Investigation into the repeated recovery of coagulase-negative staphylococci from blood taken at the end of cardiopulmonary by-pass.

Forty-six strains of coagulase-negative staphylococci (CNS) were typed by biochemical reactivity, antibiotic susceptibility pattern, macrorestriction analysis by pulsed-field gel electrophoresis (PFGE) and arbitrary primed polymerase chain reaction (AP PCR). Twenty-four strains were obtained in 1993 from blood cultures of as many patients coupled to a heart-lung machine during cardiac surgery. Since over 30% of the latter belonged to a single type, it was concluded that during the year of analysis a single clone of CNS persisted in this hospital setting. Subsequent epidemiological surveillance putatively identified four possible carriers among surgical personnel. For this reason, 22 strains collected from the hands and nose of two cardiac surgeons and two perfusionists were also tested; none were identical to the persistent clone. Thus either the operation equipment was colonized longitudinally or the causative CNS had disappeared from the suspect individuals' flora. Longitudinal monitoring of CNS infections by various techniques gives a valuable insight into nosocomial epidemiology and elucidates the complexity of the CNS colonization.