Detection of OXA-23 and OXA-58 in Proteus mirabilis by immunochromatographic assays

Proteus mirabilis is increasingly recognized as a carrier of carbapenemases, which are particularly difficult to identify, since most isolates have low carbapenem MICs. Additionally, most phenotypic tests (e.g. CARBA NP, mCIM) have insufficient sensitivity in this species. Furthermore, OXA-23 and OXA-58 are frequent in carbapenemase-producing Proteus but not included in most molecular and immunochromatographic assays for carbapenemase detection in Enterobacterales. The RESIST ACINETO lateral flow test (CORIS BioConcept) was recently developed for the detection of OXA-23, OXA-58/OXA-40, and NDM in Acinetobacter spp. The aim of this study was to investigate whether a combination of the RESIST-5 O.K.N.V.I., developed for Enterobacterales, and the RESIST ACINETO could improve the detection of carbapenemases in P. mirabilis. Ninety carbapenemase-carrying P. mirabilis isolates were analyzed by whole genome sequencing. All isolates were evaluated by the recently published carbapenemase-detection algorithm for P. mirabilis, followed by RESIST-5 and RESIST ACINETO assay. The algorithm achieved a sensitivity of 97.8%. In comparison, sensitivity/specificity among targeted carbapenemases was 96.3%/97.2% for RESIST ACINETO and 96.4%/100% for RESIST-5. In combination, a sensitivity of 97.8% was achieved. The sensitivity was excellent for OXA-23 (23/23, 100%) and NDM (18/18, 100%), but lower for OXA-58 (12/13, 92.3%) and OXA-48-like (24/25, 96.0%). The RESIST ACINETO and RESIST-5 performed well in detecting carbapenemases in P. mirabilis, particularly for the emerging OXA-23-producing P. mirabilis. The assays have the potential to improve carbapenemase detection in the routine diagnostic laboratory for this challenging species.IMPORTANCEOXA-23 and OXA-58 are among the most frequent carbapenemases in Proteus mirabilis but are often missed because of the difficult detection. In this article, the performance of immunochromatographic assays for the rapid and easy detection of these enzymes is assessed. The study includes a very large set of molecularly well-characterized isolates. The present work demonstrates that the notoriously challenging detection of carbapenemases in P. mirabilis can be achieved by immunochromatographic assays, enabling laboratories outside of academic centers to reliably detect these emerging carbapenemases in a short time. This will help prevent the further spread of carbapenemase-producing P. mirabilis in hospitals.