A 12 year study of aerobic and anaerobic bacteria in intra-abdominal and postsurgical abdominal wound infections.

Findings from the study of aerobic and anaerobic bacteria in intra-abdominal infections from 339 specimens of the peritoneal cavity after intestinal perforation, 83 specimens from abdominal abscesses and 89 specimens from postsurgical abdominal wounds are presented. Anaerobic bacteria alone were present in 43 (13 per cent) of the peritoneal specimens, aerobic bacteria alone in 38 (11 per cent) and mixed aerobic and anaerobic flora in 258 (76 per cent). A total of 985 bacterial isolates were recovered in peritoneal specimens (2.9 per specimen), with 436 aerobes (1.3 per specimen) and 549 anaerobes (1.6 per specimen). Anaerobic bacteria alone were present in 13 (16 per cent) of 83 specimens from abdominal abscesses, aerobes alone in two (2 per cent) and mixed flora in 68 (82 per cent). A total of 235 bacterial isolates were recovered in abdominal abscesses--128 anaerobes (1.5 per specimen) and 107 aerobes (1.3 per specimen). Anaerobic bacteria alone were present in 11 (12 per cent) of 89 specimens from abdominal wounds, aerobic only in ten (11 per cent) and mixed flora in 68 (76 per cent). A total of 258 isolates were recovered (2.9 per specimen)--137 anaerobes (1.5 per specimen) and 121 aerobes or facultatives (1.4 per specimen). The predominant aerobes and facultatives in abdominal infections were Escherichia coli and Streptococcus species. The predominant anaerobes were Bacteroides, Peptostreptococcus and Clostridium species. Recovered were 334 isolates of the Bacteroides fragilis group--222 in peritoneal cultures, 63 in abscesses and 49 in wounds. Of the B. fragilis group, B. fragilis accounted for 129 (58 per cent) of isolates in peritoneal aspirates, 45 (75 per cent) in aspirates from abscesses and 30 (61 per cent) in wounds. Results from this study demonstrate the polymicrobial aerobic and anaerobic cause and importance of all members of the B. fragilis group in intra-abdominal postsurgical infections.