EVALUATION OF THE ETEST FOR ANTIMICROBIAL SPECTRUM AND POTENCY DETERMINATIONS OF ANAEROBES ASSOCIATED WITH BACTERIAL VAGINOSIS AND PERITONITIS

One hundred ninety-seven anaerobic organisms (24 Gardnerella vaginalis, 16 Mobiluncus spp., 19 Peptostreptococcus spp., 20 Lactobacillus spp., 20 Prevotella bivia/disiens, 81 Bacteroides fragilis group, 12 Clostridium spp., and five Fusobacterium spp.) were processed by the Etest (AB Biodisk, Solna, Sweden) and a reference (Brucella blood agar) method against 10 antimicrobial agents. For the bacterial vaginosis-associated pathogens, the Etest was more reproducible and correlated acceptably with the reference agar test: within +/-1 log(2) dilution for 74.4% of Mobiluncus spp, to 96.0% for Peptostreptococcus spp. (all organisms, 83.4%). The quantitative correlation +/-2 log(2) dilution steps between test results was 94.3%. Results with B. fragilis group strains demonstrated 97.3% correlation (+/-2 log(2) dilution) with a trend toward slightly lower Etest minimum inhibitory concentrations for ampicillin-sulbactam, cefotaxime, imipenem, and clindamycin. The absolute qualitative interpretive agreement between Etest and the reference agar dilution method results was 94.4%, with only a 0.4% false-susceptible error rate. The Etest appears to be a very practical, quantitatively accurate, alternative procedure for clinical microbiology laboratories routinely testing the susceptibilities of anaerobes and, by these presented data, organisms associated with female tract infections.