Variable performance of models for predicting methicillin-resistant Staphylococcus aureus carriage in European surgical wards.

BACKGROUND: Predictive models to identify unknown methicillin-resistant Staphylococcus aureus (MRSA) carriage on admission may optimise targeted MRSA screening and efficient use of resources. However, common approaches to model selection can result in overconfident estimates and poor predictive performance. We aimed to compare the performance of various models to predict previously unknown MRSA carriage on admission to surgical wards. METHODS: The study analysed data collected during a prospective cohort study which enrolled consecutive adult patients admitted to 13 surgical wards in 4 European hospitals. The participating hospitals were located in Athens (Greece), Barcelona (Spain), Cremona (Italy) and Paris (France). Universal admission MRSA screening was performed in the surgical wards. Data regarding demographic characteristics and potential risk factors for MRSA carriage were prospectively collected during the study period. Four logistic regression models were used to predict probabilities of unknown MRSA carriage using risk factor data: "Stepwise" (variables selected by backward elimination); "Best BMA" (model with highest posterior probability using Bayesian model averaging which accounts for uncertainty in model choice); "BMA" (average of all models selected with BMA); and "Simple" (model including variables selected >50% of the time by both Stepwise and BMA approaches applied to repeated random sub-samples of 50% of the data). To assess model performance, cross-validation against data not used for model fitting was conducted and net reclassification improvement (NRI) was calculated. RESULTS: Of 2,901 patients enrolled, 111 (3.8%) were newly identified MRSA carriers. Recent hospitalisation and presence of a wound/ulcer were significantly associated with MRSA carriage in all models. While all models demonstrated limited predictive ability (mean c-statistics <0.7) the Simple model consistently detected more MRSA-positive individuals despite screening fewer patients than the Stepwise model. Moreover, the Simple model improved reclassification of patients into appropriate risk strata compared with the Stepwise model (NRI 6.6%, P = .07). CONCLUSIONS: Though commonly used, models developed using stepwise variable selection can have relatively poor predictive value. When developing MRSA risk indices, simpler models, which account for uncertainty in model selection, may better stratify patients' risk of unknown MRSA carriage.

Interventions to reduce colonisation and transmission of antimicrobial-resistant bacteria in intensive care units: an interrupted time series study and cluster randomised trial.

BACKGROUND: Intensive care units (ICUs) are high-risk areas for transmission of antimicrobial-resistant bacteria, but no controlled study has tested the effect of rapid screening and isolation of carriers on transmission in settings with best-standard precautions. We assessed interventions to reduce colonisation and transmission of antimicrobial-resistant bacteria in European ICUs. METHODS: We did this study in three phases at 13 ICUs. After a 6 month baseline period (phase 1), we did an interrupted time series study of universal chlorhexidine body-washing combined with hand hygiene improvement for 6 months (phase 2), followed by a 12-15 month cluster randomised trial (phase 3). ICUs were randomly assigned by computer generated randomisation schedule to either conventional screening (chromogenic screening for meticillin-resistant Staphylococcus aureus [MRSA] and vancomycin-resistant enterococci [VRE]) or rapid screening (PCR testing for MRSA and VRE and chromogenic screening for highly resistant Enterobacteriaceae [HRE]); with contact precautions for identified carriers. The primary outcome was acquisition of resistant bacteria per 100 patient-days at risk, for which we calculated step changes and changes in trends after the introduction of each intervention. We assessed acquisition by microbiological surveillance and analysed it with a multilevel Poisson segmented regression model. We compared screening groups with a likelihood ratio test that combined step changes and changes to trend. This study is registered with ClinicalTrials.gov, number NCT00976638. FINDINGS: Seven ICUs were assigned to rapid screening and six to conventional screening. Mean hand hygiene compliance improved from 52% in phase 1 to 69% in phase 2, and 77% in phase 3. Median proportions of patients receiving chlorhexidine body-washing increased from 0% to 100% at the start of phase 2. For trends in acquisition of antimicrobial-resistant bacteria, weekly incidence rate ratio (IRR) was 0·976 (0·954-0·999) for phase 2 and 1·015 (0·998-1·032) for phase 3. For step changes, weekly IRR was 0·955 (0·676-1·348) for phase 2 and 0·634 (0·349-1·153) for phase 3. The decrease in trend in phase 2 was largely caused by changes in acquisition of MRSA (weekly IRR 0·925, 95% CI 0·890-0·962). Acquisition was lower in the conventional screening group than in the rapid screening group, but did not differ significantly (p=0·06). INTERPRETATION: Improved hand hygiene plus unit-wide chlorhexidine body-washing reduced acquisition of antimicrobial-resistant bacteria, particularly MRSA. In the context of a sustained high level of compliance to hand hygiene and chlorhexidine bathings, screening and isolation of carriers do not reduce acquisition rates of multidrug-resistant bacteria, whether or not screening is done with rapid testing or conventional testing. FUNDING: European Commission.

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.

