Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2014

Aeromonas hydrophila is a Gram negative facultative anaerobe found in fresh water environments, including ground water, surface waters, and marine waters. A. hydrophila is the most common water fish pathogen infecting fish, amphibians, reptiles and humans and can cause diseases such as hemorrhagic septicemia, dropsy, ulceration, asymptomatic septicemia and exophthalmos. A. hydrophila secreted many extracellular proteins (ECPs) which contribute significantly to their effective infection, wide distribution, and great adaptability to environmental changes. The bacterial strain used in this study has high pathogenicity and also its ECPs have high pathogenicity. In this study we were focusing on skin necrosis by ECPs in gold fish. When gold fishes were injected subcutaneously with ECPs, their skin appears necrosis. To gain insights into ECPs which can cause skin necrosis in media, we conducted the proteomics approach. We conducted diverse protein precipitation and purification method such as ammonium sulfate precipitation, gel filtration chromatography, anion exchange chromatography. As a result, proteins in specific fraction obtained through a gel filtration chromatography caused skin necrosis in gold fish. We also confirmed that ECPs are important protective antigens that induce immune responses to resist A. hydrophila infection by challenge test. In further studies, the protein in specific fraction will conduct analysis of MALDI-TOF assay. And the analysis results for a particular protein will be used to make a subunit vaccine by overexpression vector. We will expect that the subunit vaccine could have high immunogenicity and protect the host against to the A. hydrophila infection.