Comparative In Vitro Activity of Gatifloxacin Against Stenotrophomonas maltophilia and Burkholderia Species Isolates Including Evaluation of Disk Diffusion and E Test Methods

Abstract

The in vitro activity of gatifloxacin, a new fluoroquinolone, was compared to that of five other fluoroquinolones against 105 Stenotrophomonas maltophilia isolates and 52 Burkholderia spp. isolates. The gatifloxacin MICs were determined using the broth microdilution method and the E test (AB Biodisk, Sweden); these methods were compared for test accuracy, and 5 microg disk zone diameters were compared for interpretive accuracy using the standardized disk diffusion method. In terms of potency, gatifloxacin was most similar to sparfloxacin and trovafloxacin against Stenotrophomonas maltophilia (MIC50, 0.5-1 mg/l) and Burkholderia spp. (MIC50, 1-2 mg/l). This activity was greater than that of ciprofloxacin, levofloxacin or ofloxacin (MIC50, > or = 2 mg/l) against Stenotrophomonas maltophilia isolates but comparable to that of levofloxacin against the Burkholderia spp. (60% susceptible at < or = 2 mg/l). The E test results compared well with the reference dilution test results (81-97% at +/- 1 log2 dilution). The disk diffusion test using previously suggested breakpoints for other bacteria (> or = 18 mm or < or = 2 mg/l for susceptible and < or = 14 mm or > or = 8 mg/l for resistant) also performed well, at > 90% categorical agreement. The activity of gatifloxacin is comparable to that of other newer quinolones against isolates of Stenotrophomonas maltophilia and Burkholderia spp., and susceptibility testing using simple qualitative and quantitative methods appears to function well with these drug/organism combinations.

Risk Factors for Late‐Onset Nosocomial Pneumonia Caused byStenotrophomonas maltophiliain Critically Ill Trauma Patients

“…Ticarcillin-clavulanate and ceftazidime are potential alternatives, but, because only ∼50% of S. maltophilia isolates are susceptible to these drugs, their ability to provide adequate empiric coverage is limited [31,32]. In vitro data suggest that the newer fluoroquinolones and doxycycline may be useful; however, clinical experience with these agents is sparse [33,34]. Given the relative lack of agents that have significant activity against S. maltophilia, it is not surprising that the majority of SM-VAP patients in our study did not receive adequate empiric antibiotic therapy.…”

Antimicrobial susceptibility patterns of unusual nonfermentative gram-negative bacilli isolated from Latin America: report from the SENTRY Antimicrobial Surveillance Program (1997-2002)

“…These fluoroquinolones have shown good activity against Burkholderia spp. in previous studies (Biedenbach et al 1999, Dawis et al 2003.…”

In Vitro Killing Effect of Moxifloxacin on Clinical Isolates of Stenotrophomonas maltophilia Resistant to Trimethoprim-Sulfamethoxazole

“…Trimethoprimsulfamethoxazole is considered the treatment of choice (2), but resistant isolates emerge (8). Although newer fluoroquinolones have been shown to possess a considerable in vitro inhibitory effect on that species (3,10), studies involved only isolates susceptible to co-trimoxazole. The present study focused on the in vitro killing effect of moxifloxacin on genetically distinct isolates of S. maltophilia resistant to co-trimoxazole.…”