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

SIMPLE SUMMARY: Salmonella enterica subsp. enterica serovar Infantis (S. Infantis) has emerged as a relevant serovar commonly reported in poultry products, which represents a potential public threat. Microalgae synthesize molecules that exert positive effects both on chicken performance and health. Tetraselmis chuii produces fermentable polysaccharides capable of influencing caecal diversity. We tested if the administration of T. chuii could alter caecal microbiota in favor of a reduced S. Infantis load. Animals were fed a microalgae-based diet and challenged with bacteria on day 4. Two days after infection, caecal samples were taken and the viable load of S. Infantis was estimated utilizing a PMAxx(TM)-based qPCR method, which was developed and tested for assessing the differences between groups. Dietary inclusion of the chlorophyte did not alter bacterial viable load; however, the method proved to be efficient, sensitive, and repeatable. Certainly, the approach used herein could be applied in studies evaluating the effects of different treatments on Salmonella caecal colonization. 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 PMAxx(TM)-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.