Generation and selection of antibodies for a novel immunochromatographic lateral flow test to rapidly identify OXA-23-like-mediated carbapenem resistance in Acinetobacter baumannii

Introduction. The spread of carbapenem-resistant Acinetobacter baumannii has led to a worldwide healthcare problem. Carbapenem resistance in A. baumannii is mainly mediated by the acquisition of the carbapenem-hydrolyzing oxacillinase OXA-23. The phenotypic detection of carbapenem-producing A. baumannii is challenging and time-consuming. Hence, there is an unmet medical need for reliable and rapid diagnostic tools to detect OXA-23-producing Acinetobacter isolates to enable successful patient management. Aim. Development of an immunochromatographic lateral flow test (ICT) for the rapid and reliable detection of OXA-23-producing carbapenem-resistant Acinetobacter isolates. Methodology. For the development of an antibody-based ICT, we generated anti-OXA-23 monoclonal antibodies (MoAbs) and screened them sequentially for their ability to bind native OXA-23. Selected OXA-23-specific MoAbs were tested in different combinations for their capacity to capture and detect OXA-23His6 by sandwich enzyme-linked immunosorbent assay (ELISA) and ICT. A well-characterized collection of carbapenem-resistant Acinetobacter isolates with defined carbapenem resistance mechanisms were used to evaluate the specificity of the final OXA-23 ICT prototype. Results. The antibody pairs best suited for the sandwich ELISA format did not match the best pairs in the ICT format selected during the development process of the final prototype OXA-23 ICT. This prototype was able to differentiate between OXA-23 subfamily-mediated carbapenem resistance and carbapenem-resistant Acinetobacter isolates overexpressing other OXAs with 100  % specificity and a turnaround time of 20 min from culture plate to result. Conclusion. With this rapid detection assay one can save 12–48 h of diagnostic time, which could help avoid inappropriate use of carbapenems and enable earlier intervention to control the transmission of OXA-23-producing carbapenem-resistant Acinetobacter isolates to other patients and healthcare workers.