Anaerobic infections in man are most commonly caused by nonsporing organisms. Such organisms occur naturally as commensals in the oropharynx, the female genital tract and the large bowel — where they constitute the predominant flora. From their normal habital these organisms may invade adjacent tissues which are debilitated or the seat of some pathological change.
With the appreciation of the clinical significance of anaerobic bacteria came the need for appropriate treatment. Many antimicrobial agents have been tried. Penicillin has been used with success in the treatment of orofacial sepsis and pleuropulmonary infection, but is inactive against Bacteroides fragilis which produces an effective β-lactamase. Tetracycline resistant organisms appear to have increased, and erythromycin has not found favour in the treatment of anaerobic sepsis. Chloramphenicol is active against almost all anaerobes, but its side effect as a bone marrow depressant must be borne in mind. Clindamycin is effective, but the possible development of pseudomembranous colitis must be considered. Metronidazole is at present used with success in a variety of anaerobic infections. The development of β-lactamase inhibiting agents, such as clavulanic acid, may indicate future trends in the chemotherapy of these infective conditions.
The antimicrobial agents currently in use for the treatment of anaerobic sepsis include penicillin, metronidazole, clindamycin, and cefoxitin, a modified form of a member of a new family of β-lactam antibiotics — the cephamycins.