CLSI breakpoints for antibiotic susceptibility testing (AST) CLSI breakpoints, 2015 (3) Current MIC breakpoints (µg/mL) MIC interpretation1 Carbapenems Susceptible Intermediate Resistant Doripenem 2 ≤1 ≥4 Ertapenem 1 ≤0.5 ≥2 Imipenem 2 ≤1 ≥4 Meropenem 2 ≤1 ≥4 Current disk diffusion zone diameters (mm) Interpretation Carbapenems Susceptible Intermediate Resistant Doripenem 20-22 ≥23 ≤19 Ertapenem 19-21 ≥22 ≤18 Imipenem 20-22 ≥23 ≤19 Meropenem 20-22 ≥23 ≤19 1 Laboratories still using breakpoints before the June 2010 CLSI update should use the updated CLSI MIC cutoffs to determine reporting to public health, independent of the susceptibility interpretation (e. g., an isolate with an MIC of 8 to meropenem [“intermediate” by pre-2010 CLSI interpretation, but by CLSI guidelines starting in 2011] should still be reported to MDPH and submitted “resistant” for further evaluation). Many, if not most, ertapenem mono-resistant Enterobacteriaceae do not actually rule-in as CRE.
CLSI breakpoints for antibiotic susceptibility testing (AST) CLSI breakpoints, 2015 (3) Current MIC breakpoints (µg/mL) MIC interpretation1 Carbapenems Susceptible Intermediate Resistant Doripenem ≤1 2 ≥4 Ertapenem ≤0.5 1 ≥2 Imipenem ≤1 2 ≥4 Meropenem ≤1 2 ≥4 Current disk diffusion zone diameters (mm) Interpretation Carbapenems Susceptible Intermediate Resistant Doripenem ≥23 20-22 ≤19 Ertapenem ≥22 19-21 ≤18 Imipenem ≥23 20-22 ≤19 Meropenem ≥23 20-22 ≤19 1 Laboratories still using breakpoints before the June 2010 CLSI update should use the updated CLSI MIC cutoffs to determine reporting to public health, independent of the susceptibility interpretation (e. g., an isolate with an MIC of 8 to meropenem [“intermediate” by pre-2010 CLSI interpretation, but “resistant” by CLSI guidelines starting in 2011] should still be reported to MDPH and submitted for further evaluation). Many, if not most, ertapenem mono-resistant Enterobacteriaceae do not actually rule-in as CRE.
2017%20MDPH%20CRE%20Toolkit_Ver%201%200.docx