21st European Congress of Clinical Microbiology and Infectious Diseases

Antimicrobial susceptibility trends of Enterobacteriaceae from intra-abdominal infections in Europe: SMART 20022010

Abstract number: P565

Badal R., Hawser S., Bouchillon S., Hoban D., Hackel M., Johnson A.

Objectives: The Study for Monitoring Antimicrobial Resistance Trends (SMART) is a global longitudinal surveillance study that has tracked activity of ertapenem and other drugs used to treat intra-abdominal infections (IAI) since 2002. This report focuses on trends in susceptibility of Enterobacteriaceae over 9 years in Europe.

Methods: 86 hospitals in 15 European countries each collected up to 100 consecutively isolated Gram-negative aerobic bacteria per year from IAI. From 2002–2007, each site did susceptibility testing using MicroScan broth microdilution panels, following Clinical and Laboratory Standards Institute and MicroScan procedures and quality control. From 2008–2010 all susceptibility testing was done at a central lab (IHMA, Inc.), also using MicroScan panels. Minimum inhibitory concentrations (MICs) were interpreted using EUCAST guidelines. MIC frequency distributions were analysed for trends using Spearman's correlation coefficient, and geometric mean (GM) MICs calculated. Percent susceptibility from 2002 and 2010 was compared using Fisher's exact test. Only drugs tested all 9 years of the study were evaluated.

Results: MICs of all drugs showed statistically significant (p < 0.0001) changes from 2002–2010: amikacin's GM MIC declined, but all other drugs increased. Percent susceptible values declined significantly (p < 0.05) from 2002–2010 except for ertapenem, imipenem, and amikacin. The table below compares GM MICs in 2002 and 2010 for the 8 study drugs:

Conclusions: Although all drugs had statistically significant changes in MIC values over the course of the study, 3 (ertapenem, imipenem, and amikacin) did not show significant changes in their percent susceptible values, with all remaining >94% in 2010. The other 5 drugs had significantly reduced levels of susceptibility. Among the drugs studied, ertapenem, imipenem, and amikacin are the least affected by extended-spectrum b-lactamases, and the loss of activity of the other study drugs is probably due largely to increases in ESBL-producing Enterobacteriaceae in Europe that have been documented in numerous reports.