Antibiotic resistance in anaerobic bacteria: molecular biology and clinical aspects.

The patterns of antibiotic susceptibility among anaerobes isolated in the United States during the past 14 years were reviewed. Resistance to the tetracyclines, the penicillins, clindamycin, and other antibiotics has emerged among strains of Bacteroides, Clostridium, and anaerobic cocci. Genetic transfer of antibiotic resistance has been documented in anaerobic environments. Inter- and intrageneric transfer by conjugation and transformation has been described. Plasmids have been identified in anaerobes, and conjugal transfer of antibiotic resistance has been reported. The biochemical mechanisms of antibiotic resistance in anaerobes are similar to those described for aerobes. There are some differences in drug transport and inhibitory actions. Antibiotic resistant anaerobes have been isolated from patients participating in large comparative studies of anaerobic infections involving abdominal, pelvic, and pleuropulmonary sites, but instances in which treatment has failed as a result of resistance have not been found. Reports describing small numbers of patients or individual cases have documented the failure of therapy in clinical and laboratory infections caused by both sensitive or resistant anaerobic bacteria. Patterns of antibiotic susceptibility among clinically important anaerobes need to be monitored periodically in several geographic regions.