One Health approach applied to the following up of antimicrobial resistance dissemination in freshwater fishfarms at the watershed level
Résumé
A research project (Resist3A) aimed to investigate the AMR dissemination upstream and downstream of two trout fish farms, located respectively at the source (FF1) and at the mouth (FF2) of a river impacted by agricultural, terrestrial farming and wastewater treatment plant. During 17 months, every two weeks, water samples were collected upstream and downstream two fish farms and biofilm samples were collected in a same fishpond per farm. Abiotic environmental parameters (pH, conductivity…) were measured too. Enumeration of E. coli, Aeromonas spp. and Pseudomonas aeruginosa was performed using culture methods on the 144 water samples and 72 biofilm samples collected. Antimicrobial susceptibility testing of a selection of E. coli (n=142), Aeromonas (n=355), and Pseudomonas aeruginosa (n=123) isolates was performed using agar diffusion method. The proportion of E. coli isolates, which were susceptible to all tested antimicrobials, was higher in water than in biofilm (92.7% vs 89%). None isolate was resistant to carbapenems or extended-spectrum betalactams. No multidrug resistant isolate was detected. Only 13 isolates were resistant to one or two classes of antibiotic. The Aeromonas isolates collected were collected from water samples (n=172) and from biofilm (n=183). From the source to the mouth in water sample, no decrease of susceptibility was observed for oxolinic acid, florfenicol, oxytetracycline, ceftazidime and meropenem. At the opposite, a slight reduction of susceptibility was observed for enrofloxacin. Isolates collected in the biofilm of the FF1, showed a reduced susceptibility to oxytetracycline and oxolinic acid. No reduction of susceptibility was observed among isolates collected in the biofilm of the FF2. On the contrary, of the results observed for E. coli, the proportion of Pseudomonas aeruginosa susceptible to all the 13 antibiotics tested was higher in biofilm than in water (100% vs 74.5%). These results confirm the importance of an approach including several compartments of the environment (water, biofilm), and three bacteria models allowed us to have a broader view of the AMR dissemination.