Most gastrointestinal infections secondary to the use of antimicrobial agents that have been documented are related to overgrowth of Clostridium diff… - Sydney M. Finegold

There is an impressive incidence of anaerobes in major infections involving the lung and pleural space, intra-abdominal sites, and the female genital tract. Almost all anaerobic infections are endogenous in origin. Therapy consists of making the environment such that anaerobes find it difficult to proliferate, checking the spread of anaerobes into healthy tissues, and neutralizing the toxins of anaerobes.

Anaerobes are prevalent on all mucosal surfaces and virtually all anaerobic infections are endogenous. Two thirds of anaerobic infections involve five anaerobic organisms or groups—the Bacteroides fragilis group, the Bacteroides melaninogenicus-Bacteroides asaccharolyticus group, Fusobacterium nucleatum, the anaerobic cocci, and Clostridium perfringens. Conditions that lower the oxidation-reduction potential and disrupt the mucosal surface (eg, vascular problems, malignant neoplasms, and surgery) lead to infection with anaerobes. Clues to anaerobic infection include foul odor, gas, tissue destruction, underlying malignant neoplasms, and the unique appearance of certain anaerobes on Gram's stain. Specimens must be collected to avoid normal flora and transported to the laboratory under anaerobic conditions. Therapy involves surgical débridement and drainage and the use of various antimicrobial agents. Antimicrobial agents must be used for extended periods to avoid relapse.

The commonly used drugs that have a major effect on the colonic flora are ampicillin, cefoperazone, clindamycin and oral neomycin or kanamycin, used together with either tetracycline, erythromycin or metronidazole.