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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Characterization and Interventions for Foodborne Pathogens » Research » Publications at this Location » Publication #326911

Research Project: Molecular Characterization of Foodborne Pathogen Responses to Stress

Location: Characterization and Interventions for Foodborne Pathogens

Title: Characterization of shiga toxin subtypes and virulence genes in Porcine shiga toxin-producing Escherichia coli

item BARANZONI, GIAN MARCO - University Of Bologna, Italy
item Fratamico, Pina
item GANGIREDLA, JAYANTHI - Us Food & Drug Administration (FDA)
item PATEL, ISHA - Us Food & Drug Administration (FDA)
item Bagi, Lori
item DELANNOY, SABINE - University Of Paris
item FACH, PATRICK - The University Of Naples Federico Ii
item BOCCIA, FEDERICA - The University Of Naples Federico Ii
item ANASTASIO, ANIELLO - The University Of Naples Federico Ii
item PEPE, TIZIANA - The University Of Naples Federico Ii

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2016
Publication Date: 4/21/2016
Publication URL:
Citation: Baranzoni, G., Fratamico, P.M., Gangiredla, J., Patel, I., Bagi, L.K., Delannoy, S., Fach, P., Boccia, F., Anastasio, A., Pepe, T. 2016. Characterization of shiga toxin subtypes and virulence genes in Porcine shiga toxin-producing Escherichia coli. Frontiers in Microbiology. 7:574.

Interpretive Summary: Escherichia coli is a bacterium that lives in the intestinal tract of mammals including humans, and it is also found in food and the environment. The majority of E. coli are harmless; however, may cause human illness from mild diarrhea to more severe diseases or death. A group of harmful E. coli are known as Shiga toxin-producing E. coli (STEC) due to their ability to produce one or more potent toxins belonging to the Shiga toxin (Stx) family. Cattle are known to carry STEC in their GI tract, and studies have been conducted to examine the characteristics of cattle STEC; however, less is known about STEC carried by swine. In this investigation, state-of-the-art DNA-based technologies were used to determine the disease-causing potential of 181 STEC strains recovered from healthy pigs. Some of the strains carried certain virulence genes involved in attachment to cells, as well as other genes, including those that are involved in the production of Shiga toxin types (Stx1a and Stx2d) that are linked to strains that cause severe human illness. The results of this study enhance the understanding of STEC carried by swine and their potential to cause human illness, and thus provide information for risk assessments and for development of control strategies.

Technical Abstract: Similar to ruminants, swine have been shown to be a reservoir for Shiga toxin-producing Escherichia coli (STEC), and pork products have been linked with outbreaks associated with STEC O157 and O111:H-. STEC strains, isolated in a previous study from fecal samples of late-finisher pigs, belonged to a total of 56 serotypes, including O15:H27, O91:H14, and other serogroups previously associated with human illness. The isolates were tested by PCR and a high-throughput real-time PCR system to determine the Shiga toxin subtype and virulence-associated and putative virulence-associated genes they carried. Select STEC strains were further analyzed using a Minimal Signature E. coli Array Strip (FDA-ECID). As expected, stx2e (81%) was the most common Shiga toxin variant, followed by stx1a (14%), stx2d (3%) and stx1c (1%). The STEC serogroups that carried stx2d were O15:H27, O159:H16 and O159:H-. Similar to stx2a and stx2c, the stx2d variant is associated with development of hemorrhagic colitis and hemolytic uremic syndrome, and reports on the presence of this variant in STEC strains isolated from swine are lacking. Moreover, the genes encoding heat stable toxin (estIa) and enteroaggregative Escherichia coli heat stable enterotoxin-1 (astA) were commonly found in 50% and 44% of isolates, respectively. The hemolysin genes, hlyA and ehxA, were both detected in 7% of the swine STEC strains. Although the eae gene was not found, other genes involved in host cell adhesion, including lpfAO113 and paa were detected in more than 50% of swine STEC strains, and a number of strains also carried iha, lpfAO26, lpfAO157, fedA, orfA, and orfB. The present work provides new insights on the distribution of virulence factors among swine STEC strains and shows that swine may carry Stx1a-, Stx2e- or Stx2d-producing E. coli with virulence gene profiles associated with human infections.