• Vol. 36 No. 10, 807–810
  • 15 October 2007

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 vitroactivity 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 ≥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.

Tigecycline is a recently developed antibiotic that belongs to the glycylcycline class, which is a novel analogue of the tetracyclines. Tigecycline is reported to have excellent in vitro activity against most Enterobacteriaceae,1 although minimum inhibitory concentrations (MICs) are higher against Proteus mirabilis, P. vulgaris, Morganella morganii, and Providencia spp.2 Based on in vitro data, tigecycline is also active against Acinetobacter spp., but not against Pseudomonas aeruginosa.

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