Shepard, Sara Maria2011-10-272011-10-272011-08https://hdl.handle.net/11299/117199University of Minnesota M.S. thesis. Major: Comparative and molecular biosciences. Advisor: Dr. Timothy Johnson. 1 computer file (PDF); vi, 79 pages.Porcine enterotoxigenic Escherichia coli (ETEC) is a significant pathogen of young pigs, causing considerable morbidity and mortality. While the known plasmidencoded virulence factors related to porcine ETEC infection have been well-studied, the chromosomal background of porcine ETEC has been largely understudied. Since chromosomal backgrounds and any chromosome-encoded virulence factors may directly or indirectly influence ETEC pathogenesis, they deserve attention. In this study, we utilized the first completed genome sequences of porcine ETEC to better understand porcine ETEC chromosomal content. We first examined the porcine ETEC chromosome by performing multilocus sequence analysis on 80 different porcine ETEC isolates implicated in neonatal and post-weaning diarrhea. We found that the porcine ETEC examined clustered into several specific lineages, suggesting the acquisition of porcine ETEC virulence plasmids into different E. coli chromosomal lineages on multiple occasions. These results also suggest that only certain chromosomal backgrounds support successful ETEC-related plasmid carriage. Patterns in resistance and virulence plasmid carriage were less clear, with plasmids of interest distributed widely among the isolates. Additionally, we used predictive software to identify putative surface-expressed proteins with predicted high antigenicity from the completed genome of UMNK88, a K88-positive porcine ETEC. The prevalence of these genes was examined in porcine ETEC strains and in commensal E. coli from healthy pigs. Genes found in ETEC significantly more often than in commensal E. coli include Antigen 43 precursor protein, tatD, and several other putative outer membrane or exported proteins.en-USComparative and molecular biosciencesThesis or Dissertation