Conference in Seminarios VISAVET 2023

February 15^th, 2023

Navarro-Gonzalez N.

In Europe, Recirculating Aquaculture Systems (RAS) are increasingly established. These intensive fish farms where water is nearly fully recycled are deemed the farming system of the future. However, little is known about the occurrence of antimicrobial resistance (AMR) in this novel food-producing environment and on the efficacy of water treatment to reduce AMR.
Our aquaculture experimental facility is a very interesting model for the study of AMR in RAS: it uses city water exclusively, thus eliminating the most important vehicle of AMR. In this scenario, we are able to evaluate whether the other inputs to the system (fish and feed) can be sources of AMR-bacteria.
We performed a longitudinal observational study at our facility from February to July 2022. The facility was operating at full capacity to raise rainbow trout and we monitored monthly the presence of selected bacteria in all compartments: water, sediment, fish feces, feed, biofilm. Tracked bacteria included fecal bacteria (E. coli, Enterococcus) and aquatic bacteria (Aeromonas, Pseudomonas), all of which are also considered good indicators of AMR from the environment. Very interestingly, our longitudinal study design enabled us to observe what happened in environmental bacteria after a florfenicol treatment administered to rainbow trout to treat flavobacteriosis. In other instances we found Aeromonas resistant to antibiotics that are important for human health (cefotaxime, ciprofloxacin, and others). Another unexpected result was commercial feed being contaminated with Aeromonas and Enterococcus

	Ecole Nationale Vétérinaire, Agroalimentaire et de l´alimentation de Nantes (Oniris).
	Centre INRAE Val-de-Loire.
	Servicio de Zoonosis de Transmisión Alimentaria y Resistencia a Antimicrobianos (ZTA). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).