Pathogenicity potential of antimicrobial-resistant Photobacterium damselae subsp. damselae isolated from maricultured and wild-caught fish of the southeast coast of India

Antimicrobial resistance and zoonotic pathogen transmission from wild fish to high-density cage-cultured fish are two of the emerging concerns in mariculture. Photobacterium damselae is one of the most destructive bacterial pathogens which is responsible for huge economic loss to the cage culture systems. To investigate the above, both wild-caught and cage-cultured fish were collected from the southeast coast of India. P. damselae subsp. damselae was isolated and their genotypic profiling was done using a specific multiplex polymerase chain reaction. Out of 280 isolates, 61 isolates were confirmed as P. damselae subsp. damselae. The overall prevalence of P. damselae subsp. damselae in wild fish was significantly higher compared with cage-cultured fish. Among the wild fish, parrot fish showed more prevalence when compared with other fish. Around 90% of the identified bacterial isolates were multiple antibiotic-resistant and carried antibiotic resistance genes such as beta-lactam and streptomycin genes. To know the virulence of P. damselae bacteria isolated from wild-caught fish to commercially important cage-cultured fish (cobia and silver pompano) experimentally, a challenging study was carried out. The results revealed that cobia and silver pompano showed 100% and 85% mortality at a bacterial concentration of 3.5 x 10(4) CFU Fish(-1) and 2.75 x 10(6) CFU Fish(-1) respectively. Severe tissue damage and ulceration were also noticed in both fish. In conclusion, the present study found a high rate of AMR in P. damselae subsp. damselae isolated from the fish of the southeast coast of India that exhibit the strong pathogenic potential to cage-cultured fish.