Background: Coagulase-negative staphylococci cause 33% to 62.5% of wound infections after cardiac operations. The aim of this study was to investigate the sources of coagulase-negative staphylococci in the sternal wound.
Methods: Twenty operations performed in zonal ventilated operating rooms were investigated prospectively. Cultures were taken from all persons present in the room, the sternal wound, and the air. Isolates macroscopically judged to be coagulase-negative staphylococci were metabolically classified, and similar isolates were investigated by pulsed-field gel electrophoresis.
Results: Bacterial counts in the operating room air were very low. Wound contamination was found in 13 of 20 operations. Six wound isolates could be traced, three to the patients' sternal skin, one to the patient's groin, one to the surgeon's nose, and one to the surgeon's arm and forehead and the assistant's nose. Three operating field air cultures could be traced to the scrubbed theatre staff. The single case of superficial sternal wound infection was caused by Staphylococcus aureus, which was not isolated from the wound at operation.
Conclusions: In an ultraclean environment, bacteria in the sternal wound originated from the patients' own skin and from the surgical team.