SUSCEPTIBILITY TESTING OF ANAEROBIC-BACTERIA - THE STATE-OF-THE-ART

Demand for susceptibility testing of anaerobes has increased, but no c onsensus on procedure and interpretation has been achieved. The need f or reliable methods for testing anaerobic bacteria extends from small hospital laboratories to large research centers. Agar dilution testing is too costly and labor intensive for many clinical laboratories. Mic robroth dilution is more convenient; however, some fastidious anaerobe s do not grow well enough in this system, and the choice of antimicrob ial agents may not reflect the hospital formulary. Disapproval of the broth disk elution system leaves fewer options open to clinical labora tories and emphasizes the need for more convenient and reliable techni ques. Some newer methods are undergoing evaluation. Variables in susce ptibility testing of anaerobes include the media and methods used, org anisms chosen, breakpoints chosen, and endpoint determination. This la tter variable is probably the most problematic since no endpoint based on interaction of organism and antimicrobial agent rather than on sub jective observation has been defined. Also, clustering of MICs around the breakpoint may lead to significant variability in reported methods . A more accurate MIC measurement is needed. Adherence of laboratories to approved methods and careful reporting of methods and the interpre tive breakpoints would facilitate interlaboratory comparisons and the identification of emerging resistance.