Nosocomial Meticillin-resistant Staphylococcus Aureus Research Articles

MRSA transmission between horses and vets: who's doing the infecting?

METICILLIN-resistant Staphylococcus aureus (MRSA) is a major health problem in people. About 30 per cent of the general population are nasal carriers of Staphylococcus aureus , and only a small...

Reduction of the nosocomial meticillin-resistant Staphylococcus aureus incidence density by a region-wide search and follow-strategy in forty German hospitals of the EUREGIO, 2009 to 2011

Meticillin-resistant Staphylococcus aureus (MRSA) disseminates between hospitals serving one patient catchment area. Successful prevention and control requires concerted efforts and regional surveillance. Forty hospitals located in the German EUREGIO have established a network for combating MRSA. In 2007 they agreed upon a synchronised strategy for screening of risk patients and a standard for transmissionbased precautions (search and follow). The same year, the hospitals started synchronised MRSA prevention and annually reporting MRSA-data to the public health authorities. The median rate of screening cultures per 100 patients admitted increased from 4.38 in 2007 to 34.4 in 2011 (p<0.0001). Between 2007 and 2011, the overall incidence density of MRSA (0.87 MRSA cases/1,000 patient days vs 1.54; p<0.0001) increased significantly. In contrast, both the incidence density of nosocomial MRSA cases (0.13 nosocomial MRSA cases/1,000 patient days in 2009 vs 0.08 in 2011; p=0.0084) and the MRSA-days-associated nosocomial MRSA rate (5.51 nosocomial MRSA cases/1,000 MRSA days in 2009 vs 3.80 in 2011; p=0.0437) decreased significantly after the second year of the project. We documented adherence to the regional screening strategy resulting in improved detection of MRSA carriers at admission. Subsequently, after two years the nosocomial MRSA-incidence density was reduced. Regional surveillance data, annually provided as benchmarking to the regional hospitals and public health authorities, indicated successful prevention.

Associations between nosocomial meticillin-resistant Staphylococcus aureus and nosocomial Clostridium difficile-associated diarrhoea in 89 German hospitals

Clostridium difficile is mainly considered as a hospital-acquired pathogen causing diarrhoea in healthcare settings. To quantify and compare the incidence density of hospital-acquired meticillin-resistant Staphylococcus aureus (MRSA) and C.difficile-associated infection (CDI) in a network of German hospitals; also to assess whether there is an association between nosocomial MRSA and nosocomial CDI. Acute hospitals reported data on the number of patients, patient-days and MRSA and/or CDI cases to the German nosocomial infection surveillance system (KISS). Cases were classified as nosocomial or imported. Nosocomial incidences and incidence densities (per 1000 patient-days) of MRSA and CDI were calculated by Spearman correlation index. In 2010, a total of 89 hospitals reported hospital-wide MRSA and CDI cases. The analysis included 1,536,031 patients, 11,138,496 patient-days, 5183 nosocomial CDI cases and 2233 nosocomial MRSA cases. The pooled incidence density of nosocomial CDI was 0.47, more than two-fold higher than that of nosocomial MRSA (0.20). Correlation of nosocomial incidences of MRSA and CDI was statistically significant [correlation coefficient (CC) of 0.515]. Correlation of incidence densities was likewise significant with a CC of 0.484. The incidence of nosocomial CDI was twice as high as nosocomial MRSA incidence among our database and with the definitions used. High nosocomial MRSA or CDI cases might be indicators for deficits in infection control and/or selection pressure of antibiotics.

Clinical and molecular epidemiology of meticillin-resistant Staphylococcus aureus causing bacteraemia in Southern Spain

