For an E. coli isolate with an ESBL, the CLSI recommends that susceptibility reports for cephalosporins should be:

• A Reported as per actual MIC regardless of ESBL detection
• B Amended to resistant for all third-generation cephalosporins irrespective of MIC
• C Suppressed and only carbapenems reported
• D Reported using revised (lowered) breakpoints that inherently account for ESBL effect ✓

Explanation

Current CLSI (2010 onwards) and EUCAST guidelines revised breakpoints for cephalosporins against Enterobacterales downward, meaning susceptibility is now reported based on actual MIC against the new (lowered) breakpoints without requiring phenotypic ESBL confirmation to change the report. Isolates with high MICs exceeding these new breakpoints will be correctly categorised as resistant. The old practice of automatically calling all cephalosporins resistant for any ESBL producer has been replaced by this MIC/breakpoint-based approach.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

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