Carolina Fankhauser

Universal screening for methicillin-resistant Staphylococcus aureus at hospital admission and nosocomial infection in surgical patients.

CONTEXT Experts and policy makers have repeatedly called for universal screening at hospital admission to reduce nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection. OBJECTIVE To determine the effect of an early MRSA detection strategy on nosocomial MRSA infection rates in surgical patients. DESIGN, SETTING, AND PATIENTS Prospective, interventional cohort study conducted between July 2004 and May 2006 among 21 754 surgical patients at a Swiss teaching hospital using a crossover design to compare 2 MRSA control strategies (rapid screening on admission plus standard infection control measures vs standard infection control alone). Twelve surgical wards including different surgical specialties were enrolled according to a prespecified agenda, assigned to either the control or intervention group for a 9-month period, then switched over to the other group for a further 9 months. INTERVENTIONS During the rapid screening intervention periods, patients admitted to the intervention wards for more than 24 hours were screened before or on admission by rapid, multiplex polymerase chain reaction. For both intervention (n=10 844) and control (n=10 910) periods, standard infection control measures were used for patients with MRSA in all wards and consisted of contact isolation of MRSA carriers, use of dedicated material (eg, gown, gloves, mask if indicated), adjustment of perioperative antibiotic prophylaxis of MRSA carriers, computerized MRSA alert system, and topical decolonization (nasal mupirocin ointment and chlorhexidine body washing) for 5 days. MAIN OUTCOME MEASURES Incidence of nosocomial MRSA infection, MRSA surgical site infection, and rates of nosocomial acquisition of MRSA. RESULTS Overall, 10 193 of 10 844 patients (94%) were screened during the intervention periods. Screening identified 515 MRSA-positive patients (5.1%), including 337 previously unknown MRSA carriers. Median time from screening to notification of test results was 22.5 hours (interquartile range, 12.2-28.2 hours). In the intervention periods, 93 patients (1.11 per 1000 patient-days) developed nosocomial MRSA infection compared with 76 in the control periods (0.91 per 1000 patient-days; adjusted incidence rate ratio, 1.20; 95% confidence interval, 0.85-1.69; P = .29). The rate of MRSA surgical site infection and nosocomial MRSA acquisition did not change significantly. Fifty-three of 93 infected patients (57%) in the intervention wards were MRSA-free on admission and developed MRSA infection during hospitalization. CONCLUSION A universal, rapid MRSA admission screening strategy did not reduce nosocomial MRSA infection in a surgical department with endemic MRSA prevalence but relatively low rates of MRSA infection. TRIAL REGISTRATION isrctn.org Identifier: ISRCTN06603006.

A Predictive Model for Identifying Surgical Patients at Risk of Methicillin-Resistant Staphylococcus aureus Carriage on Admission

BACKGROUND Legislative mandates and current guidelines for control of nosocomial transmission of methicillin-resistant Staphylococcus aureus (MRSA) recommend screening of patients at risk of MRSA carriage on hospital admission. Indiscriminate application of these guidelines can result in a large number of unnecessary screening tests. STUDY DESIGN This study was conducted to develop and validate a prediction model to define surgical patients at risk of previously unknown MRSA carriage on admission. We used data from two prospective studies to derivate and validate predictors of previously unknown MRSA carriage on admission, using logistic regression analysis. RESULTS A total of 13,262 patients (derivation cohort, 3,069; validation cohort, 10,193) were admitted to the surgery department and screened for MRSA. Prevalence of MRSA carriage at time of admission increased from 3.2% in 2003 to 5.1% in the period 2004 to 2006, with a majority of newly identified MRSA carriers (64%). Three independent factors were correlated with previously unknown MRSA carriage: recent antibiotic treatment (adjusted odds ratio [OR]: 4.5; p < 0.001), history of hospitalization (adjusted OR: 2.7; p = 0.03), and age older than 75 years (adjusted OR: 1.9; p = 0.048). A score (range 0 to 9 points) calculated from these variables was developed. Probability of previously unknown MRSA carriage was 5% (8 of 152) in patients with a low score (< 2 points), 11% (19 of 166) in those with an intermediate score (2 to 6 points), and 34% (30 of 87) in those with a high score (> or = 7 points). Limiting screening to patients with all 3 risk factors (21% and 26% of patients in the derivation and validation cohort, respectively) would have correctly identified 53% and 37% of MRSA carriers in both cohorts. CONCLUSIONS A predictive model using three easily retrievable determinants might help to better target surgical patients at risk of MRSA carriage on admission.

