Pseudomonas aeruginosa in Chinese mitten crab Eriocheir sinensis: Identification, pathogenic potential and control with Bdellovibrio powder.

Pseudomonas aeruginosa is a significant opportunistic pathogen affecting both humans and aquaculture animals. However, there has been no documented evidence linking P. aeruginosa to hepatopancreatic necrosis disease in Chinese mitten crabs Eriocheir sinensis. In the present study, P. aeruginosa isolate HX-1 was identified as a causative agent of hepatopancreatic necrosis disease in E. sinensis, and its pathogenic characteristics in terms of pathogenicity-related genes, antimicrobial resistance profiles, and virulence was comprehensively analyzed. Additionally, the in vitro and in vivo efficacies of Bdellovibrio powder against this isolate were evaluated. Genomic analysis revealed that isolate HX-1 consisted of a single circular chromosome, which harbored 236 virulence genes involved in bacterial adherence, biofilm formation, nutrition and metabolism, exoenzyme and exotoxin production, and immune modulation, as well as 63 resistance genes conferring resistances to cephamycin, disinfecting agents and antiseptics, sulfonamide, fluoroquinolone, macrolide, monobactam, aminoglycoside, phenicol, diaminopyrimidine, and other antimicrobials. Antimicrobial susceptibility testing and virulence assays confirmed multiple resistances of this isolate to aminoglycosides, cephems, carbapenems, fluoroquinolones, and penicillins, and determined its seven-day median lethal dose (LD50) of 2.69 × 105 CFU/mL in E. sinensis. Furthermore, the Bdellovibrio powder displayed an inhibitory effect against this isolate with a bacteriostasis rate ranging from 85.09% to 99.90% at concentrations of 0.2 to 1.0 mg/L, and resulted in relative percentage survivals of 66.67% to 83.33% at 5 to 15 mg/kg diet against its infection. To our knowledge, this is the first report of P. aeruginosa as a causative agent of hepatopancreatic necrosis disease in E. sinensis. These findings underscore the potential public health and aquaculture risks posed by P. aeruginosa, and suggest the use of Bdellovibrio powder as a promising biocontrol strategy for preventing P. aeruginosa infections in aquaculture.