Surveillance of susceptibility of clinical isolates to gatifloxacin and various antimicrobial agents

In order to continually examine the susceptibility of clinical isolates against gatifloxacin (GFLX), we conducted a surveillance measuring that of 2,508 strains of four gram-positive and seven gram-negative pathogens to 12 antimicrobials including GFLX, during the period from November 2004 to March 2005 following previous surveillance conducted in 2002. Tested pathogens were isolated from sputum, urine and sinus discharge obtained from 15 facilities throughout Japan. GFLX exhibited superior antibacterial activity against Streptococcus pneumoniae, comparison to other fluoroquinolones, by showing same MIG₅₀ and MIC₉₀ values of 0.25 μg/mL and a satisfactory susceptible rate at 96.5%. Antibacterial activity of GFLX was not influenced by the development of penicillin-resistance in S. pneumoniae. The MIC₉₀ values of fluoroquinolones against Haemophilus influenzae and Moraxella catarrhalis were commonly as low as 0.015 μg/mL to 0.03 μg/mL. The MIC₅₀ and MIC₉₀ values of GFLX against Escherichia coli and Enterococcus faecalis were 0.06 μg/mL-0.5,4 μg/mL and 8 μg/mL-16 μg/mL, respectively. The susceptible rate for fluoroquinolones were 83-67%. On an average, this surveillance indicated that fluoroquinolones kept strong antibacterial activities against H. influenzae and M. catarrhalis. Among others, GFLX has maintained strong antibacterial activity against S. pneumoniae as the MIC₉₀ value of 0.25 μg/mL was identical to that observed at the launch. It was thought that GFLX was the clinically useful drugs for empiric therapy against main pathogens of respiratory tract, otorhinolaryngology and urinary tract infections. While antibacterial activities of fluoroquinolones against E. coli and E. faecalis did not almost change from 2002 surveillance, it was thought the susceptibility needed to be examined continually in future.