Antimicrobial Activities of Gatifloxacin against Nosocomial Isolates of Stenotrophomonas maltophilia Measured by MIC and Time-Kill Studies

We determined in vitro activities of gatifloxacin and seven other drugs against 100 isolates of Stenotrophomonas maltophilia using the agar gradient diffusion (Etest) method. Percentages of susceptible isolates were as follows: trimethoprim-sulfamethoxazole, 90%; gatifloxacin, 71%; levofloxacin, 57%; ticarcillin-clavulanic acid, 54%; ceftazidime, 49%; ciprofloxacin, 29%; cefepime, 21%; and piperacillin-tazobactam, 20%. Time-kill studies of three isolates indicated that gatifloxacin was bactericidal at times as early as 3 h of incubation when tested at concentrations equivalent to twice the MIC (two isolates) and 4 times the MIC (one isolate).