Nationwide surveillance in Taiwan of the in-vitro activity of tigecycline against clinical isolates of Gram-positive cocci

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 in Taiwan. This study, part of TIST-2006 study, aimed to compare the in-vitro activity of tigecycline against clinical isolates of Gram-positive bacteria. A total of 805 isolates of Gram-positive bacteria were collected from patients treated at 20 teaching hospitals. Minimum inhibitory concentrations (MICs) of tigecycline for these isolates were determined by the broth microdilution method according to the guidelines of the Clinical and Laboratory Standards Institute, and by the Etest as per the manufacturer's instructions. Susceptibility results were interpreted by the MIC criteria recommended by the US FDA. Agreement between the two methods was low: 80.7% for methicillin-resistant Staphylococcus aureus (MRSA), 27.2% for Streptococcus pneumoniae, 22.8% for other Streptococcus spp., and 30.8% for vancomycin-resistant E. faecium (VRE). There were no very major or major errors noted. Tigecycline exhibited excellent in-vitro activity against Gram-positive cocci, including MRSA, VRE, S. pneumoniae and other Streptococcus spp. isolates in Taiwan. Correlation between MIC values determined using the broth microdilution and Etest methods for these organisms was poor.