Antibiotic-resistant Staphylococcus epidermidis in patients undergoing cardiac surgery

Staphylococcus epidermidis isolates containing subpopulations resistant to 100 microgram of methicillin per ml were found on the chests of only 3 of 80 (4%) patients before cardiac surgery, whereas these highly resistant staphylococci were isolated from the chest wounds of 43 of 80 (54%) patients 5 days postoperatively. The percentage of patients colonized with methicillin-resistant S. epidermidis increased with time postoperatively. Methicillin-resistant postoperative isolates also contained organisms resistant to other antibiotics frequently used during these patients' hospitalizations. The percentages of patients with organisms resistant to various antibiotics were: nafcillin (100%), penicillin (100%), cephalothin (93%), cefamandole (80%), streptomycin (67%), and gentamicin (20%). Preoperative methicillin-susceptible isolates were generally susceptible to other antibiotics. Two patients with S. epidermidis prosthetic valve endocariditis caused by multiple antibiotic-resistant isolates were among the study patients. Antibiotic susceptibility patterns of each isolate from these two patients were identical to those of postoperative chest isolates from the same patient.