococcus aureus (MRSA) are indistinguishable when compared using the standard pulsed-field gel electrophoresis (PFGE) typing method. This may present a problem when investigating local outbreaks of MRSA transmission in a healthcare setting. It also impedes investigation of the widely disseminated community-acquired MRSA (USA 300-0114) in the inpatient setting, which is displacing other traditional hospital-acquired PFGE types. Combination of methods, including multiple-locus sequence typing (MLST), spa typing and staphylococcal cassette chromosome mec (SCCmec) typing, have been used with, or in place of, PFGE to characterise MRSA for epidemiological purposes. These methods are technically challenging, time-consuming and expensive and are rarely feasible except in large laboratories in tertiary care medical centres. Another method, which is simpler and with faster turnaround time, is multiple-locus variable-number tandem-repeat analysis (MLVA). We investigated the utility of MLVA to distinguish common PFGE types. The results suggest that MLVA can be used to identify unrelated strains with identical PFGE patterns or confirm close genetic composition of linked isolates. MLVA could potentially be used in conjunction with PFGE to validate relationships, but further prospective evaluation of these relationships will be required in order to define the proper role, if any, for use of this method in hospital epidemiology.