Antibacterial Activity of 4th Generation Fluoroquinolones Against Ocular Pathogens

Abstract

Abstract: : Purpose: To compare the antibacterial activity of the 4^th generation fluoroquinolones gatifloxacin and moxifloxacin against typical ocular pathogens. Methods: Minimal inhibitory concentrations (MIC) of gatifloxacin and moxifloxacin were performed in microtiter format in triplicate as per NCCLS guidelines. The following clinical ocular isolates were tested: Bacillus cereus, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Enterococcus faecalis, Streptococcus pyogenes, Streptococcus viridans, Pseudomonas aeruginosa, Serratia marcescens, Klebsiella pneumoniae, Enterobacter aerogenes, Nocardia asteroides, and Mycobacterium chelonae. Results: Gatifloxacin and moxifloxacin exhibited similar activities against the following Gram-positive isolates: S. epidermidis, S. aureus, S. pneumoniae, S. pyogenes, B. cereus, and E. faecalis. MIC values for these isolates ranged from 0.08 µg/ml to 0.57 µg/ml, and were comparable to previously published values for isolates recovered from systemic infections. The mean MIC of gatifloxacin for S. viridans was 0.22 µg/ml, compared with 0.73 µg/ml for moxifloxacin. The mean MIC of gatifloxacin for P. aeruginosa was 1.28 µg/ml, as compared to 2.60 µg/ml for moxifloxacin. Mean MIC values of gatifloxacin against K. pneumoniae and E. aerogenes were 4- to 6-fold lower than that of moxifloxacin. Both fluoroquinolones achieved similar activities against S. marcescens. Mean MIC values of gatifloxacin against N. asteroides and M. chelonae were 4-fold lower than that of moxifloxacin. Conclusions: Gatifloxacin and moxifloxacin displayed similar activities in vitro against most Gram-positive ocular pathogens and S. marcescens. Compared with that of moxifloxacin, gatifloxacin MIC values were 2-fold lower against P. aeruginosa, 3-fold lower against S. viridans, 4-fold lower against N. asteroides and M. chelonae, and 4- to 6- fold lower against K. pneumoniae and E. aerogenes.

Keywords: antibiotics/antifungals/antiparasitics • bacterial disease • clinical laboratory testing