In vitro activity of tigecycline against Acinetobacter baumannii tested by time-kill studies

Abstract number: P1043

Aracil B., Gil Y., Gómez-Garcés J.L.

Introduction: Tygecicline is a new expanded broad spectrum antibiotic against Acinetobacter baumannii, its pharmacodynamic activity is not well defined yet.

Methods: Antimicrobial susceptibility testing of 85 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: MICs of 0.5 mg/l, 1 mg/l., 2 mg/l, and 4 mg/l. 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-five isolates were tested and were found to have the following antimicrobial susceptibility profiles: tigecycline, MIC50 of 0.25 mg/liter and MIC90 of 2 mg/liter; ciprofloxacin, MIC50 of leqslant R: less-than-or-eq, slant0.25 mg/liter and MIC90 of 8 mg/liter; colistin, MIC50 of 1 mg/liter and MIC90 of 2 mg/liter; gentamycin, MIC50 of leqslant R: less-than-or-eq, slant1 mg/liter and MIC90 of 32 mg/liter; ceftazidime MIC50 of 8 mg/liter and MIC90 of 32 mg/liter; piperacillin-tazobactam MIC50 of 32 mg/liter and MIC90 of 128 mg/liter, and imipenem, MIC50 of leqslant R: less-than-or-eq, slant1 mg/liter and MIC90 of 32 mg/liter. According to FDA breakpoints 96.5% of the isolates were susceptible to tigecycline. A reduction of 0, 0, 0, 1.2, 3.5, and 3.5 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 for the susceptible and intermediate strains.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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