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Recent events linked to the Covid19 pandemic show us that it is no longer possible to reason human health without integrating that of animals, and that of all ecosystems, since they are closely interconnected. according to the One Health concept. Resistance to antibiotics acquired by the bacterial world is a major public health issue. The use of antibiotics for animal health and in human medicine can generate resistance to antibiotics in bacteria in the animal's microbiota. These resistances are likely to be transferred to humans through food. SECALIM researchers follow microbial dynamics from breeding to food. It is in this context that scientists from UMR BIOEPAR and SECALIM have joined their skills in animal health and food microbiology, to establish the antibiotic resistance profiles of bacteria of the genus Pseudomonas, one of the dominant genera of the core -microbiota of fresh fillets, filleted in the factory or under sterile laboratory conditions, of rainbow trout from two breeding sites (see previous study). The fifty-one bacterial isolates identified by qPCR and by MALDI-TOF mass spectrometry mainly belonged to the Pseudomonas fluorescens group. Their resistance was evaluated against ten antibiotics. Of the 51 isolates, fairly retained between the two breeding sites, 21 were considered resistant, in particular to ceftazidime and colistin, antibiotics used in human medicine. Seven isolates have been shown to be highly resistant to antibiotics used in aquaculture (oxytetracycline, florfenicol and sulfonamides) and as a last resort in human medicine (colistin). Resistance in Pseudomonas was predominantly associated with a single antibiotic (47.5%), more rarely with two antibiotics (17.6%) and only 2.0% of the isolates presented triple resistance. Multiple correspondence analysis did not show any correlation between the antibiotic resistance profile, the breeding site or the processing site.

In the light of this study, the number of multi-resistant isolates of Pseudomonas from the fluorescens group observed is low and the resistance profiles appear unrelated to the origin of these fresh fillets (breeding site and processing site). A better understanding of the role of these bacteria in the dissemination of antimicrobial resistance, between rainbow trout and humans, will require the characterization of the genetic elements of Pseudomonas populations, using whole genome sequencing approaches.
Associated publication: Oberle, K., Bouju-Albert, A., Helsens, N., Pangga, G., Prevost, H., Magras, C., Calvez, S. 2021. No evidence for a relationship between farm or transformation process locations and antibiotic resistance patterns of Pseudomonas population associated with rainbow trout (Oncorhynchus mykiss). Journal of Applied Microbiology. doi: 10.1111/jam.15344

Funding and partners: this study was performed by INRAE-Oniris SECALIM and BIOEPAR research units in the framework of the FOOD RESISTOME project, with the financial support of RFI Food For Tomorrow (Région des Pays de la Loire).