Some molecular features of meticillin-resistant Staphylococcus aureus (MRSA) isolates causing invasive infections have been shown to have clinical implications. There is a need to monitor the situation using a combination of molecular and clinical data because, although MRSA clones tend to predominate over wide geographical areas, clonal shifts may take place. To study the epidemiological features and perform molecular characterization of a retrospective cohort of 98 cases of nosocomial and healthcare-associated MRSA bacteraemia in 10 hospitals in Andalusia, Spain. Relatedness of isolates was investigated using pulsed-field gel electrophoresis (PFGE), S.aureus protein A (spa) typing and clonal complex (CC) assignment. Staphylococcal chromosomal cassette mec (SCCmec) type and accessory gene regulator (agr) group were studied by polymerase chain reaction. agr function was assessed. Most isolates were CC5, SCCmec type IV and agr group II. The most common spa type was t067. Six major clusters were identified by PFGE. Six small clusters of epidemiologically related cases sharing isolates from the same PFGE subtype were identified. Five percent of isolates had a vancomycin minimum inhibitory concentration (MIC) of 2μg/mL on broth microdilution, although 44% had an MIC >1μg/mL on E-test. Variables independently associated with MIC >1mg/L on E-test were surgery during present admission and Charlson index ≥2. A specific CC that has been predominant in Spain over the last decade caused most of the cases in this study. PFGE was more discriminatory than spa typing in showing clusters of epidemiologically related cases. Some patient features were associated with vancomycin MIC >1mg/L on E-test.

Multistate modelling to estimate the excess length of stay associated with meticillin-resistant Staphylococcus aureus colonisation and infection in surgical patients

Currently available evidence on the excess length of stay (LOS) associated with nosocomial infections is limited by methodology, including time-dependent bias. To determine the excess LOS associated with nosocomial meticillin-resistant Staphylococcus aureus (MRSA) infection and colonisation, 797 MRSA-colonised, 167 MRSA-infected and 13,640 MRSA-negative surgical patients were included in a multistate model. The occurrence of MRSA infection or colonisation was the time-dependent exposure, and discharge or death was the study endpoint. The excess LOS was extracted by computing the Aalen-Johansen estimator of the matrix of transition probabilities. Multivariate Cox regression analysis was used to assess the independent effect of MRSA on excess LOS. MRSA infection prolonged LOS by 14.5 [95% confidence interval (CI): 7.8, 21.3] days compared to uninfected patients, and by 5.9 (95% CI: 0.1, 11.7) days compared to patients only colonised by MRSA. The hazard of discharge was reduced by nosocomial MRSA infection both with respect to MRSA-free patients and MRSA carriers [adjusted hazard ratio (HR): 0.69; 95% CI: 0.59, 0.81; and HR: 0.79; 95% CI: 0.65, 0.95, respectively]. MRSA carriage alone did not decrease the hazard of discharge after adjustment for confounding (HR: 1.00; 95% CI: 0.93, 1.07). Multistate modelling is a promising statistical method to evaluate the health-economic impact of nosocomial antibiotic-resistant infections.

Costs of nosocomial pneumonia caused by meticillin-resistant Staphylococcus aureus

Nosocomial infections with meticillin-resistant Staphylococcus aureus (MRSA) lead to increased health and economic costs. The purpose of this study was to determine costs fornosocomial MRSA pneumonia compared with meticillin-susceptible S. aureus (MSSA) pneumonia. A case-control study was conducted with patients who acquired nosocomial pneumoniawith either MRSA or MSSA between January 2005 and December 2007. Patients were matched for age, severity of underlying disease, stay on intensive care units and non-intensive care units, admission and discharge within the same year, and in-hospital stay at least as long as that of cases before MRSA pneumonia. Our analysis includes 82 patients (41 cases, 41 controls). The overall costs for patients with nosocomial MRSA pneumonia were significantly higher than for patients with MSSA pneumonia (€60,684 vs €38,731; P=0.01). The attributable costs for MRSA pneumonia per patient were €17,282 (P<0.001). The financial loss was higher for patients with MRSA pneumonia than for patients with MSSA pneumonia (€11,704 vs €2,662; P=0.002). More cases died than controls while in the hospital (13 vs 1 death, P<0.001). Hospital personnel should be aware of the attributable costs of MRSA pneumonia, and should implement control measures to prevent MRSA transmission.

