Document Type

Thesis - University Access Only

Award Date

2007

Degree Name

Doctor of Philosophy (PhD)

Department / School

Veterinary and Biomedical Sciences

First Advisor

David H. Francis

Abstract

Various strains of Enterotoxigenic Escherichia coli (ETEC) may infect humans and domestic animals. Infection frequently results in perfuse watery and perhaps lifethreatening diarrhea. In swine, animals from birth through weaning may be affected. The colonization of ETEC in the small intestines is primarily mediated by fimbriae. Fimbriae are fiber-like protein structures, which are arrayed over the surface of the bacteria and confer ability to attach to the intestinal mucosa! surface receptors of susceptible host. Fimbria-mediated adherence enables ETEC to escape from mechanical clearance by peristaltic movement and facilitates rapid colonization of the intestine in high numbers. Thus, fimbriae are an essential virulence determinant of ETEC, and fimbriae-mediated bacterial adherence to small intestinal epithelial cells is the initial step in pathogenesis. The most common adhesin of porcine ETEC are K88. Three serological antigenic have been identified as receptors for K88ab and K88ad, respectively. Six different porcine enterocyte brush border phenotypes have been identified and are believed to be in consequence of the expression of various combinations of the three fimbrial receptors. K88 fimbriae contain multiple antigenic determinants, and amino acid composition analysis has shown sequence differences among the K88 variants. The objective of this study was characterization of the binding region of K88ad fimbrial protein. ETEC attachment was examined using an in vitro model system. Bacterial adherence assays were performed with two porcine intestinal epithelial cell lines (IPEC-1 and IPEC-12), and one human intestinal epithelial cell line (INT-407). E. coli expressing fimbrial adhesins K88ab, K88ac, K88ad, K99, F41, 987P, and Fl8 were used for adherence studies. E. coli expressing K88ab, K88ac, and K88ad bound equally to cells of IPEC-1 and IPEC-J2. The ETEC strain B41, expressing both K99 and F41, heavily bound to both porcine cell lines while the E.coli strain that expressed only K99 very weakly bound to these cells. E. coli expressing Fl8 strongly bound to IPEC-1 cells, but did not adhere to IPEC-J2 cells. E. coli strains G58-l and Kl2 which express no fimbrial adhesins failed to bind to either porcine cell line. E. coli that expressed 987P also failed to bind either porcine cell line. Only strains B41 and Kl2:K99 bound in abundance to INT407 cells.

Library of Congress Subject Headings

Intestines -- Infections. 
Escherichia coli infections in swine -- Pathogenesis. 
Monoclonal antibodies.      

Publisher

South Dakota State University

Download

Share

COinS
 

Rights Statement

In Copyright