Ten-year decrease of acquired methicillin-resistant Staphylococcus aureus (MRSA) bacteremia at a single institution: the result of a multifaceted program combining cross-transmission prevention and antimicrobial stewardship.

BACKGROUND: In France, the proportion of MRSA has been over 25% since 2000. Prevention of hospital-acquired (HA) MRSA spread is based on isolation precautions and antibiotic stewardship. At our institution, before 2000, the Infection Disease and the Infection Control teams had failed to reduce HA-MRSA rates. OBJECTIVES AND METHODS: We implemented a multifaceted hospital-wide prevention program and measured the effects on HA-MRSA colonization and bacteremia rates between 2000 and 2009. From 2000 to 2003, active screening and decontamination of ICU patients, hospital wide alcohol based hand rubs (ABHR) use, control of specific classes of antibiotics, compliance audits, and feed-backs to the care providers were successively implemented. The efficacy of the program was assessed by HA-MRSA colonized and bacteremic patient rates per 1000 patient-days in patients hospitalized for more than twenty-four hours. RESULTS: Compliance with the isolation practices increased between 2000 and 2009. Consumption of ABHR increased from 6.8 L to 27.5 L per 1000 patient-days. The use of antibiotic Defined Daily Doses (DDD) per 1000 patient-days decreased by 31%. HA-MRSA colonization decreased by 84% from 1.09 to 0.17 per 1000 patient-days and HA-MRSA bacteremia by 93%, from 0.15 to 0.01 per 1000 patient-days (p < 10-7 for each rate). CONCLUSIONS: In an area highly endemic for MRSA, a multifaceted prevention program allows for sustainable reduction in HA-MRSA bacteremia rates.

Hand hygiene practices and adherence determinants in surgical wards across Europe and Israel: a multicenter observational study.

We examined hand hygiene practices in surgical wards in 9 countries in Europe and Israel through direct practice observation. There was marked interhospital variation in hand hygiene compliance (range, 14%-76%), as well as glove and alcohol-based handrub use. After multivariable analysis, surgical subspecialty, professional category, type of care activity, and workload were independently associated with compliance. Hand hygiene practices are influenced by numerous factors, and a tailored approach may be required to improve practices.

Supplemental treatment of air in airborne infection isolation rooms using high-throughput in-room air decontamination units.

BACKGROUND: Evidence has recently emerged indicating that in addition to large airborne droplets, fine aerosol particles can be an important mode of influenza transmission that may have been hitherto underestimated. Furthermore, recent performance studies evaluating airborne infection isolation (AII) rooms designed to house infectious patients have revealed major discrepancies between what is prescribed and what is actually measured. METHODS: We conducted an experimental study to investigate the use of high-throughput in-room air decontamination units for supplemental protection against airborne contamination in areas that host infectious patients. The study included both intrinsic performance tests of the air-decontamination unit against biological aerosols of particular epidemiologic interest and field tests in a hospital AII room under different ventilation scenarios. RESULTS: The unit tested efficiently eradicated airborne H5N2 influenza and Mycobacterium bovis (a 4- to 5-log single-pass reduction) and, when implemented with a room extractor, reduced the peak contamination levels by a factor of 5, with decontamination rates at least 33% faster than those achieved with the extractor alone. CONCLUSION: High-throughput in-room air treatment units can provide supplemental control of airborne pathogen levels in patient isolation rooms.

Highly sensitive and efficient computer-assisted system for routine surveillance for surgical site infection.

OBJECTIVES: Surveillance of surgical site infections (SSIs) is effective in reducing the rates of these complications, but it is extremely time-consuming and, consequently, underused. We determined the sensitivity and specificity of a computer-assisted surveillance system, compared with a conventional method involving review of medical records, and the time saved with the computer-assisted system. METHOD: A prospective study was conducted from January 1 to December 31, 2001. With the computer-assisted method, screening for SSIs relied on identification in the laboratory database of positive results of microbiological tests of surgical-site specimens; confirmation was obtained via computer-generated questionnaires completed by the surgeon in charge of the patient. In the conventional method, SSIs were identified by exhaustive chart review. The time spent on surveillance was recorded for both methods. SETTING: A 25-bed gastrointestinal surgery unit in a tertiary care hospital. PATIENTS: A total of 766 consecutive patients who underwent gastrointestinal surgery. RESULTS: The sensitivity of the computer-assisted method was 84.3% (95% confidence interval, 0.66-0.94); the specificity was 99.9%. For the 807 surgical procedures in the study, 197 had an SSI identified by culture of a surgical-site specimen. After elimination of 63 duplicate cultures with positive results, 134 questionnaires were sent to the surgeons, who confirmed 27 SSIs. The conventional method identified 32 SSIs. The computer-assisted method required 60% less time than the conventional method (90 hours vs 223 hours). CONCLUSION: Surveillance for SSIs using computer-assisted, laboratory-based screening and case confirmation by surgeons is as efficient as and far less time-consuming than the conventional method of chart review. This method permits routine surveillance for SSIs with reliable accuracy.

