Evaluation of LAMP-based assays for carbapenemase genes

Purpose. Rapid and accurate detection of carbapenem resistance is a critical requirement for the selection of appropriate therapy and initiation of infection control measures. Although several tests are available, their use is limited by one or more factors. Phenotypic tests are lengthy, have variable sensitivity and specificity and do not generally identify the carbapenemase. Molecular assays overcome many of these issues but cost can be a barrier to adoption, particularly in low-resource settings. To address the need for affordable, molecular tools, we have assessed the performance characteristics of loop-mediated isothermal amplification (LAMP)-based assays for the major carbapenemase genes, bla_NDM, bla_KPC, bla_OXA-48, bla_OXA-23 bla_VIM and bla_IMP.Methodology. The assays were validated using 1849 Gram-negative Indian clinical isolates obtained from seven hospitals and diagnostic centres.Results. The assays had diagnostic sensitivities of 98.14 %, 98.92 %, 100 %, 98.48 %, and diagnostic specificities of 98.94 %, 99.61 %, 97.42 %, 99.38 % for bla_NDM, bla_OXA-48, bla_OXA-23 and bla_VIM, respectively. Due to a low number of isolates positive for bla_KPC and bla_IMP, the performance characteristics of assays for these two genes could not be suitably evaluated.Conclusion. The performance characteristics suggest suitability for diagnostic and surveillance purposes.