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Cytotoxicity and suckling mouse reactivity of Aeromonas hydrophila isolated from human sources
Abstract:
Human isolates of Aeromonas hydrophila and Plesiomonas shigelloides were tested for their ability to produce cytotoxins and (or) enterotoxins. The incidence of cytotoxin production by A. hydrophila was 81% for isolates from stool and 44% for extraintestinal isolates. Chinese hamster ovary (CHO) cells were more sensitive to A. hydrophila cytotoxin than either Vero or Y-1 mouse adrenal tumor cells (y-1). There was no evidence of cytotonic enterotoxin production by any of the isolates tested. Cytotoxin-containing filtrates from A. hydrophila were found to provoke a positive reaction in suckling mice. The response in mice was heat labile, and data supporting correlation of this activity with the cytotoxin produced by these organisms are presented. Following concentration, cytotoxin and material reactive in suckling mice were found to coelute from Sephadex G-25 and dose-response was demonstrated in mice. Antitoxin prepared to this material effectively neutralized cytotoxin, mouse reactivity, and rabbit ileal loop response. No evidence was obtained for either cytotoxin or enterotoxin production by P. shigelloides strains tested in this study.
Insights
Aeromonas hydrophila produces a heat-labile cytotoxin, but Plesiomonas shigelloides does not. This cytotoxin, identified in human isolates, causes reactions in suckling mice and is neutralized by specific antitoxin.
Area of Science:
- Microbiology
- Bacteriology
- Toxicology
Background:
- Aeromonas hydrophila and Plesiomonas shigelloides are common bacteria.
- Understanding their toxin production is crucial for public health.
- Previous research on their enterotoxigenicity is varied.
Purpose of the Study:
- To investigate the production of cytotoxins and enterotoxins by human isolates of A. hydrophila and P. shigelloides.
- To characterize the cytotoxic activity and its effects in animal models.
- To determine the correlation between cytotoxin and observed mouse reactivity.
Main Methods:
- Bacterial isolates from human stool and extraintestinal sources were cultured.
- Toxin production was assessed using Chinese hamster ovary (CHO), Vero, and Y-1 mouse adrenal tumor cells.
- Suckling mice and rabbit ileal loop models were used to evaluate toxin effects.
- Purification and characterization of cytotoxin were performed using Sephadex G-25 chromatography.
- Neutralization assays with specific antitoxin were conducted.
Main Results:
- 81% of stool isolates and 44% of extraintestinal isolates of A. hydrophila produced cytotoxin.
- CHO cells were most sensitive to A. hydrophila cytotoxin.
- No cytotonic enterotoxin production was detected in any isolates.
- Cytotoxin-positive filtrates induced heat-labile reactions in suckling mice.
- Purified cytotoxin coeluted with mouse-reactive material and demonstrated dose-response in mice.
- Antitoxin neutralized cytotoxin, mouse reactivity, and rabbit ileal loop response.
- No cytotoxin or enterotoxin production was found in P. shigelloides isolates.
Conclusions:
- A. hydrophila produces a significant cytotoxin, particularly in stool isolates, which is responsible for observed mouse reactivity.
- P. shigelloides does not appear to produce cytotoxins or enterotoxins.
- The characterized cytotoxin has implications for understanding A. hydrophila pathogenicity.