A carvacrol-based product reduces Campylobacter jejuni load and alters microbiota composition in the caeca of chickens.

AIM: This study was conducted to test the ability of a carvacrol-based formulation (Phodé, France) to decrease the C. jejuni caecal load in inoculated broiler chickens and to study the impact of the C. jejuni inoculation alone or combined with the product, on the caecal microbiota. METHODS AND RESULTS: On day 1, chickens were either fed a control feed or the same diet supplemented with a carvacrol-based product. On day 21, the carvacrol-supplemented chickens and half of the non-supplemented chickens were inoculated with C. jejuni (108  CFU). Quantitative PCR was used to quantify C. jejuni in chicken caecal samples and 16S rRNA gene sequencing was carried out at 25, 31 and 35 days of age. A significant decrease of 1.4 log of the C. jejuni caecal load was observed in 35-day-old chickens supplemented with the product, compared to the inoculated and unsupplemented group (p < 0.05). The inoculation with C. jejuni significantly increased the population richness, Shannon and Simpson diversity and altered beta-diversity. Compared to the control group, the C. jejuni inoculation causes significant changes in the microbiota. The carvacrol-based product associated with C. jejuni inoculation increased the diversity and strongly modified the structure of the microbial community. Functional analysis by 16S rRNA gene-based predictions further revealed that the product up-regulated the pathways involved in the antimicrobial synthesis, which could explain its shaping effect on the caecal microbiota. CONCLUSIONS: Our study confirmed the impairment of the caecal bacterial community after inoculation and demonstrated the ability of the product to reduce the C. jejuni load in chickens. Further investigations are needed to better understand the mode of action of this product to promote the installation of a beneficial microbiota to its host. SIGNIFICANCE AND IMPACT OF THE STUDY: Results suggested that this product could be promising to control C. jejuni contamination of broilers.

Monoterpenoid-based preparations in beehives affect learning, memory, and gene expression in the bee brain.

Bees are exposed in their environment to contaminants that can weaken the colony and contribute to bee declines. Monoterpenoid-based preparations can be introduced into hives to control the parasitic mite Varroa destructor. The long-term effects of monoterpenoids are poorly investigated. Olfactory conditioning of the proboscis extension reflex (PER) has been used to evaluate the impact of stressors on cognitive functions of the honeybee such as learning and memory. The authors tested the PER to odorants on bees after exposure to monoterpenoids in hives. Octopamine receptors, transient receptor potential-like (TRPL), and γ-aminobutyric acid channels are thought to play a critical role in the memory of food experience. Gene expression levels of Amoa1, Rdl, and trpl were evaluated in parallel in the bee brain because these genes code for the cellular targets of monoterpenoids and some pesticides and neural circuits of memory require their expression. The miticide impaired the PER to odors in the 3 wk following treatment. Short-term and long-term olfactory memories were improved months after introduction of the monoterpenoids into the beehives. Chronic exposure to the miticide had significant effects on Amoa1, Rdl, and trpl gene expressions and modified seasonal changes in the expression of these genes in the brain. The decrease of expression of these genes in winter could partly explain the improvement of memory. The present study has led to new insights into alternative treatments, especially on their effects on memory and expression of selected genes involved in this cognitive function. Environ Toxicol Chem 2017;36:337-345. © 2016 SETAC.