Performance of carbapenemase screening algorithms for detection of OXA-244-producing Escherichia coli

OXA-244-producing Escherichia coli emerge in Europe and are difficult to detect. We evaluated the performance of different carbapenemase-producing Enterobacterale (CPE) screening and confirmation protocols used across five clinical microbiology laboratories in the Netherlands for the detection of OXA-244-producing E. coli isolates.

Twelve E. coli isolates (CPE n = 9, non-CPE-ESBL n = 3) containing bla _OXA-244 (n = 5), bla _OXA-48(n = 1), bla _OXA-181 (n = 1), bla _KPC-2 (n = 1) and bla _NDM-5 (n = 1) were distributed to five laboratories. Laboratories performed identification, susceptibility tests and subsequent additional tests for resistance mechanisms in accordance with their local CPE screening and confirmation protocol which all adhered to the current Dutch guideline for CPE detection.

All laboratories correctly detected no carbapenemase in three E. coli isolates without carbapenemase genes and correctly determined the E. coli isolates with bla _KPC-2 and bla _NDM-5 as CPE. Detection rates of carbapenemase among the five E. coli isolates with bla _OXA-244 ranged from 0/5 (0%) to 4/5 (80%) isolates. One E. coli isolate with bla _OXA-244, a meropenem MIC ≤0.125 mg/L and an imipenem MIC ≤0.25 mg/L was not detected by any laboratory.

Differences in CPE screening and confirmation protocols across five laboratories contributed to inconsistent detection of OXA-244-producing E. coli. Laboratories that used a gradient strip test confirmed meropenem minimum inhibitory concentration (MIC) >0.25 mg/L CPE screening breakpoint detected fewer or no OXA-244-producing E. coli strains than laboratories that implemented additional measures in their CPE screening protocols. A key recommendation is that laboratories evaluate whether the performance of their CPE screening protocol remains adequate, considering the current epidemiology of emerging difficult-to-detect OXA-244-producing E. coli.