PCR melting profile method for genotyping analysis of vancomycin-resistant Enterococcus faecium isolates from hematological unit patients

A number of Enterococcus strains with high-level inducible resistance to vancomycin have been identified, and the relative incidence of these strains has increased significantly in the last years. The first outbreak caused by vancomycin-resistant enterococci in Poland was reported in 1999. Vancomycin-resistant Enterococcus faecium is known for its propensity to cause infections which are difficult to eradicate. In this study, we determined the genetic similarities between vancomycin-resistant E. faecium isolates consecutively recovered from single patients to assess the duration of infection or colonization. The isolates taken in the study were identified by the conventional methods as E. faecium. PCRmelting profile (PCR-MP) and pulsed-field gel electrophoresis (PFGE) typing revealed that the isolates belonged to six distinct genotypes and that two of them were predominant. Consecutive E. faecium isolates with identical genotypes were found in 7 of 12 (58.0%) patients. The delay between the times of recovery of the first and last isolates of identical genotypes from each patient was from 9 days to about 1 year. In six patients, paired blood and non-blood isolates showed identical genotypes. Data presented here demonstrate the complexity of the epidemiological situation concerning vancomycin-resistant enterococci that may occur in a single medical ward. We also show for the first time the evaluation of PCR-MP technique in enterococci strains differentiation and we revealed that there is at least a similar power of discrimination between the presentjjold-standard REA-PFGE and a PCR-MP method.