Antimicrobial therapy for anaerobic infections

Our increasing understanding of anaerobes and the infections they cause has reaffirmed that benzyl-penicillin is a useful agent when B. fragilis group organisms can be ruled out. At the same time, however, we have also learned that the number of instances in which penicillin-resistant bacteroides can be ruled out seems to be diminishing. For the most serious anaerobic infections, the clinician must turn to an agent such as chloramphenicol, clindamycin, or metronidazole. As a group, these drugs are the most reliably effective against clinically significant B. fragilis and most other anaerobes; gaps in their spectrum can be covered with benzyl-penicillin. A major drawback with chloramphenicol, in particular, remains its potential toxicity, a feature that underscores the importance of matching the antimicrobial weapon to the target. The less consistently reliable agents tend to be the less potentially toxic; they should be used if the anaerobic infection is judged not serious or life threatening. The more potent, potentially more toxic drugs should be used when life is in danger.