Background: The Tigecycline Evaluation and Surveillance Trial (TEST) is a global antimicrobial susceptibility surveillance study which has been ongoing since 2004. This report examines the in vitro activity of tigecycline and comparators against clinically important pathogens collected globally between 2004 and 2013.
Methods: Antimicrobial susceptibility was determined using guidelines published by the Clinical and Laboratory Standards Institute. The Cochran Armitage Trend Test was used to identify statistically significant changes in susceptibility between 2004 and 2013.
Results: Among the Enterobacteriaceae susceptibility was highest to the carbapenems [imipenem 97.1% (24,655/25,381), meropenem 97.0% (90,714/93,518)], tigecycline (97.0%, 115,361/118,899) and amikacin (96.9%, 115,200/118,899). Against Acinetobacter baumannii the highest rates of susceptibility were for minocycline (84.5%, 14,178/16,778) and imipenem (80.0%, 3,037/3,795). The MIC90 for tigecycline was 2 mg/L. 40% (6,743/16,778) of A. baumannii isolates were multidrug-resistant. Enterococci were highly susceptible to tigecycline and linezolid (>99%); vancomycin resistance was observed among 2% of Enterococcus faecalis (325/14,615) and 35% of Enterococcus faecium (2,136/6,167) globally. 40% (14,647/36,448) of Staphylococcus aureus were methicillin-resistant while 15% (2,152/14,562) of Streptococcus pneumoniae were penicillin-resistant. Against S. aureus and S. pneumoniae susceptibility to linezolid, vancomycin, and tigecycline was ≥99.9%. Globally, 81% (331/410) of statistically significant susceptibility changes during the study period were decreases in susceptibility.
Conclusions: Amikacin, the carbapenems, and tigecycline were active against most gram-negative pathogens while linezolid, tigecycline, and vancomycin retained activity against most gram-positive pathogens collected in TEST during 2004-2013.