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.
University of Minnesota M.S. thesis. Major: Comparative and molecular biosciences. Advisor: Dr. Timothy Johnson. 1 computer file (PDF); vi, 79 pages.
Shepard, Sara Maria.
Phylogenetic and genomic characterization of porcine enterotoxigenic Escherichia coli.
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