Effect of acid-adaptation on Listeria monocytogenes survival and translocation in a murine intragastric infection model

Abstract

Acid tolerance response mechanisms can greatly influence Listeria monocytogenes survival in low pH foods. In the present paper, the effect of acid-adaptation together with control of gastric pH level on L. monocytogenes survival and translocation was analyzed after intragastric inoculation in the BALB/c mouse model. Our results showed that acid-adaptation led to an increase in resistance to the first barrier constituted by the low gastric pH and that inoculation at alkaline pH had a synergistic effect. It resulted in a higher live bacterial load reaching the next intestinal compartments and was correlated with increased translocation rates to the mesenteric lymph nodes, both at the frequency and quantitative levels. Our results in this murine model suggest that acid-adaptation of L. monocytogenes in low pH foods, together with control of gastric pH level through dietary practices, or use of inhibitors of gastric acid secretion, may be potential aggravating risk factors to food-borne listeriosis. ß

Effect of Acid Adaptation on the Fate of Listeria monocytogenes in THP-1 Human Macrophages Activated by Gamma Interferon

“…We previously demonstrated that the expression of virulence determinants of L. monocytogenes can be influenced by low temperature and iron deficiency (10,11,12). Sensing an acidic environment, as that encountered by the bacterium during passage through the gastrointestinal tract, can be considered an additional stimulus triggering expression of the virulent phenotype, and this is consistent with the evidence that induction of the ATR enhances the survival of L. monocytogenes both in vitro and in vivo (9,16,39,43,49). Acid-tolerant variants have increased lethality for mice when inoculated by the intraperitoneal route (43).…”

“…As in other bacteria, the ATR in L. monocytogenes has been shown to require a two-component signal transduction system, which is essential for sensing different environmental stresses (15). Both the acid shock response and the ATR have been suggested to promote L. monocytogenes survival in acidic foods (9) and in gastric fluids (16), thereby contributing to the ability of this bacterium to cause infection (49).…”

“…While robust evidence linking the ATR with virulence has been obtained (39,43,49), the underlying molecular circuitry and the behavior of acid-stressed bacteria within host cells are not yet well known. Following penetration of the gut epithelium, the multiplication of L. monocytogenes in macrophages contributes to its spread to various target tissues (14,21,22,38).…”

Surviving the Acid Test: Responses of Gram-Positive Bacteria to Low pH

“…A neutropenic-mouse model was used to demonstrate that oral administration of sodium bicarbonate shortly before intragastric inoculation significantly increased the severity of the resulting systemic infection by L. monocytogenes strain EGD (64). When the murine gastric pH was lowered through the use of acidified water, it was observed that acid-adapted cells enjoyed increased resistance relative to their unadapted counterparts (198). These results suggest that control of gastric pH through dietary practices or use of inhibitors of gastric acid secretion may be potential aggravating risk factors for food-borne listeriosis.…”

“…In these circumstances, the number of aerobes, anaerobes, and coliforms increases so that there is overgrowth of bacteria in the stomach. It has also been observed that neutralization of acid by food or bicarbonate decreases the infectious dose; for example, an increase in the pH of the stomach results in gastric transit of greater numbers of Listeria (44,63,64,198,205,258) while gastrectomy and chronic gastritis are risk factors for the development of intestinal tuberculosis (62). Interestingly, preadaptation under conditions similar to those encountered by Mycobacterium avium in its natural habitat allows the organisms to resist the acidic conditions of the stomach (20).…”