Antimicrobial Susceptibilities of Unique Stenotrophomonas maltophilia Clinical Strains

Susceptibility to 41 antimicrobials was studied with 99 Stenotrophomonas maltophilia strains, and different pulsed-field gel electrophoresis profiles were identified among 130 prospectively collected isolates. Moxalactam, doxycycline, minocycline, and clinafloxacin displayed the highest activity (≥98% susceptibility). Ticarcillin resistance (75%) was reverted by clavulanate in 25% of strains. Trimethoprim-sulfamethoxazole resistance was 26.2% (≥4 [trimethoprim]/76 [sulfamethoxazole] μg/ml) and dropped to 11.1% when an 8/152-μg/ml breakpoint was applied based on its bimodal MIC distribution. Resistance was lower when unique strains were considered, because clonal organisms contribute to resistance.