Comparative genome analyses of three serotypes of Lactococcus bacteria isolated from diseased cultured striped jack (Pseudocaranx dentex).

Lactococcosis, caused by members of the genus Lactococcus, represents a devastating disease inducing mass mortalities and economic losses in many fish species worldwide. The present work aimed to compare the whole genome sequences of three different serotypes of Lactococcus garvieae isolated from diseased cultured striped jack (Pseudocaranx dentex) in Ehime prefecture, Japan. The three serotypes showed different virulence in the challenge test using Japanese amberjack (Seriola quinqueradiata). The genome sequencing revealed that two of the strains (serotype I and serotype III) were identified as L. garvieae, while the third strain (serotype II) was identified as L. formosensis. The chromosome sizes of the three serotypes ranged from 1.9 to 2.0 Mb; the GC content ranges were 38.2 to 38.9%; and the numbers of predicted protein-coding sequences (CDSs) were from 1922 to 1959. Only the serotype II harbours two plasmids, sizes of around 14 kb and 9 kb. The detected virulence factors varied among the different serotypes with some shared factors like adherence, anti-phagocytosis, secretion system, toxin (haemolysin), serum resistance, antimicrobial resistance and others. The genomes also contained factors responsible for resistance to toxic compounds. The genome of the serotype III tended to encode more prophage regions than the other serotypes.

Pathological and immunohistochemical studies following the experimental infection of ayu (Plecoglossus altivelis) by Edwardsiella ictaluri.

In recent decades, several mass mortalities were recorded in riverine ayu (Plecoglossus altivelis) in Tokyo Metropolis, Hiroshima Prefecture, and Yamaguchi Prefecture, Japan; in these outbreaks, microbiological and pathological examinations revealed Edwardsiella ictaluri as the causative agent. In this study, histopathological findings and immunohistochemical localization of the bacteria following experimental infection of ayu were discussed. Infection experiments were performed using 44 healthy cultured ayu fingerlings using E. ictaluri isolate (H90). The fish were injected with the isolate intraperitoneally with a dose of 5.1 × 105 cfu/fish, while the control fish were injected with sterile phosphate buffered saline. The fish were observed for clinical signs, with daily collection of dead fish, and isolation of bacteria from the posterior kidney was performed and confirmed to be E. ictaluri by slide agglutination using anti-PH0744 serum. Daily collection of five moribund fish for necropsy and tissue specimens collection from hepatopancreas, spleen, posterior kidney, gills, brain, heart, and intestine for histopathological and immunohistochemical examination. Post-mortem lesions were recorded as exophthalmia, bloody ascitis, hemorrhagic kidney and distended gallbladder, meningio-encephalitis, hemorrhagic vent, and petechial hemorrhages on viscera. Histopathological examination revealed diffuse severe congestion in blood vessels and several degenerative and necrotic changes inconcurrent with positive antigenic staining by immunohistochemistry.

Trichosporon jirovecii infection of red swamp crayfish (Procambarus clarkii).

One hundred and twenty-nine isolates of Trichosporon jirovecii were isolated from the melanized exoskeleton as well as eyestalks, gills, muscle and haemolymph of red swamp crayfish (Procambarus clarkii) collected from the River Nile, during summer 2015. Isolates were similar morphologically, biochemically and genetically. Also, random amplified polymorphic DNA (RAPD) analysis exhibited no polymorphism among the tested isolates. Virulence factors such as chitinase, protease, lipase activities and biofilm formation were examined. Challenge test, using a representative isolate (Tj_ASU8), proved its pathogenicity against crayfish. Magnesium oxide nanoparticles had a good antifungal activity with a minimum fungicidal concentration of 8 mg/ml. To the best of our knowledge, this is the first report for isolation of T. jirovecii from red swamp crayfish, showing melanization, from the River Nile. We assume that infected crayfish may act as a vector for this fungus and can disseminate infection to all susceptible hosts in the vicinity.

Complete Genome Sequence of the Edwardsiella ictaluri-Specific Bacteriophage PEi21, Isolated from River Water in Japan.

We present the complete genome sequence for a novel Edwardsiella ictaluri-specific bacteriophage, PEi21, isolated from river water in Japan. An initial comparative genome analysis revealed that the phage was closely related to the previously reported Edwardsiella tarda phage MSW-3 isolated from a red sea bream farm in Japan.

Intracellular replication of Edwardsiella tarda in murine macrophage is dependent on the type III secretion system and induces an up-regulation of anti-apoptotic NF-kappaB target genes protecting the macrophage from staurosporine-induced apoptosis.

Edwardsiella tarda is a pathogen with a broad host range that infects both animals and humans. Resistance to phagocytic killing may be involved in the pathogenicity of this bacterium. Here we show that intracellular replication of E. tarda in murine macrophages is dependent on the type III secretion system and induces an anti-apoptotic effect by up-regulating anti-apoptotic NF-kappaB target genes. The wild-type strain replicates within the phagosomal membrane of macrophages; whereas the type III mutant does not. Microarray analysis shows the mRNA expression level of NF-kappaB target genes (e.g. pro-inflammatory cytokines and anti-apoptotic genes) in macrophages infected with the wild-type strain were up-regulated compared to macrophages infected with the type III mutant. Up-regulation of Bcl2a1a, Bcl2a1b, cIAP-2, and TRAF1 genes induced expression of anti-apoptotic proteins to protect macrophages from apoptosis induced by staurosporine. Further, this protection was inhibited by adding kamebakaurin, an inhibitor of NF-kappaB activation and was confirmed using an NF-kappaB reporter gene assay. Up-regulation of anti-apoptotic NF-kappaB target genes is responsible for the anti-apoptotic activity of E. tarda and is required for intracellular replication in murine macrophages.