Epidemiological, microbiological, clinical, and prognostic factors of bacteremia caused by high-level vancomycin-resistant Enterococcus species

A case-control study was performed between 1994 and 1996 in order to study the epidemiological, microbiological, clinical, and prognostic features of high-level vancomycin-resistant enterococcal bacteremia. Seventeen consecutive patients who had clinically significant bacteremia due to vancomycin-resistant enterococci (vanA genotype: 16 Enterococcus faecalis, 1 Enterococcus faecium) were compared with 169 who had vancomycin-susceptible enterococcal bacteremia. The following were selected by multivariate analysis as independent risk factors that influenced the development of high-level vancomycin-resistant enterococcal bacteremia: prior glycopeptide therapy (P=0.049); inclusion in a hemodialysis program (P=0.046); prior therapy with corticosteroids or antineoplastic agents (P=0.029); and prior surgical treatment (P=0.022). The following other factors were selected by univariate analysis: tracheostomy (P=0.002); prolonged hospitalization (P=0.01); and any kind of puncture (P=0.02). The crude associated-mortality rate was 13.4%. Gene amplification of vanA was positive for 17 strains of enterococci. Pulsed-field gel electrophoresis of genomic DNA after SmaI digestion of vanA isolates revealed that one strain predominated (10 isolates), though at least four similar banding patterns were identified (6 isolates). The 16 strains closely related to the outbreak were investigated further. The surgical intensive care unit was the first and most involved service. The hospital outbreak of vanA vancomycin-resistant enterococcal bacteremia occurred between 1994 and 1995 and was caused by Enterococcus faecalis. This is believed to be the first and only such outbreak described in a Spanish hospital thus far.