Survival of Five Strains of Shiga ToxigenicEscherichia coliin a Sausage Fermentation Model and Subsequent Sensitivity to Stress from Gastric Acid and Intestinal Fluid

Abstract

The ability of foodborne pathogens to exhibit adaptive responses to stressful conditions in foods may enhance their survival when passing through the gastrointestinal system. We aimed to determine whether Escherichia coli surviving stresses encountered during a model dry-fermented sausage (DFS) production process exhibit enhanced tolerance and survival in an in vitro gastrointestinal model. Salami sausage batters spiked with five E. coli isolates, including enterohaemorrhagic E. coli strains isolated from different DFS outbreaks, were fermented in a model DFS process (20°C, 21 days). Control batters spiked with the same strains were stored at 4°C for the same period. Samples from matured model sausages and controls were thereafter exposed to an in vitro digestion challenge. Gastric exposure (pH 3) resulted in considerably reduced survival of the E. coli strains that had undergone the model DFS process. This reduction continued after entering intestinal challenge (pH 8), but growth resumed after 120 min. When subjected to gastric challenge for 120 min, E. coli that had undergone the DFS process showed about 2.3 log10⁡ lower survival compared with those kept in sausage batter at 4°C. Our results indicated that E. coli strains surviving a model DFS process exhibited reduced tolerance to subsequent gastric challenge at low pH.

Determination of the changes in the gastric fluid endurance of O157 and non-O157 Shiga toxin-producing Escherichia coli during storage of experimentally produced beef frankfurter

“…The stress responses of STEC pathogens, as the results indicated in the present study, might differ when food is introduced in the acid challenges. Rode et al (2017), investigated the survival of STEC strains in a digestion challenge after sausage fermentation and they reported non-O157 isolates had survival patterns similar to that of O157 strains. Miszczycha et al (2014), reported the fate of STEC O157 and O26 during a digestion challenge of contaminated cheeses was dependent on the strain and O26 survived significantly better than O157.…”