Submitted to: Clinical and Diagnostic Laboratory Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/1998
Publication Date: N/A
Interpretive Summary: The bacteria Escherichia coli is the most frequently identified cause of enteric disease in pigs. In order to cause disease, E. coli produce small hairlike structures (fimbriae) that allow them to stick to the surface of the intestine. After sticking to the intestine, these bacteria produce a variety of poisons that can result in either acute diarrhea or a chronic decreased rate of gain. We have developed a rapid diagnostic test that differentiates two closely related fimbriae, F18ab and F18ac. This test also showed a correlation with the fimbrial type and clinical signs; E. coli with F18ab fimbriae cause a chronic decreased rate of gain while E. coli with F18ac fimbriae cause diarrhea. We identified the parts of these two fimbriae that should be included in E. coli vaccines for pigs. The diagnostic test we developed will be useful for accurate disease diagnosis in swine and will allow vaccine companies to develop more effective E. coli vaccines. This will allow farmers to produce pork more efficiently, benefitting both farmers and consumers.
Technical Abstract: Toxin-producing Escherichia coli expressing F18 fimbriae colonize the small intestine of weaned pigs and cause diarrhea and/or edema disease. The F18 family is composed of two antigenic variants, F18ab and F18ac. Because many strains do not express F18 fimbriae in vitro, identification and differentiation of these two variants is difficult. Single-strand conformational polymorphism (SSCP) analysis is a rapid method for identifying genetic mutations and polymorphisms. The F18 major fimbrial subunit gene (fedA) of 136 strains was amplified by PCR and genetic differences were detected with SSCP analysis. The SSCP analysis of the fedA gene differentiated F18ab+ strains from F18ac+ strains. Most strains classified as F18ab+ by SSCP analysis contained Shiga toxin 2e and entertoxin genes. Most strains classified as F18ac+ by SSCP analysis contained only enterotoxin genes. The SSCP analysis of the virulence gene fedA was useful for predicting the antigenicity of F18+ E. coli and would be useful for analysis of other virulence genes in E. coli and other pathogenic bacteria.