Comparison of three colloidal gold immunoassays and GeneXpert Carba-R for the detection of Klebsiella pneumoniae bla _KPC-2 variants

Abstract

The increasing use of ceftazidime-avibactam has led to the emergence of a wide range of ceftazidime-avibactam-resistant bla KPC-2 variants. Particularly, the conventional carbapenemase phenotypic assay exhibited a high false-negative rate for KPC-2 variants. In this study, three colloidal gold immunoassays, including the Gold Mountainriver CGI test, Dynamiker CGI test and NG-Test CARBA5, and GeneXpert Carba-R, were used to detect the presence of KPC-2 carbapenemase and its various variants in 42 Klebsiella pneumoniae strains. These strains covered bla KPC-2 (13/42) and 16 other bla KPC-2 variants including bla KPC-12 (1/42), bla KPC-23 (1/42), bla KPC-25 (1/42), bla KPC-33 (6/42), bla KPC-35 (1/42), bla KPC-44 (1/42), bla KPC-71 (1/42), bla KPC-76 (8/42), bla KPC-78 (1/42), bla KPC-79 (1/42), bla KPC-100 (1/42), bla KPC-127 (1/42), bla KPC-128 (1/42), bla KPC-144 (1/42), bla KPC-157 (2/42), and bla KPC-180 (1/42). For KPC-2 strains, all four assays showed 100% negative percentage agreement (NPA) and 100% positive percentage agreement (PPA) with sequencing results. For all 16 KPC-2 variants, GeneXpert Carba-R showed 100% NPA and 100% PPA, and the three colloidal gold immunoassays showed 100% NPA, while the PPAs of the Gold Mountainriver CGI test, Dynamiker CGI test, and NG-Test CARBA5 were 87.5%, 87.5%, and 68.8%, respectively. We also found a correlation between the mutation site in the amino acid of the variants and false-negative results by colloidal gold immunoassays. In conclusion, the GeneXpert Carba-R has been proven to be a reliable method in detecting KPC-2 and its variants, and the colloidal gold immunoassay tests offer a practical and cost-effective approach for their detection. For the sample with a negative result by a colloidal gold immunoassay test but not matching the drug-resistant phenotype, it is recommended to retest using another type of kit or the GeneXpert Carba-R assay, which can significantly improve the accuracy of detection.

Complete Genome Sequence of a Klebsiella pneumoniae Strain Carrying Novel Variant blaKPC-203, Cross-Resistant to Ceftazidime/Avibactam and Cefiderocol, but Susceptible to Carbapenems, Isolated in Italy, 2023

“…These variants are characterized by impaired carbapenemase activity and the restoration of carbapenem susceptibility. Moreover, while molecular testing is capable of detecting all KPC Ω-loop mutants, lateral flow immunoassays and main phenotypic carbapenamse detection methods fail to detect these variants with diminished carbapenemase activity [ 7 , 10 , 11 ].…”