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Bacteremia in suckling rabbits after oral challenge with Vibrio parahaemolyticus
Abstract:
Vibrio parahaemolyticus, a halophilic marine enteropathogen, produces diarrhea in man after ingestion of contaminated seafood. Only strains capable of producing beta-hemolysis (Kanagawa-positive strains) are enteropathogenic. Yet the majority of marine isolants are nonhemolytic and Kanagawa negative. Studies were initiated in suckling rabbits in an attempt to elucidate pathogenetic mechanisms. Fasting animals were infected orally with Kanagawa-positive and Kanagawa-negative strains of V. parahaemolyticus, V. cholerae, two enteropathogenic strains of Escherichia coli, Shigella flexneri, and strains of salmonellae. Seven hours postchallenge, cardiac blood, liver, and spleen cultures were obtained. V. parahaemolyticus strains failed to induce intestinal fluid accumulation during this study period. Bacteremia occurred in animals challenged with Kanagawa-positive V. parahaemolyticus, S. flexneri, and salmonella strains only. Animal passage increased the ability of V. parahaemolyticus to cause bacteremia. Liver and spleen cultures were positive in approximately 50% of animals challenged with the Kanagawa-positive strains of V. parphaemolyticus. The ability of this organism to penetrate the intestinal epithelium of suckling rabbits may represent a specific property that plays a role in pathogenesis.
Insights
Kanagawa-positive Vibrio parahaemolyticus strains can cause bacteremia in rabbits, unlike other tested bacteria. Animal passage enhances this bacterium's ability to cause bacteremia, suggesting intestinal penetration is key to its pathogenesis.
Area of Science:
- Microbiology
- Pathogenesis
- Gastroenterology
Background:
- Vibrio parahaemolyticus is a marine bacterium causing diarrhea from seafood.
- Only beta-hemolytic (Kanagawa-positive) strains are enteropathogenic.
- Most marine V. parahaemolyticus isolates are nonhemolytic (Kanagawa-negative).
Purpose of the Study:
- To investigate the pathogenesis of Vibrio parahaemolyticus in a suckling rabbit model.
- To compare the invasive potential of Kanagawa-positive and negative strains.
Main Methods:
- Suckling rabbits were orally infected with various bacterial strains, including V. parahaemolyticus.
- Blood, liver, and spleen cultures were collected seven hours post-infection.
- Bacterial strains were passaged through animals to assess changes in virulence.
Main Results:
- V. parahaemolyticus did not induce intestinal fluid accumulation in this model.
- Bacteremia was observed with Kanagawa-positive V. parahaemolyticus, Shigella flexneri, and Salmonella strains.
- Animal passage increased V. parahaemolyticus bacteremia; liver and spleen cultures were positive in 50% of animals challenged with Kanagawa-positive strains.
Conclusions:
- Kanagawa-positive V. parahaemolyticus can invade the bloodstream and organs in suckling rabbits.
- The ability to penetrate the intestinal epithelium may be a critical factor in V. parahaemolyticus pathogenesis.
- Further research is needed to understand the mechanisms of V. parahaemolyticus invasion and disease.