Carbapenemase investigation with rapid phenotypic test (RESIST-4 O.K.N.V) and comparison with PCR in carbapenem-resistant Enterobacterales strains

RESİST-4 O.K.N.V. assay is a lateral immunochromatocraphic test for the identification of oxacillinase (OXA)-48-like, Klebsiella pneumoniae carbapenemase (KPC), New Delhi metallo-β-lactamase (NDM), and Verona integron-encoded metallo-β-lactamase (VIM) producing strains. It was aimed to evaluate the performance of the RESIST-4 O.K.N.V. test and to compare it with the reference method polymerase chain reaction (PCR). Also, the objective was to determine the distribution of carbapenemase types of CRE strains isolated in our hospital.

Between January 2016-October 2019, 187 strains isolated from clinical samples were included in this study. Bacterial identification was done using MALDI-TOF MS. Antibiotic susceptibility tests were studied with the VITEK-2 automated system. Meropenem minimum inhibitory concentrations (MICs) were determined by the gradient test. All strains were studied with the RESIST-4 O.K.N.V. test and then the strains were selected for the PCR test. blaOXA-48, blaNDM, blaKPC, and blaVIM were investigated with PCR. K. pneumoniae NCTC® 13438 (KWIKSTIKTM, Microbiologics®,USA) was used as the positive control, E. coli ATTC® 25922 TM (Microbiologics®,USA) and three carbapenem-sensitive clinical isolates were also used as the negative control.

Meropenem MIC50 and MIC90 values were determined to be >32 mg/L. With PCR blaOXA-48, blaNDM, blaKPC, and blaVIM were detected in 79, 63, 20, and 4 strains, respectively. blaOXA-48 and blaNDM were found together in 51 of the isolates. blaOXA-48, blaNDM, blaKPC, and blaVIM were not detected in two strains with carbapenem resistance in susceptibility tests. The sensitivity of the immunochromatographic test was 100% for OXA-48, KPC, and VIM but 84.1% for NDM. Specificity was determined as 100% for OXA-48, NDM, KPC, and VIM.

RESIST-4 O.K.N.V. test showed high sensitivity and specificity in detecting OXA-48, KPC, NDM, and VIM type carbapenemases. However, it should be kept in mind that there may be false-negative results related to NDM.