Genetic Characterization and Pathological Analysis of a Novel Bacterial Pathogen, Pseudomonas tructae, in Rainbow Trout (Oncorhynchus mykiss)

Pseudomonas species are one of the most prevalent bacterial species globally distributed in forest soil, river water, and human or animal skin. Some species are pathogens or opportunistic pathogens in hospitalized patients, animals, and plants. Various Pseudomonas species, including Pseudomonas putida, P. plecoglossicida, P. aeruginosa, and P. fluorescens, are known fish pathogens; P. fluorescens and P. putida cause severe losses in rainbow trout farming. Therefore, we investigated and isolated the pathogen that is responsible for mortality in a rainbow trout farm in Korea. The isolated bacterium was a strain of P. tructae, which was recently classified in the P. putida group. We performed taxonomical analysis of the bacteria in our previous study. In this study, we investigated the pathogenicity and clinical symptoms of P. tructae and analyzed its genomic characteristics. The pathogenicity of the strain was tested via challenge experiments in healthy rainbow trout and histopathologic analysis of the infected fish. Genome sequence was analyzed to identify the bacterial genes that are involved in antibiotic resistance and virulence. This is the first study reporting P. tructae as an emerging pathogen that is responsible for mortality in rainbow trout fisheries and providing the genome sequence of P. tructae.