<abstract xmlns="http://www.w3.org/1999/xhtml"> Background: Minimum inhibitory concentration (MIC) breakpoints of selected cephalosporins and carbapenems against Enterobacteriaceae have been revised by major guidelines including CLSI and EUCAST mainly according to available pharmacokinetic/pharmacodynamic data. A decrease of breakpoint may obviate the need to detect specific resistance mechanisms such as extended-spectrum -lactamase (ESBL) and carbapenemase, which may be less correlated to treatment outcome than does the actual MIC of each agent.Objective: To analyze cephalosporin and carbapenem MIC distributions among ESBL-producing Enterobacteriaceae at a university hospital against revised interpretative breakpoints.Methods: MIC distributions of selected cephalosporins and carbapenems among 505 isolates of genotypically confirmed ESBL-producing Enterobacteriaceae were determined by E-testTM method and analyzed according to interpretative breakpoints comparing between CLSI and EUCAST guidelines.Results: ESBL-producing Enterobacteriaceae demonstrated a wide range of cephalosporin MIC (≤1 to ≥64). Up to 9.7% of isolates displayed MIC lower than a revised cephalosporin breakpoint. Most isolates remained susceptible to imipenem and meropenem while as high as 24.6% were not susceptible to ertapenem. Lowered breakpoints may result in a change in categorical interpretations.Conclusion: ESBL-producing isolates could be reported as susceptible to a cephalosporin with revised breakpoints although clinical use is uncertain. A higher proportion of isolates would be reported as nonsusceptible to cephalosporins or carbapenems with lowered breakpoints and thus increasing use of broadspectrum antimicrobial agents should be monitored. </abstract>

Background: Minimum inhibitory concentration (MIC) breakpoints of selected cephalosporins and carbapenems against Enterobacteriaceae have been revised by major guidelines including CLSI and EUCAST mainly according to available pharmacokinetic/pharmacodynamic data. A decrease of breakpoint may obviate the need to detect specific resistance mechanisms such as extended-spectrum -lactamase (ESBL) and carbapenemase, which may be less correlated to treatment outcome than does the actual MIC of each agent.Objective: To analyze cephalosporin and carbapenem MIC distributions among ESBL-producing Enterobacteriaceae at a university hospital against revised interpretative breakpoints.Methods: MIC distributions of selected cephalosporins and carbapenems among 505 isolates of genotypically confirmed ESBL-producing Enterobacteriaceae were determined by E-testTM method and analyzed according to interpretative breakpoints comparing between CLSI and EUCAST guidelines.Results: ESBL-producing Enterobacteriaceae demonstrated a wide range of cephalosporin MIC (≤1 to ≥64). Up to 9.7% of isolates displayed MIC lower than a revised cephalosporin breakpoint. Most isolates remained susceptible to imipenem and meropenem while as high as 24.6% were not susceptible to ertapenem. Lowered breakpoints may result in a change in categorical interpretations.Conclusion: ESBL-producing isolates could be reported as susceptible to a cephalosporin with revised breakpoints although clinical use is uncertain. A higher proportion of isolates would be reported as nonsusceptible to cephalosporins or carbapenems with lowered breakpoints and thus increasing use of broadspectrum antimicrobial agents should be monitored.

Effect of MIC interpretative breakpoint revision on cephalosporin and carbapenem susceptibility among ESBL-producing Enterobacteriaceae

Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700,

Asian Biomedicine

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Background: Minimum inhibitory concentration (MIC) breakpoints of selected cephalosporins and carbapenems against Enterobacteriaceae have been revised by major...

Effect of MIC interpretative breakpoint revision on cephalosporin and carbapenem susceptibility among ESBL-producing Enterobacteriaceae

Article Category: Original article

Published Online: Feb 04, 2017

Page range: 713 - 721

DOI: https://doi.org/10.5372/1905-7415.0605.112

Keywords
Breakpoint, carbapenem, cephalosporin, enterobacteriaceae, ESBL, MIC

© 2017

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Effect of MIC interpretative breakpoint revision on cephalosporin and carbapenem susceptibility among ESBL-producing Enterobacteriaceae

Article Category: Original article

Published Online: Feb 04, 2017

Page range: 713 - 721

DOI: https://doi.org/10.5372/1905-7415.0605.112

KeywordsBreakpoint, carbapenem, cephalosporin, enterobacteriaceae, ESBL, MIC

© 2017

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Keywords
Breakpoint, carbapenem, cephalosporin, enterobacteriaceae, ESBL, MIC