Susceptibility of multi-resistant Gram-negative bacilli in Singapore to tigecycline as tested by agar dilution.

INTRODUCTION Tigecycline is an antibiotic belonging to the glycylcycline class with in vitro activity against most Gram-negative bacteria, other than Pseudomonas aeruginosa. This study investigated the in vitro activity of tigecycline against multi-resistant isolates of Enterobacteriaceae and Acinetobacter spp. isolated from clinical specimens in Singapore. MATERIALS AND METHODS Minimum inhibitory concentrations (MICs) to tigecycline were determined for 173 isolates of multi-resistant Escherichia coli, Klebsiella spp., Enterobacter spp. and Acinetobacter spp. using agar dilution. RESULTS The MIC required to inhibit the growth of 90% of organisms varied from 0.5 to 4 mg/L for the study isolates. Based on a resistance breakpoint of >or=8 mg/L, resistance rates varied from 0% to 9%. CONCLUSIONS Tigecycline demonstrates good in vitro activity against multi-resistant strains of Enterobacteriaceae, with more variable activity against multi-resistant strains of Acinetobacter spp.