TRANSFER AND PERSISTENCE OF MULTI-DRUG RESISTANCE PLASMIDS IN THE INTESTINAL MICROBIOTA OF CATFISH

<b>Project Methods</b><br> Our efforts will be to identify which bacteria species in the intestinal tract may receive MDR-plasmids after infection of catfish with donor strains. Other effort will be to determine the frequency of transfer and proliferation of the MDR-plasmids in commensal and pathogenic bacteria in the absence and presence of selection pressure. For the first objective, specific pathogen-free (SPF) catfish fingerlings will be stocked into tanks and inoculated with E. ictaluri strain MS-17-156 that carries MDR-plasmid by immersion. A non-treated control group will be included as a control group. The challenged fish will be euthanized at different time points post-infection and their intestines will be harvested for tissue culture assay. The frequency of transfer and proliferation of the MDR-plasmids in the catfish intestinal microbiome will be determined by a combination of culture-dependent methods and DNA sequencing. Quantitative PCR (qPCR) assays will be used to detect and quantify the presence of MDR-plasmids in the total DNA extracted from catfish microbiota. The prevalence and levels of MDR-plasmids will be analyzed by mixed model poisson regression. For the second objective, a similar setup will be conducted but with florfenicol and tetracycline treatment groups. Using this approach, the team will determine the impact of antimicrobial use on the transfer of MDR-plasmids.