Comparison of ESBL rates and susceptibility of E. coli from IAI in the USA, Canada, and Mexico 2009-2013
Background: Extended-spectrum β-lactamase (ESBL) producing E. coli are multi-drug resistant and pose therapeutic challenges worldwide. This report from the Study for Monitoring Antimicrobial Resistance Trends (SMART) compares ESBL rates and susceptibility of E. coli from IAI from the USA, Canada, and Mexico in 2009-2013.
Methods: 44 laboratories (28 USA, 12 Canada, 4 Mexico) each collected up to 100 consecutive gram-negative organisms from IAI each year; 5,183 of 12,421 (42%) were E. coli. Susceptibility was determined using CLSI broth microdilution methods and breakpoints. Trends in ESBL rates were assessed with the Cochran-Armitage test.
Results: From 2009-2013, the proportion of ESBL+ E. coli showed significant increasing trends in all three countries. Susceptibility of selected drugs in 2013 (values ≥90% are shaded) and ESBL rates from 2009-2013 are shown below:
Sensitivity analysis for the USA using only the 13 sites that submitted isolates in all 5 years confirmed the increasing ESBL rates (6, 6, 10, 6, and 14% in the years 2009-2013); however, a similar analysis for Canada did not find a significant trend (in 5 of 12 sites) in part due to a larger drop in 2013 than in the full analysis (9, 8, 11, 19, 10%). All 4 Mexican sites participated in all 5 years.
· E. coli ESBL rates were much higher in Mexico, and although all 3 countries showed increasing trends in the full analysis, they appear to be leveling off in Canada and Mexico.
· In 2013, only AMK, ETP and IPM showed %S >90% in all 3 countries against E. coli. The much higher ESBL rate in Mexico corresponded to dramatically lower susceptibility rates than North America to most other drugs.
· Despite having significantly lower ESBL+ E. coli rates than Mexico, the US and Canada must take steps to contain further spread of these organisms, and Mexico itself must continue efforts (such as restricting fluoroquinolone use) to address this situation in which ESBL+ is the predominant phenotype among E. coli.
Merck: Independent Contractor, Consulting fee
M. Hackel, Merck: Independent Contractor, Consulting fee
S. Bouchillon, Merck: Independent Contractor, Consulting fee
A. Johnson, Merck: Independent Contractor, Consulting fee
D. Hoban, Merck: Independent Contractor, Consulting fee
D. Sahm, Merck: Independent Contractor, Consulting fee