Diagnosisand Investigation of Diarrheagenic Escherichia coli

Although most Escherichia coli are harmless commensals of the human intestine, certain specific, highly-adapted E. coli strains are capable of causing urinary tract, systemic or enteric/diarrheagenic infection. Diarrheagenic E coli are divided into six distinct categories, or pathotypes, each with a distinct pathogenic scheme (Table 1 ). Combined, diarrheagenic E coli have emerged as perhaps the most important enteric pathogens of man. In the developing world, the E coli categories account for more cases of gastroenteiltis among infants than any other cause (1 ) In addition, E coli are also the most common cause of traveller’s diarrhea, which afflicts more than one million travellers to the developing world annually (1 ). Enterohemorrhagic E coli (EHEC) are the cause of hemolytic uremic syndrome (HUS), which has become a major foodborne threat in many parts of the developed world (2 ).

Category	Toxins	Invasion	Virulence plasmid	Adhesin	Clinical syndrome
ETEC	LT, ST	—	Many	CFA/I, CFA/II, CFA/IV, others	Watery diarrhea
EPEC	—	+	60 MDa	Bundle-forming pilus	Watery diarrhea of infants
EHEC	SLT-1, SLT-2	—	60 MDa a	Intimin, Fimbriae a	Hemorrhagic colitis, HUS
EAEC	EAST1 a	?	65 MDa a	AAF/I, AAF/I	Watery, persistent diarrhea
EIEC	EIET a	+++	140 MDa	Ipa’s(?)	Watery diarrhea, dysentery
DAEC	?	?	?	F1845 a	Watery diarrhea