SalmoSim AMR

The development, progression, and dissemination of antibiotic resistance (AMR) are influenced by interlinked human, animal, and environmental ecosystems, posing severe risks to human health. Conjugative plasmid transfer drives the rapid dissemination of AMR among microbial populations. Mitigating antibiotic resistance spread requires an understanding of the dynamics of AMR transfer among microbial communities, as well as the role of various microbial taxa as potential reservoirs that promote long term AMR persistence. Here, we employed Hi-C, a high-throughput, culture-free technique, combined with qPCR, to monitor carriage and transfer of a multidrug-resistant plasmid within an Atlantic salmon in vitro gut model during florfenicol treatment, a benzenesulfonyl antibiotic widely deployed in fin-fish aquaculature. Microbial communities from the midgut (pyloric ceaca) of three healthy adult farmed salmon were inoculated into three bioreactors developed for the SalmoSim gut systen. The model system was inoculated with an Escherichia coli strain ATCC 25922 carrying plasmid pM07-1 and treated with treated with a florfenicol (XX conc) for five days prior to a washout / recovery phase. Hi-C and metagenomic sequencing identified numerous transfer events, including Gram-negative and Gram-positive taxa and, crucially, widespread transfer and persistence of the plasmid in the absence of florfenicol. Our findings highlight the role of commensal teleost gut flora as a reservoir for AMR, and our system provides a model to study how different treatment regimes and interventions may be deployed to mitigate against AMR persistence.