Molecular epidemiological analysis of vancomycin-resistant enterococci

Abstract

Introduction: In the control of vancomycin-resistant enterococci (VRE), it is important to identify these bacteria rapidly and demonstrate their relationship with nosocomial outbreaks. In this study we aimed to investigate epidemiology of VRE strains by determination of clonal relationships of these bacteria.Material and Method: The VRE strains isolated from January 2001 to December 2009 were examined in terms of their distribution by year and by their clustering patterns into epidemic groups. Identification and antibiotic susceptibilities were tested by using the otomated system. Vancomycin resistance was confirmed by the E-test method. PFGE was used to determine the clonal relationship between the strains.Results: 664 VRE strains were isolated in periods of nine years. E. faecium was found to be the most prevalent species. Eigthy-three E. faecium strains isolated during the epidemic periods were characterized by PFGE types from 11 different clonal clusters. The largest of these clusters, F-2, contained 26 isolates which was isolated in 2009. There was a significant similarity between strains isolated in 2001 and 2002 epidemics. The F-4 clone containing five isolates was first identified in 2001, and then detected in 2003. The strains isolated in the other three epidemic periods displayed certain insignificant similarities.Discussion: E. faecium which has been increasing among the VRE species all over the world, was found to be the most common isolate. In this study, a significant similarity was observed between strains isolated in the epidemics of 2001 and 2002, which indicates that this clone survived for a long time and became prevalent in the hospital during this period. All the strains in the 2009 epidemic period were clustered in one clone, F-2. Since this clone had not previously been isolated in our hospital, it is considered that it spreaded in the hospital and was the only clone responsible for the epidemic of 2009. To prevent VRE spread that may result hospital epidemics, it is important to well informe and educate our staff concerning these infections and preventive measures.