Epidemiological study of vancomycin-resistant enterococcus isolated from a single medical university hospital in Japan

Since 1998 more than 50 reports have described the isolation of high-level vancomycin-resistant enterococci (VRE) in Japan. Here, we report on our clinical isolates of VRE and an epidemiological study carried out using chemical and genetic techniques. VRE isolates were screened for high resistance to vancomycin (VCM) with a cutoff value of 6 μg/ml and VCM-resistant gene was confirmed by polymerase chain reaction (PCR). The epidemiological studies used pulsed-field gel electrophoresis (PFGE) and plasmid analysis. Six strains of VRE were isolated from six different patients on two wards during a 3-months period. All of the isolates possessed vanA on their plasmid, and the isolates were divided into two similar groups. Furthermore, three different patterns were defined by PFGE. Although all of the asymptomatic carriers were hospitalized for more than 3 months, we were able to prevent an outbreak of VRE in our hospital by using our guidelines for infection control, which are stricter than those for methicillin-resistant Staphylococcus aurens. From the results of this epidemiological study, we propose that there was a possibility of contamination in this hospital, and that three of the six isolates may have acquired vanA independently. In this study, we demonstrated that infection control, according to appropriate prevention guidelines, as well as regular surveillance for VRE, are essential for designing interventions to prevent the further spread of VRE.