Microbiology of postthoractomy sternal wound infection

Specimens from 74 patients with postthoractomy sternal wound infection were studied for aerobic and anaerobic bacteria. Bacterial growth was obtained in specimens from 65 patients (88%). Aerobic or facultative bacteria only were recovered in 50 specimens (77%), anaerobic bacteria only in 6 (9%), and mixed aerobic, facultative, and anaerobic bacteria in 9 (14%). Eighty-seven isolates were recovered (1.3 per specimen): 68 aerobic or facultative (1.0 per specimen) and 19 anaerobic (0.3 per specimen). The predominant aerobes were Staphylococcus epidermidis (28 isolates), Staphylococcus aureus (21 isolates), and members of the family Enterobacteriaceae (14 isolates). The predominant anaerobes were Peptostreptococcus spp. (10 isolates), Bacteroides spp. (4 isolates), and Clostridium spp. (3 isolates). Polymicrobial infection occurred in 18 instances (28%). A single organisms was recovered in 47 instances (72%); these included 20 isolates of S. epidermidis, 15 of S. aureus, 5 of Enterobacteriaceae, and 4 of anaerobes. These data highlight the previously unrecognized polymicrobial aerobic and anaerobic bacteriology in a percentage of patients with postthoractomy sternal wound infection.