Abstract
The global threat of the “antimicrobial resistance apocalypse” that has arisen in recent years has driven the use of high-throughput sequencing techniques to monitor the profile of resistance genes in microbial populations. The human oral cavity contains a poorly explored reservoir of these genes, and little is known about their abundance and diversity, or how their profile compares with antimicrobial resistance genes in the gut. Here we analyse the resistome profiles of 790 oral cavities worldwide and compare these profiles with paired stool samples from shotgun metagenomic data. We find country-specific differences in the prevalence of antimicrobial resistance gene classes and mechanisms in oral and stool samples. Countries with a higher prevalence of resistance to antibiotic classes relative to their use, contain genes resistant to those classes that co-localise with bacteriophages, suggesting the occurrence of horizontal gene transfer of these genes. Between individuals, the oral cavity contains a significantly higher abundance, but lower diversity of antimicrobial resistance genes compared to the gut, which is likely influenced by differences in microbial hosts and mobile genetic element associations. This is the first study to date that characterises the oral cavity resistome worldwide, identifying its distinctive signatures compared to the gut, and its role in the maintenance of antimicrobial resistance.