Nationwide surveillance in Taiwan of the in-vitro activity of tigecycline against clinical isolates of extended-spectrum β-lactamase-producing Enterobacteriaceae

Tigecycline In-vitro Surveillance in Taiwan (TIST), initiated in 2006, is a nationwide surveillance programme designed to monitor longitudinally the in-vitro activity of tigecycline against commonly encountered resistant bacteria. This study compared the in-vitro activity of tigecycline against clinical isolates of resistant Gram-negative bacteria determined by the broth microdilution and Etest methods. A total of 622 isolates were collected from patients treated at 20 teaching hospitals. Tigecycline had excellent in-vitro activity against extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (N = 275) with MIC₉₀ 0.5 μg/mL and a 99.6% susceptibility rate, and also against ESBL-producing Klebsiella pneumoniae (N = 324) with MIC₉₀ 2 μg/mL and a 98.5% susceptibility rate. For ESBL-producing Proteus mirabilis (N = 15) the MIC₉₀ was 4 μg/mL with a 73.3% susceptibility rate. For ESBL-producing Klebsiella oxytoca (N = 8) the MIC₅₀ and MIC₉₀ were 0.5 and 1 μg/mL, respectively, with a 100% susceptibility rate. Limited agreement (<80%) was found between the broth microdilution and the Etest methods when determining the in-vitro activity of tigecycline against ESBL- producing K. pneumoniae and K. oxytoca.