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Pathogenesis of Vibrio parahaemolyticus: intraperitoneal and orogastric challenge experiments in mice
K Hoashi1, K Ogata, H Taniguchi
1Department of Microbiology, Oita Prefectural Institute of Health and Environment.
Abstract:
It has been noted that V. parahaemolyticus isolated from patients with food poisoning are almost always thermostable direct hemolysin (TDH)-positive, whereas, isolates from foods or environmental sources are usually TDH-negative. The virulence of V. parahaemolyticus in mice was examined by using intraperitoneal and orogastric challenge models, where the strains used were those isolated from patients and foods with food poisoning and included TDH-positive and -negative. The LD50 in mice was estimated to be approximately 10(7) in the former and 10(8) in the latter challenge model. In the mice killed by challenge, either intraperitoneal or orogastric, the following pathological changes were almost always observed: swelling, redness and fluid accumulation in the small intestine, particularly the upper part of it. Histologically, congestion, edema, and vacuolation were observed in mucosal and submucosal tissues; furthermore, ulceration at tips of some villi was noticed. The lethality and pathological finding in mice due to V. parahaemolyticus were demonstrated similarly in both challenge models and irrespective of the TDH phenotype of the strain used. It will be suggested that the findings in challenged mice may be attributed to enteropathogenic factor(s) other than TDH of V. parahaemolyticus.
Insights
Vibrio parahaemolyticus strains from patients are usually thermostable direct hemolysin (TDH)-positive, while environmental strains are TDH-negative. Mouse studies suggest other factors, not TDH, drive V. parahaemolyticus virulence and pathology.
Area of Science:
- Microbiology
- Pathogen Research
- Food Safety
Background:
- Vibrio parahaemolyticus is a significant cause of foodborne illness.
- Thermostable direct hemolysin (TDH) is often present in V. parahaemolyticus strains from human infections but typically absent in environmental isolates.
Purpose of the Study:
- To investigate the virulence of V. parahaemolyticus in mouse models.
- To compare the pathogenicity of TDH-positive and TDH-negative strains from clinical and food/environmental sources.
Main Methods:
- Virulence testing in mice using intraperitoneal and orogastric challenge models.
- Employing V. parahaemolyticus strains isolated from food poisoning patients and food/environmental sources.
- Assessing Lethal Dose 50 (LD50) and pathological changes in challenged mice.
Main Results:
- LD50 values were approximately 10^7 for clinical strains and 10^8 for food/environmental strains.
- Consistent pathological findings observed in mice, including small intestinal swelling, redness, fluid accumulation, congestion, edema, vacuolation, and villi ulceration.
- Lethality and observed pathology were similar across both challenge models and independent of the TDH phenotype.
Conclusions:
- The virulence and observed pathology of V. parahaemolyticus in mice are not solely dependent on the presence of TDH.
- Enteropathogenic factors other than TDH likely play a crucial role in V. parahaemolyticus-induced disease.