Virulence Potential of Activatable Shiga Toxin 2d-Producing Escherichia coli Isolates from Fresh Produce

Abstract

Shiga toxin (Stx)–producing Escherichia coli (STEC) strains are food- and waterborne pathogens that are often transmitted via beef products or fresh produce. STEC strains cause both sporadic infections and outbreaks, which may result in hemorrhagic colitis and hemolytic uremic syndrome. STEC strains may elaborate Stx1, Stx2, and/or subtypes of those toxins. Epidemiological evidence indicates that STEC that produce subtypes Stx2a, Stx2c, and/or Stx2d are more often associated with serious illness. The Stx2d subtype becomes more toxic to Vero cells after incubation with intestinal mucus or elastase, a process named “activation.” Stx2d is not generally found in the E. coli serotypes most commonly connected to STEC outbreaks. However, STEC strains that are stx2d positive can be isolated from foods, an occurrence that gives rise to the question of whether those food isolates are potential human pathogens. In this study, we examined 14 STEC strains from fresh produce that were stx2d positive and found that they all produced the mucus-activatable Stx2d and that a subset of the strains tested were virulent in streptomycin-treated mice.

Shiga toxin-producing Escherichia coli (STEC) O22:H8 isolated from cattle reduces E. coli O157:H7 adherence in vitro and in vivo

“…The presence of the Stx2d subtype has been described in some O22:H8 strains (Beutin et al, 2007) and it has been shown that potentially highly pathogenic strains producing Stx2d activatable are eae-negative (Bielaszewska et al, 2006) although their relevance in human illnesses is moderate (Melton-Celsa et al, 2015). We have observed an increased cytotoxic activity of Stx2 after incubation with mucus, suggesting that this subtype might play an important role in pathogenesis.…”

Immunization of mice with chimeric antigens displaying selected epitopes confers protection against intestinal colonization and renal damage caused by Shiga toxin-producingEscherichia coli

“…In streptomycin-treated mice, Stx2d-producing E. coli strains have been shown to affect renal function leading to death. 32, 33 For instance, in a previous study we showed that the Stx2d-producing E. coli O91:H21 str. V07-4-4 is lethal to mice when they are orally inoculated with a dose of 10 9 CFU.…”

Immunization of mice with chimeric antigens displaying selected epitopes confers protection against intestinal colonization and renal damage caused by Shiga toxin-producing Escherichia coli

“…Kidney damage is one of the most severe clinical outcomes that can occur during STEC infection due to the action of Shiga toxins. In streptomycin-treated mice, Stx2d-producing E. coli strains have been shown to affect renal function leading to death 34,35 . For instance, in a previous study we showed that the Stx2d-producing E. coli O91:H21 str.…”