Comparison of strategies to reduce meticillin-resistant Staphylococcus aureus rates in surgical patients: a controlled multicentre intervention trial

Objective To compare the effect of two strategies (enhanced hand hygiene vs meticillin-resistant Staphylococcus aureus (MRSA) screening and decolonisation) alone and in combination on MRSA rates in surgical wards. Design Prospective, controlled, interventional cohort study, with 6-month baseline, 12-month intervention and 6-month washout phases. Setting 33 surgical wards of 10 hospitals in nine countries in Europe and Israel. Participants All patients admitted to the enrolled wards for more than 24 h. Interventions The two strategies compared were (1) enhanced hand hygiene promotion and (2) universal MRSA screening with contact precautions and decolonisation (intranasal mupirocin and chlorhexidine bathing) of MRSA carriers. Four hospitals were assigned to each intervention and two hospitals combined both strategies, using targeted MRSA screening. Outcome measures Monthly rates of MRSA clinical cultures per 100 susceptible patients (primary outcome) and MRSA infections per 100 admissions (secondary outcome). Planned subgroup analysis for clean surgery wards was performed. Results After adjusting for clustering and potential confounders, neither strategy when used alone was associated with significant changes in MRSA rates. Combining both strategies was associated with a reduction in the rate of MRSA clinical cultures of 12% per month (adjusted incidence rate ratios (aIRR) 0.88, 95% CI 0.79 to 0.98). In clean surgery wards, strategy 2 (MRSA screening, contact precautions and decolonisation) was associated with decreasing rates of MRSA clinical cultures (15% monthly decrease, aIRR 0.85, 95% CI 0.74 to 0.97) and MRSA infections (17% monthly decrease, aIRR 0.83, 95% CI 0.69 to 0.99). Conclusions In surgical wards with relatively low MRSA prevalence, a combination of enhanced standard and MRSA-specific infection control approaches was required to reduce MRSA rates. Implementation of single interventions was not effective, except in clean surgery wards where MRSA screening coupled with contact precautions and decolonisation was associated with significant reductions in MRSA clinical culture and infection rates. Trial registration clinicaltrials.gov identifier: NCT00685867

Risk factors for methicillin-resistant Staphylococcus aureus surgical site infection.

We prospectively evaluated 46 possible risk factors for methicillin-resistant Staphylococcus aureus (MRSA) surgical site infection (SSI) among patients with MRSA carriage in a large intervention study. Of 6,130 study patients, 68 (1.1%) developed MRSA SSI, which occurred a median of 14 days after surgery. Risk factors associated with MRSA SSI were receipt of emergency surgery, presence of comorbid condition, receipt of immunosuppressive therapy, receipt of contaminated surgery, and a surgical duration longer than the 75th percentile. MRSA carriage on admission did not predict MRSA SSI.

Burden of Bloodstream Infection Caused by Extended-Spectrum β-Lactamase–Producing Enterobacteriaceae Determined Using Multistate Modeling at a Swiss University Hospital and a Nationwide Predictive Model

OBJECTIVE To obtain an unbiased estimate of the excess hospital length of stay (LOS) and cost attributable to extended-spectrum β-lactamase (ESBL) positivity in bloodstream infections (BSIs) due to Enterobacteriaceae. DESIGN Retrospective cohort study. SETTING A 2,200-bed academic medical center in Geneva, Switzerland. PATIENTS Patients admitted during 2009. METHODS We used multistate modeling and Cox proportional hazards models to determine the excess LOS and adjusted end-of-LOS hazard ratio (HR) for ESBL-positive and ESBL-negative BSI. We estimated economic burden as the product of excess LOS and average bed-day cost. Patient-level accounting data provided a complementary analysis of economic burden. A predictive model was fitted to national surveillance data. RESULTS Thirty ESBL-positive and 96 ESBL-negative BSI cases were included. The excess LOS attributable to ESBL-positive and ESBL-negative BSI was 9.4 (95% confidence interval [CI], 0.4-18.4) and 2.6 (95% CI, 0.7-5.9) days, respectively. ESBL positivity was therefore associated with 6.8 excess days and CHF 9,473 per BSI. The adjusted end-of-LOS HRs for ESBL-positive and ESBL-negative BSI were 0.62 (95% CI, 0.43-0.89) and 0.90 (95% CI, 0.74-1.10), respectively. After reimbursement, the average financial loss per acute care episode in ESBL-positive BSI, ESBL-negative BSI, and control cohorts was CHF 48,674, 48,131, and 13,532, respectively. Our predictive model estimated that the nationwide cost of third-generation cephalosporin resistance would increase from CHF 2,084,000 in 2010 to CHF 3,526,000 in 2015. CONCLUSIONS This is the first hospital-wide analysis of excess LOS attributable to ESBL positivity determined using multistate modeling to avoid time-dependent bias. These results may inform health-economic evaluations of interventions targeting ESBL control.

