Comparative Sequence Analysis of Non-typable H Antigens of Pathogenic Shiga Toxin-producing Escherichia coli

Open Access
Fanelli, Samantha Lynn
Area of Honors:
Veterinary and Biomedical Sciences
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Chitrita Debroy, Thesis Supervisor
  • Dr. Lester C Griel Jr., Honors Advisor
  • Escherichia coli
  • E coli
  • bacteria
  • pathogenic
  • sequence analysis
  • H type
  • Shiga toxin
Escherichia coli bacteria populate a vast proportion of the gut, thus studying and appreciating the vast differences between strains would be to the benefit of the field of human medicine. Potentially pathogenic Shiga toxin-producing E. coli (n = 22) isolated from leafy green vegetables that could not be classified using standard H typing protocol, were analyzed in an attempt to determine if these strains were simply mutants or could be grouped together and classified as a new H type. The fliC gene, that encodes for the flagellar antigen, was amplified, sequenced, and comparative analyses were conducted to determine the similarities and differences in the sequences of this gene. Of these samples, 5 were almost identical in their fliC sequences. Further comparative analysis of the DNA sequences confirmed they were variants of the H7 serotype group that exhibited 26 base pair substitutions that resulted in 21 amino acid substitutions. This is an important finding, as it is a key to their mobility and potential pathogenicity and an indicator of the significance just a few base pair substitutions can have. This also opens doors for further research into the specific impact of amino acid substitutions on mobility and potential pathogenicity, in host species such as leafy vegetables.