Vancomycin-Resistant Enterococci (VRE) Arrives in Canada - A Case-Control Analysis of "The Call Bell" Outbreak.

L. LIOR*, M. LITT, J. HOCKIN, G. GILLIS, M. GARCIA, B.A. JOLLEY, C. KENNEDY, A. HUMAR, CONLY J.

The Laboratory Centre for Disease Control, Health Canada, Ottawa, ON, and The Toronto Hospital, University of Toronto, Toronto, ON, Canada.

Until 1995 no outbreaks of vancomycin-resistant enterococci (VRE) had ever been reported in Canada. The isolation of VRE from screening urine cultures of 2 patients on a renal ward in 08/95 prompted active surveillance for VRE from all patients on the ward, all dialysis patients, and all contacts. By 30/09/95, 26 patients were identified who were either colonized (26) or infected (1) with VRE. All but one case had been admitted to one module of the renal ward and we therefore conducted a case-control study to identify risk factors for colonization. Cases were defined as a Å perirectal/site swab for VRE >72 hours after admission between 01/07/95 and 30/09/95; controls were selected from the same time period and were admitted to the same module but had a Q perirectal/site swab. The case-control analysis included 19 cases and 34 controls. The mean age of the cases was 60.5 years (range 29-77); 57% were female. Univariate analysis revealed colonization was associated with diarrhea (OR=6.4); fecal incontinence (OR=___) while in hospital; recent antibiotic use (OR=9.8); multiple antibiotic use (OR=17.8); insertion of a urinary catheter (OR=4.8); peritoneal dialysis (OR=8.0); and >3 hospital admissions in the past year (OR=4.5). Longer hospital stays (>2 d) and longer stays on the module were also associated with colonization. Previous vancomycin use and proximity to the "index" room were not risk factors for colonization in this population. A separate survey of call bell usage found that >3 calls/24 hrs were associated with VRE colonization (p<0.001). Environmental cultures from call bells from one of the rooms were found to be Å for the same strain of VRE colonizing the patients. Persistence of call bell contamination was assessed after inoculation with 0.5 McFarlen broth and demonstrated viable VRE for up to 14 days. VRE persisted within crevices in the call bells despite phenolic disinfection of the exterior surface. Our analysis of the first Canadian outbreak of VRE has identified multiple risk factors identified previously and a unique risk factor, the "call bell" which may serve as a vector for ongoing transmission.

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