Comparative in vitro activities of ABT-773 against aerobic and anaerobic pathogens isolated from skin and soft-tissue animal and human bite wound infections

We studied the comparative in vitro activities of ABT-773, a new ketolide, against 268 aerobic and 148 anaerobic recent isolates from clinical bites using an agar dilution method and inocula of 10(4) CFU/spot for aerobes and 10(5) CFU for anaerobes. The following are the MIC ranges and MICs at which 90% of Isolates are inhibited (MIC(90)s) of ABT-773 for various isolates, respectively: Pasteurella multocida and Pasteurella septica, 0.125 to 2 and 1 mu g/ml; other Pasteurella species, 0.125 to 1 and 0.5 mu g/ml; Corynebacteriun spp., 0.015 to 0.06 and 0.015 mu g/ml; Staphylococcus aureus, 0.03 to 0.06 and 0.06 mu g/ml; coagulase-negative staphylococci, 0.015 to >32 and 32 mu g/ml; streptococci, 0.015 to 0.03 and 0.03 mu g/ml; Eikenella corrodens, 0.25 to 1 and 1 mu g/ml; and Bergeyella zoohelcum, 0.03 to 0.25 and 0.06 mu g/ml. For anaerobes the MIC ranges and MIC(90)s of ABT-773 were as follows, respectively: Prevotella heparinolytica, 0.06 to 0.125 and 0.125 mu g/ml; Prevotella spp., 0.015 to 0.125 and 0.06 mu g/ml; Porphyromonas spp., 0.015 to 0.03 and 0.015 mu g/ml; Fusobacterium nucleatum, 0.5 to 8 and 8 mu g/ml; other Fusobacterium spp., 0.015 to 8 and 0.5 mu g/ml; Bacteroides tectum, 0.015 to 0.5 and 0.06 mu g/ml; and Peptostreptococcus spp,, 0.015 to 0.25 and 0.03 mu g/ml. ABT-773 was more active than all macrolides tested against S. aureus, E. corrodens, and anaerobes, but all compounds were poorly active against F. nucleatum, The activity of ABT-773 was within 1 dilution of that of azithromycin against Pasteurella spp., and ABT-773 was four- to eightfold more active than clarithromycin against Pasteurella spp. ABT-773 may offer a therapeutic alternative for bite wound infections.