Evaluation of the Carba NP test for carbapenemase detection in Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp., and its practical use in the routine work of a national reference laboratory for susceptibility testing.

The aim of this study was to evaluate the Carba NP test (and CarbAcineto) for the detection of carbapenemases in Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp., and to assess its usefulness in the routine work of the National Reference Centre for Susceptibility Testing (NRCST) in Poland. The evaluation of the Carba NP/CarbAcineto tests was carried out on a group of 81 Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp. isolates producing KPC-, NDM-, VIM-, IMP- or OXA-48, -23, -24/40, -58-type carbapenemases, and on 26 carbapenemase-negative strains cultivated on a broad panel of microbiological media. Subsequently, the performance of the Carba NP/CarbAcineto tests was assessed on 1282 isolates of Enterobacteriaceae, Pseudomonas spp. and Acinetobacter spp. from Polish hospitals, submitted to the NRCST during a 9-month period in 2014. The Carba NP/CarbAcineto results were compared with other phenotypic tests and/or polymerase chain reaction (PCR). The impact of the media on the results of the Carba NP/CarbAcineto tests was observed, with the Columbia blood agar yielding the highest sensitivity and clarity of the results. Furthermore, the Carba NP/CarbAcineto tests were included in the NRCST routine procedure for carbapenemase identification. The sensitivity and specificity of the Carba NP test were 95.8% and 93.3%, respectively, for Enterobacteriaceae, and 97.5% and 99.0%, respectively, for Pseudomonas spp. The sensitivity of the CarbAcineto test for Acinetobacter spp. was 88.9%. This study confirmed the usefulness of the Carba NP/CarbAcineto tests for the rapid detection of various types of carbapenemases.