Prevalence of integrons in Aeromonas isolates from fish

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Baron, Sandrine | Larvor, Emeline | Jouy, Eric | Le Bouquin-Leneveu, Sophie | Kempf, Isabelle | Chauvin, Claire | Morin, Thierry | Thuillier, Benoit | Le Piouffle, Anthony | Calvez, Ségolène | Feucherolles, Maureen | Wilhelm, Amandine | Gassilloud, Benoît

Edité par CCSD ; World Aquaculture Society -

National audience. Antimicrobial resistance (AMR) is increasing worldwide in humans, animals and the environment. Integrons are genetic elements involved in the dissemination of AMR, mostly among Gram-negative bacteria. Integrons are able to capture and express antibiotic resistance genes embedded within mobile gene cassettes Prevalence of integrons is well documented in Enterobacteriaceae, but data are still relatively rare in Aeromonas. Due to its ecological and genetic capabilities, Aeromonas is now proposed as an indicator of AMR dissemination in aquatic environment, and is considered, as well as integrons, as a vehicle of dissemination of antibiotic resistance genes. The aim of this study was to evaluate the prevalence of integrons in Aeromonas isolates from fishes: wild freshwater fishes, trout (fish farming) and diseased fishes (fish farming). A total of 310 Aeromonas were collected in France from wild freshwater fishes (n=109, in 2014), diseased fishes (n=124, 1985-2014), and from healthy trout coming from fish farming (n= 77, in 2014/2015). Class 1, class 2 and class 3 integrons were detected by a multiplex qPCR. Antimicrobial susceptibility of the isolates was assessed using the broth microdilution method. Eighty-one isolates harbored integrons. No integron was detected in isolates from wild freshwater fishes. Integrons were present in 54.8 % of the isolates recovered from diseased fishes and in 16.9 % of those recovered from healthy trout. Class 1 integrons were the most often detected (n=80), only one isolate recovered from trout harbored a class 2 integron. No class 3 integron was detected. In this study, we observed the highest prevalence of integrons in Aeromonas from diseased fishes and a higher prevalence in trout (fish farming) compared to isolates from wild freshwater fishes. It is assumed that this trend could be linked to the antibiotic selection pressure in fish farms, but further evaluation is necessary to investigate this point. The susceptibility profiles of the isolates and the link with integrons are under characterization.

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