Contemporary re-evaluation of the activity and spectrum of grepafloxacin tested against isolates in the United States.

Grepafloxacin potency and spectrum of activity were re-evaluated against contemporary pathogens collected from clinical infections in 2001-2002. A total of 995 isolates were tested for grepafloxacin by the reference agar dilution method and these results were compared to those of 25 other antimicrobial agents. Grepafloxacin activity remained comparable to that of ciprofloxacin, levofloxacin and gatifloxacin against Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae (MIC(90), 0.03-2 microg/ml; 0.0-7.7% resistance rates). For Pseudomonas aeruginosa, grepafloxacin was active against ciprofloxacin-susceptible (MIC(90), 2 microg/ml), but not against ciprofloxacin-resistant (MIC(90), >8 microg/ml) isolates. Against methicillin-susceptible Staphylococcus aureus, grepafloxacin susceptibility rate was 91.4%, equal to that of levofloxacin. None of the fluoroquinolones showed reasonable activity against methicillin-resistant staphylococci. Gatifloxacin and grepafloxacin had the same MIC(90) against beta-hemolytic streptococci (0.25 microg/ml) and penicillin-susceptible Streptococcus pneumoniae (0.25 microg/ml). Grepafloxacin and other fluoroquinolone activities were not influenced by penicillin resistance in S. pneumoniae. Grepafloxacin was very active against Haemophilus influenzae (MIC(90), 0.03 microg/ml), Moraxella catarrhalis (MIC(90), 0.03 microg/ml) and Legionella spp. (MIC(90), 0.5 microg/ml). These results on recently isolated organisms indicate that grepafloxacin has a sustained potency and spectrum against most clinically important and indicated pathogens.