Heat-Stable Enterotoxins Produced by Enteric Bacteria
Enterotoxigenic Escherichia coli produces two types of enterotoxin that cause diarrhea in humans and cattles. One is a high molecular weight heat-labile enterotoxin (LT) and the other is a low molecular weight heat-stable enterotoxin (ST). Two different kinds of ST have been described. One is STa or STI that is methanol soluble and active in suckling mice and piglets, but inactive in weaned pigs. The other is STb or STII that is methanol insoluble and active in weaned pigs, but inactive in suckling mice. At least two genetically distinct STa’s, that is STIa and STIb, have been reported. STIa and STIb also have been called STp and STh, respectively, because STIa and STIb were originally reported in E. coli isolated from pigs (and cows) and humans, respectively, although human isolates produce both STh and STp.
KeywordsDisulfide Bond Toxic Activity Enteric Bacterium Amino Acid Replacement Disulfide Bond Formation
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