Antimicrobial susceptibility among Gram-positive and Gram-negative isolates collected in Europe between 2004 and 2010

Here we report on the in vitro activity of a suite of antimicrobial agents against Gram-negative and Gram-positive pathogens collected in Europe between 2004 and 2010 as part of the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.). Clinical and Laboratory Standards Institute (CLSI) broth microdilution methodologies were used to determine minimum inhibitory concentrations. CLSI interpretive criteria were applied for all antimicrobial agents to establish susceptibility; European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were used for tigecycline. In total, 46,921 Gram-negative and 19,174 Gram-positive isolates were included in this study. Extended-spectrum β-lactamases increased in proportion from 15.7% to 21.1% among Klebsiella pneumoniae and from 9.7% to 16.1% among Escherichia coli isolates between 2004–2007 and 2010. E. coli susceptibility decreased to most antimicrobials but it remained highly susceptible (>98%) to tigecycline and meropenem. Acinetobacter baumannii susceptibility also decreased to most agents. The proportion of meticillin-resistant Staphylococcus aureus (MRSA) decreased from 25.7% to 19.4% over the study period. Antimicrobial susceptibility has decreased among many of the pathogens observed in the T.E.S.T. surveillance study between 2004–2007 and 2010.