Raw milk for human consumption may carry antimicrobial resistance genes

Background: The increasing prevalence of antimicrobial resistance (AMR) is a significant threat to global health. The widespread use of antibiotics is increasingly shortening the time it takes for resistant strains to develop and more and more multi-drug-resistant bacterial strains cause life-threatening infections and death of tens of thousands of people each year. Beyond disease control animals are often given antibiotics for growth promotion or increased feed efficiency, which further increase the chance of the development of multi-resistant strains. By eating of animal products, these strains may meet with human bacteriota. By horizontal gene transfer, the antimicrobial resistance genes (ARG) can be shared among the food and human bacteriota. This study aims to test the presence of antimicrobial resistance genes in milk metagenome, investigate their genetic position and their linkage to mobile genetic elements. Results: We have analyzed raw milk samples that were sold for human consumption at public markets. The milk samples contained genetic material from various bacterial species and the detailed analysis uncovered the presence of several antimicrobial resistance genes The samples contained complete ARGs influencing the effectiveness of acridine dye, cephalosporin, cephamycin, fluoroquinolone, penam, peptide antibiotics and tetracycline. One of ARGs, PC1 beta-lactamase may also be a mobile element that raises the possibility of the transfer of the resistant gene into other bacteria, e.g. to the ones living in the human gut. Conclusion: Our findings raise the opportunity of antimicrobial resistance acquisition of human pathogens not just by antibiotics residual, but by the antimicrobial resistance gene content of animal products.