ISSUE FOCUS 44 FEED & ADDITIVE MAGAZINE November 2022 of bacteria to the antimicrobials and are commonly used to test alternatives to antibiotics. When evaluating the antimicrobial effect of a blend of fatty acid esters solution, it appeared particularly efficient toward Gram positive bacteria, with MICs value ranged from 32 ppm for Clostridium perfringens to 250 ppm for Streptococcus suis and Campylobacter jejuni (Table 1). By limiting the colonization on epithelial cells, the specific association of different fatty acids esters allowed to broaden the spectra of action specially toward Gram negative bacteria, such as Salmonella spp., a main issue in a sanitary point of view. Bacterial competition assays were carried out in order to evaluate the capacity of the fatty acid esters blend to limit the adhesion of strains of S. Typhimurium, E. coli and C. jejuni on HT-29 intestinal cells. For this, the blend was introduced simultaneously with the bacterial strains then left in contact for 2 hours. For each of the strains tested, the percentage of adhesion varied from 30% to 55% compared to the control (without fatty acid esters). This result highlights that the tested solution significantly reduces the proportion of bacteria adhered to intestinal cells (Figure 1). Another key component of gut health is the effect of solution on inflammation. An overreaction of the immune system consumes energy that would otherwise have been used for animal growth. A positive effect on the immune response also reduces the risk of secondary infection. Fatty acid esters have shown to limit the overreaction of the immune system by reducing the level of pro-inflammatory mediators as illustrated in Figure 2. BENEFITS IN PIGLETS: FATTY ACID ESTERS REDUCE THE COLONIZATION OF STREPTOCOCCUS SUIS (SS9) Streptococcus suis is a widespread swine pathogen causing sepsis, meningitis, and other infections, often requiring antibiotics use to control diseases. The upper respiratory tract is believed to be the primary transmission route of S. suis and the gastro-intestinal tract the secondary one. To be able to cause clinical infection S. suis has first to adhere and colonize in the animal and then to translocate through epithelial barrier, spread in connective tissues, lymphatic system and blood stream and to infect different organs. After being transmitted nasally or orally, S. suis can colonize the palatine tonsils of pigs and induce negative effects on animal. To comfort previously CMIs data obtained in vitro toward this pathogen, a trial was conducted to describe effects of a fatty acid esters-supplemented premixture in weaned piglets challenged with serotype 9 (SS9). At weaning, 30 piglets were allocated to 3 groups: unchallenged with control diet, challenged with control diet (positive control), challenged with fatty acid esters supplemented diet (FA-esters). All piglets received an adaptation diet during the first Figure 2. Effects of Fatty acid esters on pro-inflammatory mediators (IL-8 and TNF-α) at different dosages, on cells culture models after bacterial (E. coli) and endotoxins challenges (LPS). The symbols "*" (p ≤ 0.05) and "**" (p ≤ 0.01) indicate significant differences compared to the control.
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