The occurrence of Staphylococcus epidermidis in a department of thoracic and cardiovascular surgery. A clinical and epidemiological investigation.

Changes in resistance traits of Staphylococcus epidermidis isolated in the preoperative and postoperative phases from patients undergoing open heart surgery were studied in a two-step prospective investigation. Period 1 comprised 32 patients. All received streptomycin for five days and methicillin for seven days, starting the evening before operation. None of the patients was colonized with multiresistant (MR) strains before or immediately after operation. Two days after operation, in the intensive care unit (ICU) 79% of the patients carried MR S. epidermidis in the nose. Air analyses showed that 30% of the bacteria isolated from the ICU were MR, while such strains were seldom found in the operating theatre. Nose swabs from the staff showed that 26% at the ICU and none in the operating theatre carried MR strains. In an attempt to counteract the selection for MR strains, all patients in period 2 received methicillin alone for only 3 days, and disinfection of the ICU was then performed after each patient. Period 2 comprised 105 patients. The frequency of MR S. epidermidis in the patient material declined from 80% to 40% and from 26% to 15% in the staff members. No changes were found concerning the frequency of postoperative complications. The conclusion is that methicillin alone for three days gives as good a protection against postoperative infections as a more broad-spectrum treatment and that reduced use of antibiotics will reduce the risk of early colonization with resistant strains.