Foodborne antibiotics enrich human gut microbiota with pathogens producing extended-spectrum β-lactamases and carbapenemases.

Antimicrobial resistance is a serious global health threat, yet the drivers of its spread among humans are not fully understood. Antibiotics can enter the human gastrointestinal tract through the food chain, leading to the presence of low concentrations in the gut microbiota. However, the role of such traces in promoting the implantation of drug-resistant pathogens in the gut microbiota has never been explored in a controlled experimental setting. Using an in vitro model of the human gut microbiota, we tested whether traces of 19 antibiotics used in both human and veterinary medicine, alone or in combination, lead to the enrichment of Gram-negative pathogens producing extended-spectrum β-lactamases or carbapenemases. Twenty-eight strains of Gram-negative pathogens epidemic in humans (10 Escherichia coli, 6 Klebsiella pneumoniae, 5 Enterobacter hormaechei, 4 Acinetobacter baumannii, 3 Pseudomonas aeruginosa) were tested. We found that antibiotics at levels similar to those measured in the feces of healthy individuals (fluoroquinolones, 1-100 μg L-1; trimethoprim, 100 μg L-1; a mixture of fifteen veterinary antibiotics, 10-20 μg L-1) enriched the human gut microbiota with those resistant pathogens. Overall, the present study indicates that dietary consumption of some antibiotics can result in concentrations in the human colon sufficiently high to favor the implantation of exogenous antibiotic-resistant pathogens. These findings highlight the need to reassess permissible antibiotic concentrations in food and critically evaluate agricultural practices contributing to the contamination of animal- and plant-based products.