Study of the ability of Bacillus toyonensis to interfere with the quorum-sensing systems of enterotoxigenic Escherichia coli K88 in the pig gut

© 2016 American Society of Animal Science. All rights reserved. Hypothesis: The probiotic strain Bacillus toyonensis (Toyo) may interfere with the quorum-sensing (QS) mechanisms of Escherichia coli (ETEC) K88. Three different in vitro approaches were performed. Materials and methods: Trial 1: The adhesiveness of ETEC-K88 was evaluated using porcine intestinal epithelial cells (IPEC-J2). Bacteria were grown in the ileal and the colonic sterile digesta supernatants (SN) obtained from 32 weaned piglets supplemented (TREAT) or not (CTR) with Toyo (109CFU/g) and subsequently added to IPEC-J2. Trial 2: Using a similar model to Trial 1, E. coli was grown in media including sterile SN obtained from cultures of E. coli coincubated or not with Toyo or sterile SN from Toyo incubated or not with acyl-homoserine lactone (AHL). Trial 3: The gene expression of the fimbrial adhesin (F4) and the heat-labile enterotoxin (LT) of ETEC-K88 was also determined after different treatments. Results: The incubation of bacteria with the ileal TREAT leads to a reduction in the adhesion of E. coli (P = 0.06). As expected, ETEC-K88 grown with its own SN increased its ability to colonize the epithelium (P = 0.023), which was slightly reduced by Toyo. Gene expression results suggest that Toyo was able to reduce the expression of F4 induced by the ETEC-K88 SN (0.64-fold changes). Moreover, when ETEC-K88 is grown in the supernatant of a previous culture of Toyo with AHL or it is cocultured with Toyo in the presence of AHL, the expressions of F4 (0.61-fold changes) or LT (0.67-fold changes) were also reduced, respectively. Conclusion: These results suggest the ability of B. toyonensis to act on the QS systems of ETEC-K88 by different complex mechanisms.