Comparative In Vitro Activities of ABT-773 against 362 Clinical Isolates of Anaerobic Bacteria

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Abstract
The activity of ABT-773, a novel ketolide antibiotic, against clinical isolates of anaerobic bacteria was determined and compared to the activities of other antimicrobial agents. MICs at which 90% of isolates were inhibited (MIC 90 s) were ≤0.06 μg/ml for Actinomyces spp., Clostridium perfringens , Peptostreptococcus spp., Propionibacterium spp., and Porphyromonas spp. The MIC 50 s and MIC 90 s were ≤0.06 and >32 μg/ml, respectively, for Eubacterium spp., Lactobacillus spp., Clostridium difficile , and Clostridium ramosum. The MIC 90 for Bilophila wadsworthia , Bacteroides ureolyticus, and Campylobacter gracilis was 1 μg/ml, and that for Prevotella bivia and other Prevotella spp. was 0.5 μg/ml. The MIC 90 for Fusobacterium nucleatum was 8 μg/ml, and that for Fusobacterium mortiferum and Fusobacterium varium was >32 μg/ml . The MIC 90 s for the Bacteroides fragilis group were as follows: for B. fragilis , 8 μg/ml; for Bacteroides thetaiotaomicron , Bacteroides ovatus , Bacteroides distasonis , and Bacteroides uniformis , >32 μg/ml; and for Bacteroides vulgatus , 4 μg/ml. Telithromycin MICs for the B. fragilis group were usually 1 to 2 dilutions higher than ABT-773 MICs. For all strains, ABT-773 was more active than erythromycin by 4 or more dilutions, and for some strains this drug was more active than clindamycin.