TDK conference 2020

Antimicrobial resistance (AMR) of pathogenic bacteria is public- and animal health issue with an increasing significance. Multi-resistant bacteria cause more and more life-threatening infections, and deaths, while the number of constantly effective antimicrobial compounds keeps decreasing.

Though antibiotics used in animal and human healthcare unequivocally play a role in the tendency as a means of selective pressure, some other factors are also inevitable for the inconvenient outcome. Antimicrobial resistance genes (ARGs) themselves are the core components that AMR spreads with among bacterial populations. Thus, the discovery of the physical meeting points where bacteria can execute horizontal gene transfer (HGT) is a biomedical question of indisputable significance.

Unprocessed products, such as raw milk, deriving from animal farms often contain bacteria harbouring ARGs. These ARGs encode resistance against antibiotics used at the farms that are often homologous to the ones at human healthcare systems. Without heat treatment, bacteria are not hindered from multiplication, thus the resistome (total ARG content) of the sample also grows.

In order to gain a more in-detail insight into the possible significance of raw milk in the spread of AMR, the metagenomic analysis of next-generation sequencing (NGS) data of two milk samples accessible at public markets was executed. Besides identifying the taxonomic composition, we examined the resistome and the mobility potential of ARGs in both samples. The core bacteriom consisted of 10 bacterial classes that carried antimicrobial resistance genes detected in outstanding quality against 22 antibiotic groups. 3 ARGs originated from highly mobile plasmids, out of which one, blaZ, that affects the efficiency of ß-lactams, had a phage integrase gene either in its sequential surroundings.

As the heat treatment of raw milk is upon the decision of consumers, in case of its absence bacteriota containing an expanded resistome accesses the gut where the opportunity of an encounter with the host bacteria is facilitated. Such a proximity of the bacterial populations may enable HGT.

Even though, further examinations would be needed to understand the practical significance of our results, this case-study serves as a suggestive example of the potential of modern bioinformatic methods in AMR research. Moreover, it sheds light on the possible role of food in the spread of AMR from a different perspective than examination of remains of antibiotic residuals.