Veterinary session

One of the most fundamental societal needs of the 21st century is adequate food safety, which is now inextricably linked to the mapping of animal and human hazards. One such risk factor is the defining global problem of the 21st century, the potential spread of antimicrobial resistance and its underlying resistance genes through food.

Consumer demand for raw milk and raw dairy products derived from raw milk has increased significantly, despite the health risks, due to their positive impact on nutritional composition and taste. Although many benefits of consuming raw products have been described, it should not be overlooked that the consumption of raw milk and dairy products poses serious health risks as they can be an excellent source of transmissible bacterial, viral, and protozoal diseases, which may also carry antimicrobial resistance genes. In our research, we aimed to track the antimicrobial resistance gene pool changes in raw milk and raw milk products from a small dairy farm through milk processing ("from field to table") to the consumer, using next-generation sequencing.

In each of our studies, we tested the resistance gene pool of the samples, as well as their phage or plasmid carriage and potential mobility, following five parallel sampling runs. In total, we identified about 112 antimicrobial resistance genes. We observed a significant reduction in the resistance gene pool of raw cheese compared to raw milk samples. Still, after one month of ripening, significant enrichment was observed, exceeding the initial gene frequency. Of particular concern, we also identified extended-spectrum beta-lactamase (ESBL) genes in the samples, such as the OXA-662 gene (100% coverage, 99.3% identity) and the OXA-309 gene (97.1% coverage, 96.2% identity). We observed that there was a gene that appeared in the product only after one month of maturation (sul1), indicating contamination. In all samples, the genes regulating the function of the efflux pumps against fluoroquinolones were the most frequent.

In conclusion, the validity of our study is supported by the variation in the gene pool observed during the product pathway and the potential for horizontal gene transfer through the raw products. Of particular concern is the presence of ESBL genes. A new approach and food safety investigation using next-generation sequencing should be considered.