Repeatable immersion infection with Photobacterium damselae subsp. piscicida reproducing clinical signs and moderate mortality

Abstract

Pseudotuberculosis is a bacterial septicaemia caused by Photobacterium damselae subsp. piscicida in several marine fish species. Yellowtail Seriola quinqueradiata is the most sensitive fish species to this disease. The internal organs of naturally infected yellowtail exhibit whitish spots, tubercle-like tissue structures, consisting of bacterial accumulations. There have been many trials for experimental infection, however adequate method of infection that reproduces moderate mortality and primary clinical signs has not yet established. Present investigation evaluated an immersion infection method by using logarithmic culture-phase bacteria resulting in higher mortality than that using stationary culture-phase bacteria. Typical white spots on the spleen and kidney were also observed constantly in dead fish. Transmission electron microscopy and fluorescent antibody microscopy showed bacterial clusters not only in the spleen and kidney but also in the blood channels in the secondary gill filaments. These results were confirmed repeatedly by plural experiments. The use of logarithmic-phase bacteria in immersion infection is an appropriate technique to reproduce moderate mortality and primary clinical signs, which will be a reliable infection method also for the challenge test of pseudotuberculosis vaccine.

Influence of dietary administration of a probiotic strain Shewanella putrefaciens on senegalese sole (Solea senegalensis, Kaup 1858) growth, body composition and resistance to Photobacterium damselae subsp piscicida

“…The natural route of infection for P. damselae subsp. piscicida is unknown to date (Nagano, Inoue & Kawai 2009). In the present study, i.p.…”

Development of a real‐time PCR assay for rapid detection and quantification of Photobacterium damselae subsp. piscicida in fish tissues

“…All fish dead during the challenge showed high bacterial load in the three tissues analysed (i.e., spleen, liver and gills) with spleen consistently showing higher levels of bacterial colonization than gills and liver. Recently, the early process of Phdp infection was investigated in Seriola quinqueradiata by immersion challenge (Nagano, Inoue, Kawai, & Oshima, ). This study clearly indicated the gills as the site of election to initiate infection, while internal organs (spleen, kidney) appeared to be the final tissues where bacterial proliferation occurs.…”

Administration of probiotics affects Artemia franciscana metanauplii intestinal ultrastructure and offers resistance against a Photobacterium damselae ssp. piscicida induced oxidative stress response

“…The culture titre was determined in 100 μL of the bacterial suspension by preparing serial dilutions in tubes containing 900 μL of culture medium, transferring 100 μL and plating. An OD630 nm∼0.9 of the initial culture corresponded to approximately 10 9 bacteria cells/mL [61] . Artemia metanauplii that received no pathogen served as control and survival was monitored throughout the experiment (24–144 h).…”