The antibiotic susceptibilities of Xanthomonas maltophilia and their relation to clinical management.

An increase in recovery of Xanthomonas maltophilia from clinical specimens at our institutions prompted, amongst other measures, an investigation of the antibiotic susceptibility patterns of the organism. Fifty-five consecutive first isolates of Xanthomonas maltophilia were obtained and antimicrobial susceptibility tests were carried out by the agar dilution method. Trimethoprim/sulfamethoxazole was the most active antimicrobial agent (94% susceptible), with 71% susceptible to ticarcillin/clavulanic acid, 56% susceptible to ciprofloxacin and 49% susceptible to ceftazidime. Amoxycillin/clavulanic acid and imipenem were inactive (0% susceptible), while aminoglycosides were effective against only 7% of isolates. Potentiation was observed with both the combination of trimethoprim and sulfamethoxazole and the combination of ticarcillin and clavulanic acid. Familiarity with the antibiotic susceptibility pattern of Xanthomonas maltophilia as well as the potential shortcomings of the in vitro susceptibility data are important in the effective clinical management of Xanthomonas maltophilia infections.