Citywide metagenomic surveillance of food centres reveals local microbial signatures and antibiotic resistance gene enrichment.

The distribution of microorganisms in built environments with high human traffic, such as food centres, can potentially have a significant impact on public health, particularly in the context of increasing worldwide incidence of food and fomite-related outbreaks. In many major Asian cities, public food centres are central to daily food consumption, yet there is a lack of baseline knowledge about their environmental microbiomes. We performed a city-wide metagenomic survey of food-centre microbiomes in Singapore, covering 16 centres and 240 samples, to map the abundances of microbial (bacteria, archaea, fungi, viruses) and non-microbial DNA across two timepoints. Food-centre microbiomes were found to be enriched in food-related DNA signatures compared to other environments, such as hospitals and offices, with specific food-microbe associations (e.g., Enterobacteriaceae and fish) and food DNA providing a partial explanation for the microbial profiles observed (44% of variation explained). Machine learning analysis identified a small set of microbial species (n = 22) that serve as highly accurate (>80%) location-specific signatures for various food centres, some of which persist even after 3 years. Profiling of antibiotic resistance genes (ARGs) and pathogens identified a surprising enrichment of ARGs in food centres relative to other non-healthcare environments (>2.5×), and an order of magnitude enrichment of key pathogenic species (e.g., Klebsiella pneumoniae, Enterobacter spp) even compared to hospital environments. These results highlight the contribution of diverse biotic and abiotic factors in shaping the unique microbiome profiles of different food-centre environments, and the potential for using metagenomic surveillance to understand the risk for infections and antibiotic resistance gene transmission.