Antimicrobials have become one of the foundations of modern medicine, yet the rapid spread of resistance threatens their effectiveness. Lactic acid bacteria (MKB) and bifidobacteria were recognised as a reservoir of resistance, but the actual risk posed by strains intentionally introduced into the agro-food chain (SZPK) has not yet been assessed. The aim of our study was to clarify whether these strains present a risk in terms of resistance. Four groups of MKB and bifidobacteria were included in the analyses ̶ in addition to strains from starter cultures or dietary supplements with live bacteria (probiotics), isolates from human milk or colostrum, intestinal mucosa or faeces, and fermented products. Phenotypic susceptibility was determined for 474 strains by microdilution and was most common in intestinal isolates. Antimicrobial resistance genes (ARG) and mobile genetic elements (MGE) were characterised in whole genomes of 1114 strains using comparative genomics. The results revealed that 13.8 % of the strains in the SZPK group contained acquired ARG, most frequently for tetracycline, however, mutations were also common. 75.5 % of acquired ARG were associated with MGE, whose potential for in vivo transmissibility was evaluated by examining metagenomic sequences. We confirmed that ARG and MGE were not as common in the SZPK group as in strains from human intestinal mucosa/faeces, suggesting that this group does not pose a significant threat. However, attention should be paid especially to individual probiotic strains that contain elements that have been shown to have high potential for transferability in the gut microbiota. These elements were uncommon in isolates of natural microbiota from fermented products and were atypical of starter cultures.
|
