Phenotypic Detection and Differentiation of Carbapenemase Classes Including OXA-48-Like Enzymes in Enterobacterales and Pseudomonas aeruginosa by a Highly Specialized Micronaut-S Microdilution Assay

Abstract

The objective of this study was to evaluate the Micronaut-S carbapenemase detection microtiter plate assay for the detection of carbapenemases and Ambler class determination. The Micronaut-S carbapenemase detection microtiter plate was tested using a challenging collection of 154 carbapenemase-producing and 150 carbapenemase-negative clinical strains of Enterobacterales and Pseudomonas aeruginosa The Micronaut-S carbapenemase detection assay was able to detect 148/154 carbapenemase producers correctly, whereas 5/150 non-carbapenemase-producing isolates tested as false positive. This resulted in an overall sensitivity of 96% and a specificity of 97%. Regarding the detection of the carbapenemase class, the sensitivities and specificities were 93%/100%, 96%/100%, and 97%/99% for class A (n = 27), class B (n = 54), and class D (n = 73) carbapenemases, respectively. The Micronaut-S carbapenemase detection microtiter plate represents an easy-to-use and valuable tool for accurate and reliable detection of carbapenemases. In addition, it provides identification of the class of carbapenemase in most cases which can provide significant therapy guidance.

Keywords: KPC; Micronaut; OXA-48; carbapenemases; detection of resistance mechanism; metallo-β-lactamases; microdilution; multidrug resistance.