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 whetherEscherichia colisurviving stresses encountered during a model dry-fermented sausage (DFS) production process exhibit enhanced tolerance and survival in anin vitrogastrointestinal model. Salami sausage batters spiked with fiveE. coliisolates, including enterohaemorrhagicE. colistrains 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 anin vitrodigestion challenge. Gastric exposure (pH 3) resulted in considerably reduced survival of theE. colistrains 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. colithat had undergone the DFS process showed about2.3 log10⁡​lower survival compared with those kept in sausage batter at 4°C. Our results indicated thatE. colistrains surviving a model DFS process exhibited reduced tolerance to subsequent gastric challenge at low pH.