Outbreaks of Vancomycin-Resistant Enterococci in Hospital Settings: A Systematic Review and Calculation of the Basic Reproductive Number

BACKGROUND. Vancomycin-resistant enterococci (VRE) have spread worldwide. OBJECTIVE. To systematically review VRE outbreaks and estimate the pooled basic reproductive rate (R-0) of VRE. METHODS. Eligible studies criteria were (1) published within 10 years, (2) report outbreak details, (3) involve 1 center, (4) estimate epidemic duration, and (5) concern adults. Descriptive analysis included number of index cases, secondary cases, and screened patients; infection control measures; and definition of contact patients. R-0 was estimated by the equation R-0 = (ln2) D/t(d) + 1, with D as the generation time and t(d) as the doubling time. RESULTS. Thirteen VRE outbreaks were retained from 180 articles and, among them, 10 were kept for R-0 calculation. The mean (range) number of index cases was 2.3 (1-8) and the mean (range) number of secondary cases was 15 (3-56). The mean (range) number of screened patients was 174 (32-509), with pooled VRE prevalence of 5.4% (95% CI, 4.5%-6.3%). Contact precautions were reported in 12 studies (92%), wards were closed in 7 (54%), with cohorting in 6 (46%). Two major screening policies were implemented: (1) a surveillance program in the unit or hospital (7 studies [54%]) and (2) screening of selected contact patients (6 studies [46%]). The pooled R-0 of VRE was 1.32 (interquartile range, 1.03-1.46). CONCLUSION. We discerned considerable heterogeneity in screening policies during VRE outbreaks. Pooled R-0 was higher than 1, confirming the epidemic nature of VRE.