Antimicrobial therapy of anaerobic infections, 1991

Most anaerobic infections are polymicrobial and must be treated with agents active against a variety of both aerobic and anaerobic bacteria. Antimicrobial therapy is used both to contain infections and to treat those that have not been contained (bacteremia). Bacterial resistance, especially to penicillins and tetracyclines, but also to newer agents of other classes, continues to increase and often requires treatment with more than one drug. Combination therapy is also frequently necessary in serious infections, and is indicated for empiric management before receiving results of in vitro microbiology laboratory tests. However, recent results suggest that monotherapy for anaerobic infections may dominate in the future, although combination therapy has been the mainstay of antimicrobial therapy. Selection of an agent must take into account the site of infection and thus the bacteria most likely to be found. It should be kept in mind that in vitro susceptibility is not the only determinant of antimicrobial effectiveness. The pharmacology of the drug--absorption, distribution, concentration in body fluids and tissues, and metabolism--also plays an important role. Finally, the nature and severity of the underlying illness, the toxicity of the agent, and costs must be considered.