Epidemiology of Vancomycin-Resistant Enterococci in Various Medical Wards

Abstract

Background. Vancomycin-resistant enterococci (VRE) have become one of the leading cause of health care-associated infections. Data on occurrence and spread of these pathogens in different types of hospital units are needed to develop effective surveillance and control measures to prevent dissemination of VRE. Aim. The aim of this study was to define hospital units with high risk of VRE dissemination in health care facilities of St. Petersburg. Materials and Methods. Point-prevalence study of colonisation and infection in patients and contamination of the environment was conducted during 2013 - 2014 in 8 hospital units of different types: neonatal intensive care, newborn pathology, general paediatric surgery, bone marrow transplantation (BMT for adolescents), cancer surgery of the gastrointestinal (GI) tract and breast cancer, haemodialysis (three units). In each unit microbiological testing of clinical (N=857) and environmental (N=508) samples was conducted three times a months during the study period. Verification of vancomycin resistance in enterococci was conducted by amplification of vanA and vanB cassettes according to the technique developed by S. Dutka-Malen et al. Molecular genetic typing of enterococci by random amplification of polymorphic DNA (RAPD-PCR) was performed with universal primer R5 (5’-AACGCGCAAC-3’) in the concentration of 50 pmol/^L, according to the protocol proposed by B. Martin et al. VNTR analysis was performed according to the technique published by J. Top et al. Results. Colonization of patients and contamination of environment by VRE were detected only in haemato-oncologyunits (21,6 per 100 patients, 2,6 per 100 environmental swabs), neonatal intensive care (16,7 per 100 patients, 8,5 per 100 environmental swabs), and newborn pathology (34,6 per 100 patients, 3,3 per 100 environmental swabs). VRE were detected on the related to patient care environmental objects in common use for all patients (scales, changing tables, procedure tables, sink faucets) in the neonatal intensive care units and non-medical objects shared by all patients (tables in patient rooms, microwave oven and refrigerators shelves) in the haemato-oncology unit. The molecular genetic typing showed that strains of VRE isolated from patients and the environment were identical. Vancomycin resistance due to presence of vanA was dominating. Conclusion. Neonatal and haemato-oncology departments were identified as high risk hospital units. The most common mode of transmission of VRE is contact transmission via hands of health care workers in neonatal units and via environmental objects in haemato-oncology. To contain dissemination of VRE in the high risk units, development of microbiological monitoring of VRE and measures to control their transmission is needed.