In vitro activity of ABT-773 versus macrolides and quinolones against resistant respiratory tract pathogens

ABT-773, a novel ketolide, was compared to erythromycin, azithromycin, clar ithromycin, ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin, gatifloxa cin, and gemifloxacin against antibiotic-resistant strains recently isolate d from patients with respiratory tract infections. MICs were determined by agar dilution using standard NCCLS methodology. ABT-773 (MIC90 0.06 mg/L) w as more active than the macrolides (MIC90 greater than or equal to 2 mg/L) and fluoroquinolones (MIC90 greater than or equal to 0.5 mg/L) against peni cillin-resistant Streptococcus pneumoniae. The fluoroquinolones were the mo st active agents tested against P-lactamase-positive Haemophilus influenzae (MIC90 less than or equal to 0.01-0.06 mg/L), against which ABT-773 (MIC90 4 mg/L) was comparable to azithromycin and two- and four-fold more active than erythromycin and clarithromycin, respectively. Against beta -lactamase positive Moraxella catarrhalis, the activity of ABT-773 (MIC90 0.06 mg/L) was comparable to gemifloxacin, trovafloxacin, levofloxacin, and ciprofloxa cin (MIC90 0.03-0.06 mg/L) and 4- to eightfold greater than that of clarith romycin, gatifloxacin, and erythromycin. These data suggest ABT-773 could b e a valuable compound for the treatment of respiratory tract infections, in cluding those resistant to usual oral therapy. (C) 2001 Elsevier Science In c. All rights reserved.