Burden of meticillin-resistant Staphylococcus aureus infections at a Swiss University hospital: excess length of stay and costs

BACKGROUND Meticillin-resistant Staphylococcus aureus (MRSA) infections increase hospital costs primarily by prolonging patient length of stay (LOS). AIM To estimate the health-economic burden of MRSA infections at a Swiss University hospital using different analytical approaches. METHODS Excess LOS was estimated by: (i) multistate modelling comparing MRSA-infected and MRSA-free patients with MRSA infection as time-dependent exposure; (ii) matching MRSA-infected patients with a cohort of MRSA-uninfected patients. The economic impact was assessed by: (i) comparing cost estimates between MRSA-infected and MRSA-free patients and multiplying excess LOS by bed-day cost; (ii) comparing real costs between MRSA-infected and MRSA-colonized non-infected patients. FINDINGS The crude mean LOS was 37.3, 33.0 and 8.8 days for MRSA-infected, MRSA-colonized and MRSA-free patients, respectively. Excess LOS attributable to MRSA infection was 11.5 [95% confidence interval (CI): 7.9-15] or 15.3 days according to multistate modelling and matched analysis, respectively. The likelihood of discharge after MRSA infection was significantly reduced (adjusted hazard ratio: 0.69; 95% CI: 0.59-0.81). Average bed-day costs for MRSA-infected patients were 1.49- and 1.26-fold higher than for the general population hospitalized in acute wards and MRSA-colonized patients, respectively. MRSA infection resulted in an average additional cost of about 800 Swiss francs per day. CONCLUSIONS This analysis emphasizes the financial impact of MRSA infections, demonstrates the importance of accounting for time-dependent bias and confirms that multistate modelling is a valid strategy for estimating excess LOS and costs after MRSA infection.

Comparative Genomics of Community-Associated Methicillin-Resistant Staphylococcus aureus Shows the Emergence of Clone ST8-USA300 in Geneva, Switzerland

BACKGROUND Previous investigations of community-associated methicillin-resistant Staphylococcus aureus(CA-MRSA) isolates have revealed a wide diversity of genetic backgrounds, with only sporadic occurrence of ST8-USA300, in Geneva, Switzerland. We conducted a molecular epidemiologic analysis to identify the origin of a sudden increase of ST8 PVL-positive isolates in Geneva during 2013. METHODS On the basis of prospective CA-MRSA surveillance, we collected colonizing and infecting ST8-USA300 isolates and compared them to non-ST8 CA-MRSA isolates. Whole-genome sequencing (WGS) was performed for each isolate of this collection, and discriminating molecular features were linked to patient data. RESULTS In 2013, 22 isolates with the ST8-USA300 profile were identified among 46 cases of CA-MRSA. WGS revealed 2 groups of strains that differed by the type of the SCCmec IV element encoded and whether they harbored an arginine catabolism mobile element (ACME) locus. ACME-negative strains were mainly isolated from patients traveling in or originating from South America. Single-nucleotide polymorphism positions in isolate groups were used to infer their common ancestor, determine their geographical origin, and trace their relatedness. CONCLUSIONS WGS allowed the identification of transmission events and revealed that the increased prevalence of USA300 CA-MRSA isolates resulted from multiple importation events from the Americas but not from local clonal expansion of a successful clone.

P052: Molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) strains at Geneva University Hospitals (HUG) over a 9 year period

Changes within the MRSA population of single hospitals have been observed with certain clones replacing others. Surveillance of the genetic diversity within a hospital provides useful epidemiological data. Staphylococcal chromosomic cassettes (SCCmec) of MRSA isolates are routinely determined at HUG.

P053: Secular trends of methicillin-resistant Staphylococcus aureus (MRSA) at Geneva University Hospitals (HUG) over a 12-year period

Controlling MRSA has been a challenge for Geneva University Hospitals (HUG), particularly after the introduction of ST228 SCCmecI hyperendemic clone in 1999.

Epidemiology of MRSA at the University of Geneva Hospitals

Curbing MRSA has been a challenge for our institution, a hospital with hyperendemic MRSA since 1999.