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Title: Comparison of O-antigen gene cluster from E. coli O157 from human and non-human strains

Author
item SILVA, N.C.C. - Universidad De Sao Paulo
item CASTILLO, C.J.C. - Universidad De Sao Paulo
item Bono, James - Jim

Submitted to: Biomicroworld Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2015
Publication Date: 10/28/2015
Citation: Silva, N., Castillo, C., Bono, J.L. 2015. Comparison of O-antigen gene cluster from E. coli O157 from human and non-human strains. [abstract] Biomicroworld Proceedings. Session:7, code 609. Available: http://www.formatex.info/biomicroworld2015/acceptedabstracts.php

Interpretive Summary:

Technical Abstract: Shiga toxin-containing Escherichia coli O157:H7 (STEC O157:H7) is an important zoonotic pathogen which can be transmitted to humans by ingestion of contaminated water or food. Cattle are a common reservoir for STEC O157:H7. This microorganism may cause diarrhea, bloody diarrhea, and hemolytic-uremic syndrome if ingested by humans. The proposed evolutionary pathway for STEC O157:H7 suggests that this organism has a hybrid chromosome with the majority of the chromosome originating from E. coli O55:H7 and only the O157 antigen synthesis gene cluster from E. coli O157. Therefore, DNA targets from the O157 O-antigen synthesis gene cluster could potentially be specific for STEC O157. However the O157 O-antigen synthesis gene cluster are shared with all E. coli O157 regardless of its H serotype. We hypothesized that single nucleotide polymorphisms (SNP) unique to STEC O157 would be found in the O157 O-antigen synthesis gene cluster that could be used for identifying STEC O157 from E. coli O157 non-H7 strains. To compare the O-antigen synthesis gene cluster from STEC O157:H7 and O157 non-H7 strains, 191strains isolated from human, cattle, pig, rabbit, fly and ground beef were sequenced using the Illumina Miseq platform. One-hundred forty eight STEC O157:H7 strains and forty three O157 non-H7 strains were mapped to the Sakai genome (NC002695) using Geneious mapper to create a mapped consensus derived genome for each strain. The consensus derived genomes were then aligned and a phylogenetic tree made using Parsnp. The aligned strains were found to group almost exclusively by H-type. Eighty-eight SNPs differences were identified in the O antigen synthesis genes that differentiated STEC O157:H7 strains from O157 non-H7 strains. These SNPs represent excellent candidates for developing single target assays for STEC O157, however testing with additional strains will be needed to validate the SNP targets. Additionally, a SNP was identified in the STEC O157:H7 strains that is in linkage disequilibrium with the tir A>T polymorphism, a genetic marker that associates with the ability of a strain to cause disease in humans. These results support previous findings of allelic differences between STEC O157:H7 and O157 non-H7 in conserved genes, but also demonstrate the diversity of O157 isolates.