"Simplified carbapenem inactivation method (sCIM) as a reliable tool for detecting OXA-48-producing enterobacterales in clinical practice".

PURPOSE: Carbapenemase-producing Enterobacterales (CPE), particularly OXA-48-producing Enterobacterales, represent a major diagnostic and therapeutic challenge due to their frequent low-level carbapenem resistance and delayed microbiological detection. Rapid confirmation of carbapenemase production is essential to optimize antimicrobial therapy and infection control measures.

METHODS

This study evaluated the simplified carbapenem inactivation method (sCIM) for detection of OXA-48-producing Enterobacterales. Unlike the conventional mCIM, sCIM eliminates the preliminary carbapenem inactivation incubation step, simplifying the workflow and reducing turnaround time. A total of 150 OXA-48-producing Enterobacterales were analyzed, together with additional VIM-, KPC-producing, and non-carbapenemase-producing isolates collected from clinical specimens at the Hospital Central de la Defensa "Gómez-Ulla" in Spain. Carbapenemase production was confirmed using the Xpert® Carba-R molecular assay.

RESULTS

The sCIM detected all OXA-48-producing Enterobacterales with 100% sensitivity (95% CI: 97.6-100%) and no indeterminate results, including isolates with low ertapenem MICs. Results were available after 16-18 h of incubation without previous 4-hour carbapenem inactivation step, simplifying laboratory workflow compared with the conventional mCIM.

CONCLUSIONS

The rapid detection of OXA-48-producing Enterobacterales remains a major diagnostic challenge due to their frequently low carbapenem MICs and subtle phenotypic expression. This study demonstrates that sCIM provides a simple, reliable, and highly sensitive method for detecting these isolates, even in cases with borderline susceptibility profiles. Given its low cost and ease of implementation, sCIM represents a valuable tool for routine clinical laboratories, particularly in high-prevalence or resource-limited settings.