Virulence, antimicrobial resistance characteristics, and intestinal microbial composition changes of Vibrio isolated from a Macrobrachium rosenbergii aquaculture system

During the breeding period of Macrobrachium rosenbergii, disease caused by Vibrio can cause cross water transmission because of their transfer between different breeding ponds at different breeding stages. Therefore, this study aimed to evaluate the antibiotic resistance risk, virulence, and population distribution four major pathogenic Vibrio species in the M. rosenbergii aquaculture system, and to explore the impact of Vibrio challenge on the intestinal health of M. rosenbergii. We isolated 391 bacterial strains from prawns, aquaculture water, and biological bait samples, 296 of which were identified as Vibrio using 16S rDNA sequencing. The main species included Vibrio parahaemolyticus, V. alginolyticus, V. harveyi, and V. cholerae. We detected six virulence genes among the four species. In the four species, the multiple antibiotic resistance (MAR) index ranged from 0.13 to 0.69, and 23.2% of the strains had MAR lower than 0.2. However, the antibiotic resistance pattern abundance index ranged from 0.16 to 0.29, showing homogeneity of Vibrio antibiotic phenotypes. The resistance quotient analysis showed that the dominant Vibrio had low or no resistance selection pressure under doxycycline, enrofloxacin, tetracycline, and ciprofloxacin. We detected only six resistance genes, and some resistance genotypes did not match the phenotypes. Upon Vibrio infection, the intestinal microbial community structure of M. rosenbergii changed, the intestinal barrier function was damaged, and the intestinal tissue showed structural damage. These findings provide data support for tracking infectious diseases in aquatic systems in China.