Interactions between pathogenic Escherichia coli, porcine intestinal cells, and a phytogenic feed additive and its main active substance

Plant derived products are claimed to improve animal performance and health, but the knowledge on the mode of action is still limited. The aim was to investigate effects of a phytogenic feed additive and its main active substance in vitro regarding 1) their impact on adhesion properties of F4+ Escherichia coli to the porcine intestinal epithelial cell line IPEC-J2, 2) their capacity to bind E. coli, and 3) their antimicrobial character in context to the pathogenic E. coli. The phytogenic additive Fresta®F (FF; Delacon, Austria) consists of essential oils, herbs, and spices. The main ingredient of the additive consists of 28% galactomannans (GM). The impact of the test substances was investigated in vitro by measuring the fluorescence intensity of CDFA-SE marked bacteria that adhere on the IPEC-J2 cells (trial #1). A flow cytometer was used to quantify the fluorescent cells. In vitro trial #2 was performed using a coating method previously published by Becker et al. 2007. Antimicrobial effects of FF and GM on the E. coli strain were estimated semi-quantitatively from bacterial growth curves. FF and GM significantly reduced the adhesion of E. coli to IPEC-J2 (p<0.05); fluorescence intensity was 0.96±0.63, 0.86±0.61, and 2.03±1.13, respectively. FF 0.37±0.20 and GM 0.42±0.16 showed capacity to bind E. coli compared with the positive control 0.52±0.05. No direct antimicrobial effects could be detected. It is concluded that the mode of action of Fresta®F is not due to antimicrobial effect, but rather due to the anti-adhesion capacity of galactomannans present in the products main component.

References: 1. Becker, P.M., et al. (2007)J Appl Microbiol 103, 2686–2696.