A PMAxxTM qPCR Assay Reveals That Dietary Administration of the Microalgae Tetraselmis chuii Does Not Affect Salmonella Infantis Caecal Content in Early-Treated Broiler Chickens

Abstract

Salmonella enterica serovars cause infections in humans. S. enterica subsp. enterica serovar Infantis is considered relevant and is commonly reported in poultry products. Evaluating innovative approaches for resisting colonization in animals could contribute to the goal of reducing potential human infections. Microalgae represent a source of molecules associated with performance and health improvement in chickens. Tetraselmis chuii synthesizes fermentable polysaccharides as part of their cell wall content; these sugars are known for influencing caecal bacterial diversity. We hypothesized if its dietary administration could exert a positive effect on caecal microbiota in favor of a reduced S. Infantis load. A total of 72 one-day-old broiler chickens (COBB 500) were randomly allocated into three groups: a control, a group infected with bacteria (day 4), and a group challenged with S. Infantis but fed a microalgae-based diet. Caecal samples (n = 8) were collected two days post-infection. A PMAxxTM-based qPCR approach was developed to assess differences regarding bacterial viable load between groups. The inclusion of the microalga did not modify S. Infantis content, although the assay proved to be efficient, sensitive, and repeatable. The utilized scheme could serve as a foundation for developing novel PCR-based methodologies for estimating Salmonella colonization.

Effects of Lactobacillus fermentum Administration on Intestinal Morphometry and Antibody Serum Levels in Salmonella-Infantis-Challenged Chickens

“…Chickens were assigned at random into four experimental groups: (I) the control group, in which a saline solution (0.2 mL) was applied individually to birds each time their counterparts were inoculated; (II) the L. fermentum group, in which birds were treated with a suspension of the probiotic (10 9 colony-forming units [CFU]/0.2 mL) that was applied from days 1 to day 7 of the experimental period [ 26 ]; (III) the S . Infantis group, infected with a suspension of the bacteria (10 7 CFU/0.1 mL) on day 4 [ 14 , 19 ]; and finally, in group IV, animals were exposed to the probiotic during the first week and inoculated with S . Infantis on the fourth day.…”

“…Bacterial strains were administered orally ( Table S1 ); they were prepared as described previously [ 14 , 26 ]. The L. fermentum strain CCM7514 was provided in a lyophilized form by the Czech Collection of Microorganisms (CCM), Brno, Czechia; the strain originated from the intestine of domestic chickens.…”

“…The solution was arranged in series using plate count agar, and adjusted at around 1–2 × 10 7 CFU/0.1 mL. Each bird was inoculated orally with 10 7 CFU/0.1 mL on the fourth day of the experiment [ 14 ].…”

“…On the other hand, dietary administration of the green microalga Tetraselmis chuii did not alter S . Infantis cecal load in broilers, despite the presence of fermentable polysaccharides as part of the cell wall [ 14 ]. Such polysaccharides are known for modulating cecal microbiota [ 15 ], and it has been shown that application of seaweed-derived polysaccharides reduced S .…”