Microbial metabolism affects the antibiotic resistome in the intestine of laying hens.

Intestinal microbial metabolism has an important impact on the health of laying hens, and microbes are also important hosts for ARGs. However, the relationship between intestinal microbes and antibiotic resistance in laying hens is unclear. In this study, a slaughtering experiment, an in vitro fermentation experiment and a single-bacteria culture experiment were carried out, and metagenomic and metabolomic analyses were used to investigate the relationships between microbial metabolism and the antibiotic resistome in the cecum of laying hens. The results showed that there were different types of ARGs in the intestines of laying hens, and the risk scores of the ARGs tended to decrease with growth stage. A total of 1142 metagenome-assembled genomes (MAGs) were obtained, and Escherichia coli was found to be the dominant ARG host, carrying 62 ARGs. Metabolomics revealed that indole and its derivatives, such as indole-3-lactic acid, were negatively correlated with a variety of ARGs. Moreover, in vitro fermentation experiment and single-bacteria culture experiment demonstrated that indole-3-lactic acid reduced the abundance and risk of multiple ARGs in the intestine and inhibited the growth of the ARG host Escherichia coli. In the context of high concern about intestinal microbial metabolism and antibiotic resistance, this is the first study to focus on the relationship between intestinal microbial metabolism and antibiotic resistance in laying hens. These findings have important implications for healthy farming and antibiotic resistance control.