Epidemiology meets econometrics: using time-series analysis to observe the impact of bed occupancy rates on the spread of multidrug-resistant bacteria

Two multivariate time-series analyses were carried out to identify the impact of bed occupancy rates, turnover intervals and the average length of hospital stay on the spread of multidrug-resistant bacteria in a teaching hospital. Epidemiological data on the incidences of meticillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase (ESBL)-producing bacteria were collected. Time-series of bed occupancy rates, turnover intervals and the average length of stay were tested for inclusion in the models as independent variables. Incidence was defined as nosocomial cases per 1000 patient-days. This included all patients infected or colonised with MRSA/ESBL more than 48h after admission. Between January 2003 and July 2008, a mean incidence of 0.15 nosocomial MRSA cases was identified. ESBL was not included in the surveillance until January 2005. Between January 2005 and July 2008 the mean incidence of nosocomial ESBL was also 0.15 cases per 1000 patient-days. The two multivariate models demonstrate a temporal relationship between bed occupancy rates in general wards and the incidence of nosocomial MRSA and ESBL. Similarly, the temporal relationship between the monthly average length of stay in intensive care units (ICUs) and the incidence of nosocomial MRSA and ESBL was demonstrated. Overcrowding in general wards and long periods of ICU stay were identified as factors influencing the spread of multidrug-resistant bacteria in hospital settings.

Impact of active surveillance on meticillin-resistant Staphylococcus aureus transmission and hospital resource utilisation

The utility of active surveillance cultures (ASCs) for meticillin-resistant Staphylococcus aureus (MRSA) has been a controversial aspect of infection prevention. This prospective cohort study analyses the effect of ASCs for MRSA on hospital-acquired infections in a tertiary care hospital (hospital 1) and a community-based hospital (hospital 2). Both hospitals have high MRSA prevalence and are part of a large healthcare system in southeastern Michigan. Hospital-acquired infections in the intensive care unit (ICU) and in the rest of the hospital were compared before and after the implementation of ASCs in the ICUs. Patients in hospital 1 with evidence of MRSA colonisation from ASCs were placed in contact isolation during their stay in the ICU; patients from hospital 2 remained in contact isolation throughout their hospital stay. Prevalence of MRSA colonisation on admission to the ICU was 23% and 13% in hospitals 1 and 2, respectively. Average incidence of new colonisation during the study period was 1.85 per 1000 patient-days and 3.47 per 1000 patient-days in hospitals 1 and 2, respectively. A decrease in ventilator-associated pneumonia (VAP) occurred in both hospitals, whereas decrease in hospital-wide nosocomial MRSA infection was demonstrated only in hospital 2. We conclude that, in addition to standard infection prevention initiatives, ASC with contact precautions can be effective in reducing the incidence of VAP and nosocomial MRSA infection in healthcare communities with endemic MRSA.

Increased mortality among elderly patients with meticillin-resistant Staphylococcus aureus bacteraemia

Despite the high prevalence of meticillin-resistant Staphylococcus aureus (MRSA) infections among the elderly, outcomes of nosocomial MRSA bloodstream infections (BSI) for this patient population have not been fully examined. We performed a case-control study to compare outcomes of hospital-acquired MRSA BSI among patients >/=65 years of age (cases) with those younger than 65 years of age (controls). In a 430-bed tertiary-care teaching hospital, 100 hospitalized patients >/=18 years of age with S. aureus BSI were included in the study. Measurements obtained were: comorbidities, severity of illness at presentation, antibiotic therapy, haematogenous complications and mortality. Overall mortality was significantly higher among cases than controls [36% vs 12%; odds ratio (OR) 4.1, 95% confidence interval (CI) 1.4-14, P<0.01]. A pulmonary source was identified more frequently among elderly patients compared with younger controls (34% vs 16%; OR 2.7, 95%CI 1.1-8.1, P=0.04). On logistic regression, the following variables were independently associated with MRSA BSI among elderly patients: admission to a medical ward (OR 3.1, 95%CI 1.3-7.6, P=0.02), non-central-venous-catheter-related BSI (OR 3, 95%CI 1.2-7.6, P=0.02) and death (OR 3.7, 95%CI 1.3-11, P=0.02). Among patients who received vancomycin, more cases were treated with a reduced dose of vancomycin due to renal insufficiency compared with controls (64% vs 31%; OR 4, 95%CI 2-9, P=0.01). These data suggest that MRSA BSI is associated with significant mortality among the elderly population. Preventing MRSA acquisition among this patient population is of paramount importance.