The University of Osaka · Social Sciences
Professor Takashi Aoki's research lab specializes in aquatic animal health, with a focus on fish and amphibian pathogens, antimicrobial resistance, and bacterial virulence mechanisms. The lab investigates emerging infectious diseases in aquaculture, including herpesviruses like koi herpesvirus (KHV) and bacterial pathogens such as Edwardsiella tarda and Aeromonas liquefaciens. Key research directions include the molecular characterization of drug resistance genes, the role of outer membrane vesicles in bacterial pathogenesis, and the development of novel vaccines using bacterial components. The lab also contributes to understanding the genetic diversity and evolution of aquatic pathogens through comparative genomics and plasmid-mediated resistance studies.
Figures are computed from collected data and may differ slightly.
Since the mid-1990s, lethal infections of koi herpesvirus (KHV) have been spreading, threatening the worldwide production of common carp and koi (both Cyprinus carpio). The complete genome sequences of three KHV strains from Japan, the United States, and Israel revealed a 295-kbp genome containing a 22-kbp terminal direct repeat. The finding that 15 KHV genes have clear homologs in the distantly related channel catfish virus (ictalurid herpesvirus 1) confirms the proposed place of KHV in the fam
The florfenicol resistance gene (pp-flo) derived from a transferable R-plasmid of Pasteurella piscicida consisted of 1,122 nucleotides, and the predicted amino acid sequence showed 47.4% identity to that of a non-enzymatic chloramphenicol resistance gene (cmlA). The pp-flo gene was located in the downstream region of the sulfonamide resistance gene of the transferable R-plasmid.
SUMMARY: Thirty-nine out of 72 drug-resistant strains of Aeromonas liquefaciens isolated from cultured fish and soft-shelled turtles (Trionyx sinensis japonicus) in various districts of Japan carried transferable drug resistance factors. The fish included eel (Anguilla japonica), carp (Cyprinus carpio), ayu (Plecoglossus altivelis) and goldfish (Carassius auratus). The most common type of resistance factors had the markers of resistance to sulphanilamide and tetracycline and all belonged to the
Infection with Edwardsiella tarda, a gram-negative bacterium, causes high morbidity and mortality in both marine and freshwater fish. Outer membrane vesicles (OMVs) released from gram-negative bacteria are known to play important roles in bacterial pathogenesis and host immune responses, but no such roles for E. tarda OMVs have yet been described. In the present study, we investigated the proteomic composition of OMVs and the immunostimulatory effect of OMVs in a natural host, as well as the eff
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