Comparative effects of cholera toxin, Salmonella typhimurium culture lysate, and viable Salmonella typhimurium in isolated colon segments in ponies.

This research attempted to evaluate the impact of cholera toxin, Salmonella typhimurium culture lysate, and live Salmonella typhimurium in parts of the colon in ponies. The article reveals an increase in fluid accumulation with cholera toxin and Salmonella lysate but not with live Salmonella or the control solution. It was also found that cyclic adenosine monophosphate levels were lower in the inoculated segments.

Experimental Procedure

• In this experiment, isolated sections of the left dorsal colon, as well as a side-to-side colocolostomy between the left ventral colon and left dorsal colon, were surgically crafted in 6 adult ponies.
• Each pony had four separate segments, each punctuated by a clear segment. These were injected (20 ml) with one of four distinct solutions: a phosphate buffered saline solution (PBSS)/1% polyethylene glycol (PEG); cholera toxin in PBSS/1% PEG; Salmonella typhimurium UCD 1755 culture lysate mixed in PBSS/1% PEG; and live Salmonella typhimurium UCD 1755.

Key Observations

• After 20 hours, the ponies were reanesthetized and the fluid within the colon segments was measured. Tissue samples from the segments were also extracted for light and electron microscopic examination and for measurement of mucosal cyclic adenosine monophosphate levels.
• The segments exposed to cholera toxin in 4 ponies resulted in a significant fluid buildup (29.5 +/- 12.7 ml), and exposure to the S. typhimurium UCD 1755 culture lysate in 3 ponies also caused fluid accumulation (14.0 +/- 8.7 ml).
• No fluid buildup was observed in segments treated with the control solution (PBSS/1% PEG) or the live Salmonella typhimurium UCD 1755.
• Furthermore, the levels of cyclic adenosine monophosphate were significantly lower in segments exposed to cholera toxin, Salmonella lysate, and the live Salmonella, relative to the control segments.

Conclusions

• The results indicate a notable reaction to the cholera toxin and the S. typhimurium UCD 1755 culture lysate but not to the live Salmonella or the control fluid. This could potentially offer insights into the varying impacts and mechanisms by which different toxins and bacteria affect the equine colon.