Abstract
PURPOSE: This study aimed to evaluate the performance of the RESIST-4 O.K.N.V immunochromatographic lateral flow assay for the detection of OXA-48, KPC, NDM and VIM carbapenemases in 100 clinical Enterobacteriaceae isolates using solid culture media. METHODOLOGY: In total, 100 clinical Enterobacteriaceae isolates with characterized β-lactamase enzymes (OXA-48 n=46, KPC n =4, NDM n =43 and VIM n =10) were evaluated using the RESIST-4 O.K.N.V assay. The assay was also evaluated using carbapenem-sensitive control strains and confirmed non-carbapenemase-producing Enterobacteriaceae clinical isolates resistant to carbapenems. Inter-rater agreement of the test was evaluated by four different users who tested 11 randomly selected isolates daily over 3 days. RESULTS: Overall accuracy of the assay was 99.5 %. For the detection of KPC, OXA-48 and its variants and VIM the assay correctly identified 100 % of the isolates when compared to PCR. Initial performance for NDM detection was sensitivity=95.3 %, specificity=100 %. Two PCR positive Providencia rettgeri isolates rendered false negative results on the assay. Retesting from a carbapenem zone of inhibition rendered a positive result for both isolates increasing the sensitivity to 100 %. No false positive results or cross reactions were detected. CONCLUSION: The RESIST-4 O.K.N.V is reliable, sensitive and specific for the detection of OXA-48, KPC, NDM and VIM carbapenemases. Further evaluation on improving NDM detection in organisms from the Proteeae tribe is warranted to determine optimal test conditions.