Traveller’s diarrhoea is most commonly caused by: (A) ETEC, (B) S. dysenteriae, (C) EPEC, (D) Salmonella
Answer is A. Five types of E.coli include:
1. ETEC (enterotoxogenic E.coli)
2. EIEC (enteroinvasive E.coli)
3. EPEC (enteropathogenic E.coli)
4. EHEC (enterohemorrhagic E.coli)
5. EAEC (enteroaggregative E.coli) 
Traveller's diarrhoea is most commonly caused by enterotoxogenic E.coli and then the other common organism responsible is S. dysenteriae. Intestinal Pathogenic E. Coli.