Evaluation of a Loop-Mediated Isothermal Amplification Assay to Detect Carbapenemases Directly From Bronchoalveolar Lavage Fluid Spiked With Acinetobacter spp.

A total of 22 Acinetobacter spp. strains producing OXA-23, OXA-40, OXA-58, NDM, and IMP were selected. Eazyplex SuperBug Complete A kit, used with the Genie II device, is a molecular diagnostics kit that detects a selection of genes that express carbapenemases (bla_KPC, bla_NDM, bla_VIM, bla_OXA–48, bla_OXA–23, bla_OXA–40, and bla_OXA–58).

Negative BAL samples were identified, McFarland solutions were prepared from each of the 22 Acinetobacter strains and serial dilutions in saline solution were made to finally spike BAL samples to a concentration of 10² and 10³ CFU/ml. Fifteen concentrations out of the 44 tested out did not provide detection of the carbapenemase-producing gene, all but one being at the lowest concentration tested at 10² CFU/ml; therefore, the limit of sensitivity is 10³ CFU/ml. This assay represents the kind of advantages that investing in molecular diagnostics brings to the clinical practice, allowing the identification of carbapenemases in less than 30 min with a sensitivity of 10³ CFU/ml.