Surveillance of susceptibility of 2,228 clinical isolates to gatifloxacin and various antimicrobial agents

In order to examine the activity of fluoroquinolone antibiotics against fresh clinical isolates, we conducted a survey on the susceptibility of 2,228 strains of four gram-positive bacteria and eight gram-negative bacteria to 11 antimicrobials including gatifloxacin (GFLX), during the period from November 2002 to March 2003. These were isolated from sputum, urine, sinus discharge, otorrhea, and middle ear discharge obtained from 15 facilities in Japan. All the isolates were tested in accordance with the National Committee for Clinical Laboratory Standards. The MIC₉₀ of GFLX against penicillin-resistant Streptococcus pneumoniae (PRSP) was 0.5 μg/mL and its sensitivity rate was also satisfactory at 100%. As in the penicillin-susceptible strains, GFLX exhibited strong antimicrobial activity and good sensitivity against PRSP. MIC₉₀ of GFLX against Haemophilus influenzae was as low as 0.03 μg/mL and its sensitivity was 99%. The MIC₉₀ of GFLX against Escherichia coli stood at 8 μg/mL. The MIC₉₀ values of fluoroquinolone antimicrobials against Neisseria gonorrhoeae ranged from 2 μg/mL to 16 μg/mL and their sensitivity rates surpassed 90%. On an average, this survey found that fluoroquinolone antimicrobials were very active against Klebsiella pneumoniae, including S. pneumoniae, H. influenzae, and Moraxella catarrhalis. Additionally, GFLX, among others, demonstrated particularly strong bactericidal activity against S. pneumoniae without suffering a decline in drug sensitivity. Consequently, GFLX could be one of the clinically useful drugs for respiratory infections. On the other hand, it is now evident that E. coli, Enterococci, Pseudomonas aeruginosa, and N. gonorrhoeae have developed more resistance to fluoroquinolone antimicrobials as compared to their previous susceptibility.