In vitro activity of tigecycline against Stenotrophomonas maltophilia tested by time-kill studies
Abstract number: P1042
Aracil B., Gil Y., Gómez-Garcés J.L.
Introduction: The pharmacodynamic activity of tigecycline for Stenotrophomonas maltophilia are not defined.
Methods: Antimicrobial susceptibility testing of 80 clinical isolates from 1996 to 2006 was performed by agar dilution. Tigecycline concentrations were serially increased in time-kill studies with representative strains of different susceptibility, MIC of 0.5 mg/liter, and MIC of 8 mg/liter. The in vitro susceptibility of the strains was tested by time-kill studies in duplicate. From an initial inocule gives of 0.5 105 ufc/ml serially counting were done at 0, 2, 4, 6, 24, and 48 h.
Results: Eighty isolates were tested and were found to have the following antimicrobial susceptibility profiles: tigecycline, MIC50 of 2 mg/liter and MIC90 of 4 mg/liter; ciprofloxacin, MIC50 of 1 mg/liter and MIC90 of 8 mg/liter; colistin, MIC50 of 16 mg/liter and MIC90 of 32 mg/liter; gentamycin, MIC50 of 16 mg/liter and MIC90 of 32 mg/liter; ceftazidime MIC50 of 32 mg/liter and MIC90 of 32 mg/liter; piperacillin-tazobactam MIC50 of 128 mg/liter and MIC90 of 128 mg/liter, and imipenem, MIC50 of 32 mg/liter and MIC90 of 32 mg/liter. According to FDA breakpoints 81.2% of the isolates were susceptible to tigecycline, 12% of the isolates were considered intermediate and 3 isolates were resistant. A reduction of 0, 0, 1, 2.2, 3, and 3 log10 was produced at 0, 2, 4, 6, 24, and 48 h., respectively.
Conclusion: Concentration escalation studies with tigecycline revealed a maximal killing effect near the MIC with no additional extent or rate of killing at concentrations 2× to 4× the MIC for tigecycline with independence of the categorisation were susceptible or resistant.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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