Endemic Nosocomial Transmission of Staphylococcus epidermidis Bacteremia Isolates in a Neonatal Intensive Care Unit over 1O Years

To assess long-term nosocomial transmission, trends in antibiotic resistance, and expression of potential virulence factors, 86 randomly selected Staphylococcus epidermidis bloodstream isolates obtained from 80 patients in a neonatal intensive care unit (NICU) over a 10-year period were studied. Pulsed-field gel electrophoresis (PFGE) analysis of SmaI-digested whole chromosomal DNA revealed distinctive banding patterns that persisted in the NICU over long periods. Pattern A included 22 isolates (26%) obtained during 1983-1990, and pattern B included 24 isolates (28%) from 1983 to 1991. All 10 isolates examined in 1984 fell into one of these two patterns. Isolates with either pattern expressed polysaccharide/adhesin (PSA) and slime; 90% and 87% were resistant to oxacillin and gentamicin, respectively, with no trends over time. These findings suggest that distinct clones of S. epidermidis can become endemic in NICUs over periods as long as a decade and that nosocomial transmission plays an important role in neonatal S. epidermidis bacteremia.