A novel air-dried multiplex high resolution melt assay for the detection of extended spectrum beta-lactamase and carbapenemase genes

Here we describe the development and evaluation of a novel an air-dried high-resolution melt (HRM) assay to detect eight major extended spectrum beta-Lactamase (ESBL) (SHV and CTXM groups 1 and 9) and Carbapenemase (NDM, IMP, KPC, VIM and OXA-48) genes that cause antimicrobial resistance. The assay was evaluated using 440 DNA samples extracted from bacterial isolates from Nepal, Malawi and UK and 390 clinical Enterobacteriaceae isolates with known resistance phenotypes from Nepal. The sensitivity and specificity for detecting the ESBL and Carbapenemase genes in comparison to the reference gel-base PCR and sequencing was 94.7% (95%CI: 92.5%-96.5%) and 99.2% (95%CI: 98.8%-99.5%) and 98.5% (95%CI: 97.0%-99.4%) and 98.5% (95%CI: 98.0%-98.9%) when compared to the original wet format. The overall phenotypic agreement was 91.1% (95%CI: 90.0%-92.9%) on predicting resistance to cefotaxime and carbapenems. We observed good inter-machine reproducibility of the air-dried HRM assay using the Rotor-Gene Q, QuantStudio™ 5, CFX96, LightCycler® 480 and MIC. Assay stability upon storage in the fridge (6.2°C ± 0.9), room temperature (20.35°C ± 0.7) and oven (29.7°C ± 1.4) were assessed at six time points for eight months and no loss of sensitivity occurred under all conditions. We present here a ready-to-use air-dried HRM-PCR assay that offers an easy, thermostable, fast and accurate tool for the detection of ESBL and Carbapenamase genes to improve AMR diagnosis and treatment. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The study was funded through the MRC Proximity to Discovery (P2D) award number MC\_PC\_17196. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: University of Malawi College of Medicine Research and Ethics Committee (COMREC), Blantyre, under study number P.08/14/1614 All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data is available on request from the corresponding author