Comparative analysis of sturgeon- and catfish-derived Yersinia ruckeri reveals the genetic variation and the risk of heavy antibiotic resistance

Sturgeon (Acipenseriformes) and catfish (Siluriformes) are two of the most famous special economic animals, accounting for 1.3 million tons of production in China. Enteric redmouth disease caused by Yersinia ruckeri is common in these two fishes. This study carried out a surveillance of ERM from April 2016 to August 2018 in the Sichuan province. The genotyping and the distribution of antibiotic resistance profiles (ARPs) and genes (ARGs) of Y. ruckeri were established in this study. The results showed that Y. ruckeri was a common pathogen in catfish and sturgeon, accounting for 25.56 % and 17.65 %, respectively. Sixteen strains were obtained and were clustered into 5 genotypes which has a fish-specific characteristic. Y. ruckeri had appeared resistance to 14 of the 20 antibiotics, and 39 antibiotic resistance genes were detected positively from 95 specific primers. Also, there were significant differences in antibiotic resistance profiles among different strains. The sturgeon-derived Y. ruckeri had higher detection rates of aac(6)-Ib(aka aacA4)-1, aac(6)-Ib(aka aacA4)-2, aac(6)-Ib(aka aacA4)-3, fox5 and acrF, and higher resistance rates to ampicillin, ciprofloxacin, levofloxacin, kanamycin, and neomycin compared with the catfish-derived strains. Our results indicated that Y. ruckeri might become an important pathogen in catfish and sturgeon culture in Sichuan, and there were different subspecies of variation. Besides, Y. ruckeri has enriched many antibiotic resistances that may help evolve into super bacteria.