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Seasonal variability of intestinal microbiota in rainbow trout (Oncorhynchus mykiss), with a particular attention to Aeromonas spp. as candidate indicator of antimicrobial resistance

Abstract : The objectives of this work were (1) to study the importance of Aeromonas bacterial genus in gut microbiota of farmed trout in relation with seasonal variability and (2) to evaluate the relevance of Aeromonas as bacterial indicator for antimicrobial resistance emergence in freshwater fish farming. The quantitative and qualitative bacteriological composition of trout gut microbiota was examined over a one-year period with regular sampling of five fish in a freshwater farm in Brittany, France. The composition of culturable flora was assessed by counts on selective and non-selective media. Gram-negative bacteria, in particular Aeromonas spp. isolates, were identified by cultural, biochemical and PCR analysis methods. Important variations were observed throughout the year, in both the quantitative (<10 2 cfu g -1 in cold season to 10 5 -10 6 cfu g -1 of gut tissues in warm season) and the qualitative composition of total heterotrophic aerobic microbiota. These variations were attributed to evolution of water temperature according to the seasonal cycle at this site. Antimicrobial susceptibility of Aeromonas spp. was tested against oxolinic acid, flumequine, enrofloxacin, oxytetracycline, chloramphenicol, florfenicol, ampicillin, gentamicine and streptomycin. Important variations of antimicrobial susceptibility patterns were observed: some strains presented a wild-type antimicrobial susceptibility pattern similar to strains present in unpolluted freshwater, but most presented acquired resistance to one or several antimicrobials. Moreover one strain was resistant to streptomycin, oxytetracycine, chloramphenicol and florfenicol. In conclusion, Aeromonas spp. are easy to isolate, and naturally susceptible to the main antimicrobial drugs used in aquaculture. However, their irregular detection over the year in rainbow trout gut limits their suitability as indicator for antimicrobial resistance.
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https://hal.inrae.fr/hal-02655960
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Submitted on : Friday, May 29, 2020 - 11:02:54 PM
Last modification on : Tuesday, June 15, 2021 - 3:31:17 AM

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  • HAL Id : hal-02655960, version 1
  • PRODINRA : 147363

Citation

Magali Naviner, Etienne Giraud, Hervé Le Bris, Françoise Armand, Catherine Mangion, et al.. Seasonal variability of intestinal microbiota in rainbow trout (Oncorhynchus mykiss), with a particular attention to Aeromonas spp. as candidate indicator of antimicrobial resistance. Revue de Médecine Vétérinaire, Ecole Nationale Vétérinaire de Toulouse, 2006, 157 (12), pp.599-604. ⟨hal-02655960⟩

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