Assessment of freshwater fish farms for the identification of the geographical areas harbouring antimicrobial resistance

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Assessment of antimicrobial resistance (AMR) in freshwater fish farms has been rarely investigated. Aeromonas are considered as an indicator organism for monitoring AMR in aquatic environment. Identification of the geographical areas harbouring AMR have implications for developing AMR mitigation strategies. The present study investigated the prevalence of AMR in freshwater fish farms (n = 124) in four districts (A-D) of Uttar Pradesh, India. The study revealed significantly higher AMR in fish farms of district D for ceftazidime, cefotaxime and trimethoprim-sulfamethoxazole. Similarly, AMR to ciprofloxacin and tetracycline was significantly higher in district A, and cefoxitin (FOX) in district B. District D also showed the highest number of MDR strains, AmpC and ESBL producers. Overall, maximum AMR was seen to β-lactams (35.5%) and aminoglycosides (14.5%). Twenty-five AMR phenotypes and eighteen AMR genotypes were detected in the study. The farms of district D showed significantly higher number of resistant phenotypes (≥3 antimicrobials). Furthermore, the study identified the species of Aeromonas contributing to AMR. Two clusters were observed: cluster I- resistant to FOX only, and cluster II (comprising of A. caviae and A. veronii bv veronii)- resistant to multiple antimicrobials and included majority of AmpC producers. A. caviae had significantly higher MAR than other Aeromonas species. The ARGs shared among the cluster II species and its close relative A. veronii bv sobria were blaTEM,sul1, tet(E) and blaCIT. Overall, our study identified the geographical districts harbouring higher AMR in the freshwater fish farms. These findings suggest the need for spatial assessment of AMR in aquaculture.