E coli causing hemolytic uremic syndrome -
Ans. is 'd' i.e., Enterohemorrhagic ESCHERICHIA COLIAt least six distinct "pathotypes" of intestinal pathogenic E. coli exist:o Enteropathoaenic E. coli [Entcroadherent E. colilIt causes diarrhoea in infants and children usually occuring as institutional out breaks.It does not produce enterotoxin, nor are they invasive. They adhere to the mucosa of small intestine and cause disruption of the brush border microvilli.These strains can be identified by their adhesion to HEP - 2 cells.o Enterotoxigenic E.coliIt causes traveller's diarrhoea [ETEC is the most common cause of traveller's diarrhea).It produces enterotoxins. They can produce heat labile toxin (LT) or heat stable toxin or both.Toxin production alone may not lead to illness. The strain should first be able to adhere to intestinal mucosa. This adhesiveness is medicated by fimbrial or colonisation factor antigen (CFA).o Enteroinvasive E. coliThey themselves resemble shigella and their infection resembles shigellosis (remember : shiga like toxin is elaborated by enterohemorrhagic E. coli).They produce mild diarrhoea to frank dvsentry and occur in adult as well as in children.They have been termed enteroinvasive because they have the capacity to invade intestinal epithelial cells in vivo and penetrate HeLa or HEP - 2 cells in tissue culture.This ability of penetration is plasmid determined which codes for outer membrane antigens called the Hirulence marker antigen" (VMA). The detection of plasmid can be diagnostic.For laboratory diagnosis of EIEC, the sereny test used to be employed.These strains are non motile, do not ferment lactose or ferment it late with acid without producing any gas.o Enterohemorrhagic E. coli or verotoxigenic E. coliThese strains produce verocytotoxin (VT) or shiga like toxin (SLT)They can cause mild diarrhoea to fatal hemorrhagic colitis.Shiga like toxin belongs to class ribosome inactivating proteins (RIPs). It inhibits protein synthesis by inhibiting ribosomal function.This toxin also acts on vascular endothelium to promote the synthesis of coagulation factor VIII, vWF - Platelet aggregation.They can cause hemolytic uremic syndrome particularly in young children and the elderly.O 157 : H 7 is the most prominent serotype of EHEC, associated with HUS, but 06,026,055,091,0103,0111,0113 and OX3 have also been associated with this syndrome.The primary target for V.T is vascular endothelium.The typical EHEC is serotype O157 : H7 which does not ferement sorbital unlike majority of E. coli (but Harrison writes that few species of this serotype can ferment sorbital).Some other serotype like O26 : H1 also belongs to this group.Laboratory diagnosis of VIEC diarrhea is established by demonstration of the bacilli or VT in feces directly or in culture.o Enteroaggrecative E. coli}# In developing countries and young children.# Can cause traveller's diarrhea and persistent diarrhea.# In vitro, thev exhibit a "stacked - brick" adherence pattern on Hep - 2 cells.o Diffusely adherent E. coli# Enteroaggregative E. coli forms a low molecular weight heat stable enterotoxin EAST -1 (enteroaggregative heat stable enterotoxin -1).
Enteropathogenic
Enterotoxigenic
Enteroinvasive
Enterohemorrhagic
Bacteria