Spores from mesophilic Bacillus cereus strains germinate better and grow faster in simulated gastro-intestinal conditions than spores from psychrotrophic strains

Abstract

The species Bacillus cereus, known for its ability to cause food borne disease, consists of a large variety of strains. An important property for discrimination of strains is their growth temperature range. Psychrotrophic strains can grow well at refrigerator temperatures but grow at 37 degrees C with difficulty. Mesophilic strains on the other hand are unable to grow below 10 degrees C, but grow well at 37 degrees C. Spores of six psychrotrophic and six mesophilic strains were investigated for their ability to survive and grow in simulated gastro-intestinal fluids, mimicking the conditions in the gastro-intestinal tract. The germination potential of psychrotrophic and mesophilic spores in simulated intestinal fluid does not differ much. Under conditions simulating the gastro-intestinal passage, 5 out of 6 mesophilic strains showed growth, and only 2 out of 6 psychrotrophic strains. Temperature (37 degrees C) and simulated gastro-intestinal conditions together influenced germination and growth.

Bacillus cereus NVH 0500/00 Can Adhere to Mucin but Cannot Produce Enterotoxins during Gastrointestinal Simulation

“…The bacteria remaining from the stomach simulation survived the bile and pancreatin treatment and resumed growth 2 h after exposure to these components. Although this behavior is consistent with that of other B. cereus strains (16,17), studies have shown that factors including bile concentration, pH, and food type may affect the responses of B. cereus to bile (12,14).…”

“…Incubation of B. cereus in the presence of microbial competition inhibits the outgrowth of germinated spores (15), and the effect is more pronounced when the intestinal bacteria are more abundant than B. cereus (16). Other studies have shown that spore germination and growth are possible during gastrointestinal simulations; however, enterotoxin production was not assessed (17). Enterotoxins, when produced, are unstable (6) and can be degraded rapidly in the presence of digestive enzymes (18,19).…”

Low Concentrations of Bile Salts Induce Stress Responses and Reduce Motility inBacillus cereusATCC 14570

“…Further, it has been shown that vegetative cells will not survive through the GI tract of humanflora-associated rats, while the spores do survive in the intestine of these rats (73). Finally, experiments recently published show that spores germinate in medium simulating the intestinal environment and that mesophilic strains germinate better than psychrotrophic strains in such medium (72). In this study we have also shown that the spores survive a high concentration (at least 1%) of bile salts.…”

Germination of Bacillus cereus Spores Is Induced by Germinants from Differentiated Caco-2 Cells, a Human Cell Line Mimicking the Epithelial Cells of the Small Intestine

“…Production and storage of spores were described previously (11). Culturing and differentiation of Caco-2 cells in 12-well plates using Dulbecco's modified Eagle medium (DMEM) (Gibco catalog no.…”

“…The 1-h procedure was used to establish adhesion and invasion; the 2-h procedure was used to investigate germination. After treatment with Triton X-100, the total and spore counts were determined as previously described (11). Similar adhesion-invasion and germination experiments were carried out in cell-free plates.…”