title: Characterization of Shiga Toxin Subtypes and Virulence Genes in Porcine Shiga Toxin-Producing Escherichia coli.
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 polymerase chain reaction (PCR) and a high-throughput real-time PCR system to determine the Shiga toxin (Stx) 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. As expected, stx 2e (81%) was the most common Stx variant, followed by stx 1a (14%), stx 2d (3%), and stx 1c (1%). The STEC serogroups that carried stx 2d were O15:H27, O159:H16 and O159:H-. Similar to stx 2a and stx 2c, the stx 2d 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 E. 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.
authors.affiliation: Eastern Regional Research Center, United States Department of Agriculture - Agricultural Research Service Wyndmoor, PA, USA.
authors.forename: Gian Marco
authors.initials: GM
authors.lastname: Baranzoni
authors.affiliation: Eastern Regional Research Center, United States Department of Agriculture - Agricultural Research Service Wyndmoor, PA, USA.
authors.forename: Pina M
authors.initials: PM
authors.lastname: Fratamico
authors.affiliation: Center of Food Safety and Applied Nutrition, U.S. Food and Drug Administration Laurel, MD, USA.
authors.forename: Jayanthi
authors.initials: J
authors.lastname: Gangiredla
authors.affiliation: Center of Food Safety and Applied Nutrition, U.S. Food and Drug Administration Laurel, MD, USA.
authors.forename: Isha
authors.initials: I
authors.lastname: Patel
authors.affiliation: Eastern Regional Research Center, United States Department of Agriculture - Agricultural Research Service Wyndmoor, PA, USA.
authors.forename: Lori K
authors.initials: LK
authors.lastname: Bagi
authors.affiliation: Food Safety Laboratory, University of Paris-Est, Anses, Maisons-Alfort France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Delannoy
authors.affiliation: Food Safety Laboratory, University of Paris-Est, Anses, Maisons-Alfort France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Fach
authors.affiliation: Department of Veterinary Medicine and Animal Production, University of Naples Federico II, Naples Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Boccia
authors.affiliation: Department of Veterinary Medicine and Animal Production, University of Naples Federico II, Naples Italy.
authors.forename: Aniello
authors.initials: A
authors.lastname: Anastasio
authors.affiliation: Department of Veterinary Medicine and Animal Production, University of Naples Federico II, Naples Italy.
authors.forename: Tiziana
authors.initials: T
authors.lastname: Pepe
keywords: Escherichia coli; STEC; Shiga toxins variants; swine; virulence genes