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P2-12 Characterization of the Virulence Plasmid p7v Harbored in an STEC/ETEC Hybrid Pathotype Escherichia sp. Isolate

Tuesday, August 5, 2014
Exhibit Hall D (Indiana Convention Center)
Susan Leonard, U.S. Food and Drug Administration, Laurel, MD
David Lacher, U.S. Food and Drug Administration, Laurel, MD
Mark Mammel, U.S. Food and Drug Administration, Laurel, MD
Michael Kotewicz, U.S. Food and Drug Administration, Laurel, MD
Christopher Elkins, U.S. Food and Drug Administration, Laurel, MD
Introduction: Escherichia coli harboring virulence genes from more than one pathotype have been isolated and these hybrid pathotypes may give rise to new emerging pathogens, such as the case of the 2011 German EAEC/STEC O104:H4 strain. Hybrid STEC/ETEC isolates, encoding both Shiga toxin and heat stable enterotoxin, have been isolated from multiple sources, but have not been well studied. Virulence genes can be transferred between strains via mobile genetic elements such as plasmids; therefore, characterization of plasmids carried by hybrid pathotypes is important for elucidating the evolutionary processes involved in the emergence of new pathotypes.

Purpose: The objective of this study was to characterize the novel virulence plasmid carried by the Shiga toxin-producing Escherichia sp. cryptic lineage I O2:H25 strain 7v that is known to also encode heat stable enterotoxin.

Methods: Plasmid DNA was extracted from Escherichia sp. 7v and sequenced. Contigs were joined using PCR where necessary to yield a continuous sequence. Phylogenetic analysis utilizing more than 200,000 backbone SNPs from whole genome sequences was performed to place the 7v strain in context with other STEC/ETEC hybrid pathotype isolates as well as prototype strains from additional representative E. coli pathotypes.

Results: Plasmid p7v is 229,275 bp in size, contains 340 coding sequences, and harbors the astA gene encoding the EAST1 toxin as well as two copies of the gene encoding heat stable enterotoxin STa. Virulence genes more typical of STEC strains, including katP, ehxA, and espP, are also carried on p7v and, in addition, sequence analysis revealed regions encoding conjugative transfer and several metabolic processes. Phylogenetic analysis revealed a wide diversity of genomic backbones associated with hybrid STEC/ETEC isolates.

Significance: Characterization of strains at the STEC/ETEC pathotype intersection may aid in more rapid detection, identification, and outbreak risk assessment of these emerging threats to the food supply and human health.

Back to: Poster Session - Pathogens, Epidemiology, Novel Laboratory Methods, Food Defense, Communication Outreach and Education, General Microbiology, Dairy and Other Food Commodities, Food Toxicology
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