Antimicrobial susceptibility testing of anaerobic bacteria

Antimicrobial therapy of anaerobic infections is usually predicted on the basis of known patterns of susceptibility of anaerobic bacteria to antimicrobial agents rather than on results of in vitro tests of individual isolates. Routine susceptibility testing of anaerobic bacteria is not recommended, but there are instances of serious infection, i.e., endocarditis, or specific infecting organisms, e.g., Bacteroides fragilis, when in vitro testing of the specific infecting organism is indicated. No standard method has yet been accepted. Methods presently recommended are agar dilution or broth dilution tests. Other methods currently being evaluated are agar (disc) diffusion, broth-disc, and simplified broth and agar dilution tests. The advantages and limitations of the various methods are discussed.