| Summary: | 碩士 === 東吳大學 === 微生物學系 === 93 === Vibrio vulnificus is an estuarine bacterium that causes serious wound infection and septicemia with high mortality. It is also transmitted through the consumption of raw contaminated seafood and caused the death. V. vulnificus is a global concerned foodborne pathogen and also becomes an important food poisoning pathogen in Taiwan. During food processing, pathogenic bacteria are challenged by various environmental stresses, such as heat, acid, low temperature, and dry treatments, and these bacteria will generate adaptive tolerance under sublethal stresses and thus enhances its risk in food hygiene.
In this study, physiological aspects of V. vulnificus under lethal or sublethal hypoosmotic stresses were analyzed. Sensitiveness of the environment and clinical bacterial strains to low salinity and protective effects of osmoprotectants were also examed. The cross-protection of adaptive hypoosmotic tolerance against other stresses, such as acid, heat, bile and food preservative treatment, were examined. Bacteria adapted to acid, heat or bile were also challenged by hypoosmotic stress.
Our data showed that decrease of the salt concentration increased the death of V. vulnificus and the clinical strains exhibited higher tolerance to the low salinity than those environmental strains. Osmoprotectants, such as glycine betaine or sucrose, showed obvious protection to V. vulnificus under low salinity, and also showed obvious recovery of the V. vulnificus injured under low salinity. Adaptive hypoosmotic tolerance protected V. vulnificus against low salinity but not against the high temperature and acid treatments. V. vulnificus adapted to non-lethal heat or acid treatment was not protected against low salinity, whereas cells adapted to bile treatment significantly cross-protected against low salinity. These results confirmed the adaptive hypoosmotic tolerance in V. vulnificus and partially clarify the cross-protective effects of different environmental stresses. These phenomena are important in the process of seafood.
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