Nosocomial Staphylococcus epidermidis septicaemia among very low birth weight neonates in an intensive care unit.

A cluster of cases of septicaemia caused by coagulase-negative staphylococci was observed among the infants at the Neonatal Intensive Care Unit (NICU) of the Karolinska Hospital in May 1987. The presence of a unique antibiogram among the blood culture isolates prompted an investigation to determine whether an epidemic strain existed or not, using antibiogram, biotyping and plasmid profiles as epidemiological markers. All 14 isolates with a unique antibiogram were investigated, and 22 isolates without the unique antibiogram served as controls. Of the 14 isolates, 11 were Staphylococcus epidermidis and had similar plasmid patterns. Of the 22 control isolates, 15 were S. epidermidis, and none had the special plasmid pattern nor any other recurring plasmid patterns. The use of plasmid profile analysis together with antibiograms thus identified a possible epidemic strain of S. epidermidis which may have been responsible for the upsurge of septicaemia cases at the NICU. The presence of an epidemic strain implies that hospital cross infection control could be important in preventing neonatal septicaemia caused by S. epidermidis.