Improving prediction of surgical site infection risk with multilevel modeling.

BACKGROUND: Surgical site infection (SSI) surveillance is a key factor in the elaboration of strategies to reduce SSI occurrence and in providing surgeons with appropriate data feedback (risk indicators, clinical prediction rule). AIM: To improve the predictive performance of an individual-based SSI risk model by considering a multilevel hierarchical structure. PATIENTS AND METHODS: Data were collected anonymously by the French SSI active surveillance system in 2011. An SSI diagnosis was made by the surgical teams and infection control practitioners following standardized criteria. A random 20% sample comprising 151 hospitals, 502 wards and 62280 patients was used. Three-level (patient, ward, hospital) hierarchical logistic regression models were initially performed. Parameters were estimated using the simulation-based Markov Chain Monte Carlo procedure. RESULTS: A total of 623 SSI were diagnosed (1%). The hospital level was discarded from the analysis as it did not contribute to variability of SSI occurrence (p  = 0.32). Established individual risk factors (patient history, surgical procedure and hospitalization characteristics) were identified. A significant heterogeneity in SSI occurrence between wards was found (median odds ratio [MOR] 3.59, 95% credibility interval [CI] 3.03 to 4.33) after adjusting for patient-level variables. The effects of the follow-up duration varied between wards (p<10-9), with an increased heterogeneity when follow-up was <15 days (MOR 6.92, 95% CI 5.31 to 9.07]). The final two-level model significantly improved the discriminative accuracy compared to the single level reference model (p<10-9), with an area under the ROC curve of 0.84. CONCLUSION: This study sheds new light on the respective contribution of patient-, ward- and hospital-levels to SSI occurrence and demonstrates the significant impact of the ward level over and above risk factors present at patient level (i.e., independently from patient case-mix).

Changing trends in vancomycin-resistant enterococci in French hospitals, 2001-08.

OBJECTIVES: Unprecedented outbreaks of vancomycin-resistant enterococci (VRE) have occurred in French hospitals since 2004. The aim of this study was to provide a picture of the spread and control of VRE in France and to characterize the isolates. METHODS: Notification of VRE cases to Institut de Veille Sanitaire has been mandatory since 2001. Isolates of VRE were sent to the National Reference Centre for species and vancomycin-resistance gene identification. Isolates were tested for antimicrobial susceptibility and typed by PFGE and multilocus sequence typing. RESULTS: Five hundred and four VRE notifications from 195 hospitals were recorded, corresponding to 2475 cases of infection (n=243) or colonization (n=2232) and 74 episodes of clustered cases. Outbreaks were controlled by implementation of infection control measures, although the number of new hospitals reporting isolation of VRE was increasing. The majority of 902 VRE isolated from 2006 to 2008 were Enterococcus faecium (94.8%) with the vanA or vanB gene. No isolate was resistant to linezolid, tigecycline or fusidic acid. PFGE analysis showed 161 different patterns. Generally a few predominant clones and several minor clones spread in a single hospital. In a subset of 46 representatives of PFGE clones, 13 different sequence types were characterized, all belonging to clonal complex CC17, while the esp and hyl genes were inconsistently detected. CONCLUSIONS: The national mandatory notification of unusual nosocomial events allowed rapid identification of VRE outbreaks and early implementation of control measures that have proved effective. However, VRE continue to emerge in a growing number of hospitals.

Control of a regional outbreak of vanA glycopeptide-resistant Enterococcus faecium, Eastern France, 2004-2009.

At the end of 2004, an outbreak of glycopeptide-resistant enterococci (GRE) spread from the Nancy Teaching Hospital to more than 40 facilities in the Lorraine region. Because this outbreak appeared to be uninhibited, a regional task force was set up to organize and co-ordinate the management of the outbreak, visiting the affected facilities to publicize the existing recommendations and take stock of the problems encountered in the field. The task force then proposed control measures specific to the region. The proposed measures included promoting the use of alcohol-based hand-rub solutions, isolation measures, enhanced screening policies, cohorting GRE-colonized patients and contacts in special wards with dedicated staff where possible, or failing that, isolating them in single rooms with additional "contact" precautions, maintaining these precautions for GRE-colonized patients until a negative stool sample was obtained after antibiotic treatment (which is a more restrictive definition of "cleared" than usually employed), regional co-ordination of the follow-up of GRE-colonized patients with the weekly publication of a list of institutions that were or had been affected to allow isolation measures to be adopted as soon as known-GRE-colonized patient were readmitted. It was not possible to determine the efficacy of each individual measure on the course of the outbreak. Nevertheless, we observed that the number of new GRE-colonized patients started to decrease following their implementation. Ultimately, 1077 GRE colonizations were recorded in Lorraine, and the outbreak is now under control.

Relationship between the prevalence of methicillin-resistant Staphylococcus aureus infection and indicators of nosocomial infection control measures: a population-based study in French hospitals.

OBJECTIVE: To assess whether infection control indicators are associated with the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infection in French hospitals. METHODS: We linked the database for the 2006 national prevalence survey of nosocomial infection with the database of infection control indicators (comprised of ICALIN, an indicator of infection control organization, resources, and action, and ICSHA, an indicator of alcohol-based handrub consumption) recorded from hospitals by the Ministry of Health. Data on MRSA infection were obtained from the national prevalence survey database and included the site and origin of infection, the microorganism responsible, and its drug resistance profile. Because the prevalence of MRSA infection was low and often nil, especially in small hospitals, we restricted our analysis to hospitals with at least 300 patients. We used a multilevel logistic regression model to assess the joint effects of patient-level variables (eg, age, sex, or infection) and hospital-level variables (infection control indicators). RESULTS: Two hundred two hospitals had at least 300 patients, for a total of 128,631 patients. The overall prevalence of MRSA infection was 0.34% (95% confidence interval [CI], 0.29%-0.39%). The mean value for ICSHA was 7.8 L per 1,000 patient-days (median, 6.1 L per 1,000 patient-days; range, 0-33 L per 1,000 patient-days). The mean value for ICALIN was 92 of a possible 100 points (median, 94.5; range, 67-100). Multilevel analyses showed that ICALIN scores were associated with the prevalence of MRSA infection (odds ratio for a score change of 1 standard deviation, 0.80; 95% CI, 0.69-0.93). We found no association between prevalence of MRSA infection and ICSHA. Other variables significantly associated with the prevalence of MRSA infection were sex, vascular or urinary catheter, previous surgery, and the McCabe score. CONCLUSIONS: We found a significant association between the prevalence of MRSA infection and ICALIN that suggested that a higher ICALIN score may be predictive of a lower prevalence of MRSA infection.

A cluster of Vibrio cholerae O1 infections in French travelers to Rajasthan (India), May 2006.

A woman aged 60 years was hospitalized for Vibrio cholerae serogroup O1 cholera. Twenty-six fellow travelers and 48 health care workers who cared for the patient were individually traced and contacted. Of the 23/27 travelers with diarrhea during the trip, 4 presented antibodies. There was no person-to-person transmission.