Epidemiology and control of antibiotic resistance in the intensive care unit.

PURPOSE OF REVIEW: Resistance to antibiotics is very high in the intensive care units of many countries, although there are several exceptions. Some infections are becoming extremely difficult to treat. The risk of cross-transmission of those strains is very high. This review focuses on recent data (2003 to the present) that may help understanding and dealing with this serious public health problem. RECENT FINDINGS: Intensive care units can be considered as 'factories' for creating, disseminating and amplifying resistance to antibiotics, for many reasons: importation of resistant microorganisms at admission, selection of resistant strains with an extensive use of broad-spectrum antibiotics, cross-transmission of resistant strains via the hands or the environment. Some national programs can be considered as failures, as in the UK and the USA. Other countries have been able to maintain a low level of resistance (Scandinavian countries, Netherlands, Switzerland, Germany, Canada). There is clearly an 'inoculum effect' above which preventive measures become poorly efficient. Several preventive measures have been proposed including preventive isolation, systematic screening at admission, local, national or international antibiotic guidelines, antibiotic prescriptions advice by infectious-disease teams, antibiotic prevention with selective digestive decontamination, antibiotic strategies such as 'cycling', or rather, for some authors, the use of an 'à la carte' antibiotic strategy which could be considered as a 'patient-to-patient antibiotic rotation'. SUMMARY: There is obviously an international concern regarding the level of resistance to antibiotics in the intensive-care-unit setting. A strong program including prevention of cross-transmission and better usage of antibiotics seems to be needed in order to be successful. We do not know if this kind of program will enable countries with a very high endemic level of resistance to decrease the level in future years.

Clinical and therapeutic features of nonpostoperative nosocomial intra-abdominal infections.

OBJECTIVE: To compare the clinical, microbiological, and therapeutic features of nonpostoperative nosocomial intra-abdominal infections (non-PostopNAI) with community-acquired intra-abdominal infections (CAI). SUMMARY BACKGROUND DATA: Prospective (June 2000 through January 2001) consecutive case series analysis of patients operated for secondary nonpostoperative intra-abdominal infections collected in 176 study centers (surgical wards and intensive care units). PATIENTS AND METHODS: Clinical, microbiological, and therapeutic characteristics of CAI and non-PostopNAI infections were collected. Management of antibiotic therapy was decided by the attending physician. The efficacy of treatment was evaluated over a 30-day period after the index episode. RESULTS: Evaluatable observations (n = 1008) were collected (761 CAI and 247 non-PostopNAI), including 285 intensive care unit patients. When compared with CAI patients, non-PostopNAI patients presented an increased interval between admission to the surgical ward and operation (1.3 +/- 1.5 vs. 0.5 +/- 0.7 days in CAI patients; P < 0.001), increased proportions of underlying diseases, a more severe clinical condition as assessed by increased proportions of hospitalization in the intensive care unit (48% vs. 22% in CAI patients, P < 0.001) and a higher SAPS II score (34 +/- 15 vs. 24 +/- 14, P < 0.001). In non-PostopNAI patients, increased proportions of therapeutic failure (15% vs. 7% in CAI patients, P < 0.01) and of fatalities (12% vs. 4% in CAI patients, P < 0.001) were observed. CONCLUSIONS: Delayed diagnosis and increased severity are the main characteristics of non-PostopNAI infections. Microbiological features are quite similar in CAI and non-PostopNAI infections, suggesting that antibiotic therapy recommended for CAI infections could be applied to non-PostopNAI patients. Characteristics of non-PostopNAI patients should lead to identify them as a specific entity in clinical trials.

A continuous quality-improvement program reduces nosocomial infection rates in the ICU.

OBJECTIVE: To assess the impact of a continuous quality-improvement program on nosocomial infection rates. DESIGN AND SETTING: Prospective single-center study in the medical-surgical ICU of a tertiary care center. PATIENTS. We admitted 1764 patients during the 5-year study period (1995-2000); 55% were mechanically ventilated and 21% died. Mean SAPS II was 37+/-21 points and mean length of ICU stay was 9.7+/-16.1 days. INTERVENTIONS: Implementation of an infection control program based on international recommendations. The program was updated regularly according to infection and colonization rates and reports in the literature. MEASUREMENTS AND RESULTS: Prospective surveillance showed the following rates per 1000 procedure days: ventilator-associated pneumonia (VAP) 8.7, urinary tract infection (UTI) 17.2, central venous catheter (CVC) colonization 6.1, and CVC-related bacteremia and 2.0; arterial catheter colonization did not occur. In the 5 years following implementation of the infection control program there was a significant decline in the rate per patient days of UTI, CVC colonization, and CVC-related bacteremia but not VAP. Between the first and second 2.5-year periods the time to infection increased significantly for UTI and CVC-related colonization. CONCLUSIONS: A continuous quality-improvement program based on surveillance of nosocomial infections in a nonselected medical-surgical ICU population was associated with sustained decreases in UTI and CVC-related infections.