How can this bacterium E.coli be the etiologic agent of most cases of traveler's diarrhea?

Question

It is normally found in the large intestines of humans. In reguards to microbiology.

Answer 1

Actually, enterotoxigenic E. coli IS the commonest cause of travelers diarrhea, according the the Centres for Disease Control. Other bacteria are also significant causes, as are some viruses and parasites.

http://www.cdc.gov/ncidod/dbmd/diseaseinfo/travelersdiarrhea_g.htm#causes

But Gumdrop Girl is right that there are many, many different strains of E coli, and the commonest strains vary from place to place. Therefore, if you travel to a new place, chances are you won't be immune to the local versions of E coli.

Answer 2

E. coli is NOT the etiological agent for most cases of travelers' diarrhea. Salmonella, Shigella and Campylobacter comprise more cases of bacterial enteric infections than E. coli.

But if we must speak of E. coli, you must realize that E. coli is a large species with a lot of subspecies. Not all E. coli is pathogenic. Particularly of note are the strains symbiotic to humans -- they won't hurt us. But there are a few strains that are very unpleasant, if not dangerous to humans. There are STEC, EHEC, VTEC and ETEC strains.

STEC = Shiga-toxin producing E. coli
EHEC = enterohemorrhagic E. coli
VTEC = verotoxin-producing E. coli
ETEC = eterotoxic E. coli

Each of these pathogenic E. coli strains works by a different mechanism. All are found in feces (though not all fecal matter is carrying these strains).

Answer 3

Thank you, Gumdrop, for your very fine answer to this question.