Contamination of blood during cardiopulmonary bypass: the effect of antibiotic prophylaxis

Despite antibiotic prophylaxis in cardiac surgery, gram-positive bacteria can be isolated in up to 10% of intraoperative blood cultures. During a prospective randomized trial, blood was collected from the oxygenator at the end of bypass in 58 patients given teicoplanin and in 60 others given flucloxacillin and tobramycin. Coagulase-negative staphylococci were cultured from 16 patients given teicoplanin but in only four cases after flucloxacillin and tobramycin (Fisher's exact test, P = 0.005). In contrast, Propionibacterium spp. or coryneforms were isolated from 22 patients given flucloxacillin and tobramycin and from only one patient in the teicoplanin group. There were no cases of prosthetic valve endocarditis. After 3 h exposure to 4 x MIC of teicoplanin there was only a 10-60 fold reduction in cfus of Staphylococcus epidermidis, which may partly explain the excess of these organisms.