Evaluation of temocillin and meropenem MICs as diagnostic markers for OXA-48-like carbapenemases

Sir, OXA-48-like carbapenemases are rapidly spreading in Europe and constitute the most common carbapenemase family identified amongst Enterobacterales referred to PHE’s Antimicrobial Resistance and Healthcare Associated Infections (AMRHAI) Reference Unit.1–3 Phenotypic detection of OXA-48-like carbapenemases can be challenging owing to both the low levels of carbapenem resistance and the cephalosporin susceptibility of strains that lack other β-lactam resistance mechanisms; there is also currently no reliable commercially available inhibitor for OXA-48-like carbapenemases to aid their detection. High-level temocillin resistance (MIC ≥128 mg/L) has been proposed as a diagnostic marker for OXA-48-like carbapenemases if used as part of an algorithm for carbapenemase detection.4 Following detection of reduced susceptibility to meropenem (MIC >0.12 mg/L), high-level temocillin resistance (MIC >128 mg/L) in the absence of synergy in combination disc testing is proposed...