| Summary: | The existence of antibiotic-resistant bacteria in food products, particularly those carrying acquired resistance genes, has increased concerns about the transmission of these genes from beneficial microbes to human pathogens. In this study, we evaluated the antibiotic resistance-susceptibility patterns of 16 antibiotics in eight <i>S. thermophilus</i> strains, whose genome sequence is available, using phenotypic and genomic approaches. The minimal inhibitory concentration values collected revealed intermediate resistance to aminoglycosides, whereas susceptibility was detected for different classes of β-lactams, quinolones, glycopeptide, macrolides, and sulfonamides in all strains. A high tetracycline resistance level has been detected in strain M17PTZA496, whose genome analysis indicated the presence of the <i>tet</i>(S) gene and the multidrug and toxic compound extrusion (MATE) family efflux pump. Moreover, an in-depth genomic analysis revealed genomic islands and an integrative and mobilizable element (IME) in the proximity of the gene <i>tet</i>(S). However, despite the presence of a prophage, genomic islands, and IME, no horizontal gene transfer was detected to <i>Lactobacillus delbrueckii</i> subsp. <i>lactis</i> DSM 20355 and <i>Lactobacillus</i><i>rhamnosus</i> GG during 24 h of skim milk fermentation, 2 weeks of refrigerated storage, and 4 h of simulated gastrointestinal transit.
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