A microbiologist wants to develop a vaccine for preventation of attachment of diarrhoeagenic E.coli to the specific receptors in the gastro-intestinal tract. All of the following fimbrial adhesions would be appropriate vaccine candidates except -

Ans. is 'b' i.e.,P 1-Pili . P fimbriae are of impoance in urinary tract infection. They bind specifically to receptors present on the 'P' blood group antigen of human erythrocytes and uro-epithelial cells. They have no role in the attachment of diarrheogenic E. coli to the G.I. receptors. . E. coli posess fimbriae (type I) that mediate adhesion to a wide range of human and animal cells that contain the sugar mannose. Such adhesion is involved in the pathogenicity e.g. K-88 antigen found in strains causing enteritis in pigs. . K-99 antigen found in strains causing enteritis in calves and lambs. Colonization factor antigen CFAs expressed by ETEC. . CS, found in enterotoxigenic E. coli, it is a component of CFA-II. . A vaccine against these antigen will prevent adhesion of E. coli to the G.I. receptors and will prevent pathogenicity.