الفهرس 
Prevalence and transmissibility of antimicrobial resistance genes in heat treated milk
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Abstract
This study investigated the persistence and quantification of blaZ, mecC and tetK plasmid-mediated ARGs copy numbers of two staphylococcal strains in both milk and Tris - EDTA (TE) buffer over 3 weeks storage on refrigeration +4oC. During subsequent storage after pasteurization, all tested genes showed increased copy numbers. By electroporation of these genes to the Staphylococcus aureus RN42200 electro-competent strain, both mecC and tetK genes were still expressive and transferable. The formation of VBNC cells was estimated with viability staining and quantitative PCR of 16S rDNA copy numbers of both staphylococcal strains. On the other hand, surveying the prevalence of nine plasmid-mediated and one genomic AMR genes in 100 (50 bulk tank milk & 50 milk filters socks) samples at farm level and 152 (84 pasteurized and 68 ultra-heat-treated milk) commercial samples, results revealed that sul2 gene was the most prevalent plasmid-mediated gene in (96%) milk filters socks, (48%) bulk tank milk, (68%) pasteurized and (43%) UHT samples; on contrary the mecA gene could not be detected in any sample. Moreover, currently practiced commercial pasteurization not only failed to decrease the prevalence of the bla-TEM-B1 (43%), tetK (30%) and tetA (55%) plasmid-mediated AMR genes, but also potentially stimulates dairy microbiota to enter into a viable but non-culturable (VBNC) state. In contrast, after the sterilization treatment all the genes showed decreases in copy numbers, and viability assessment showed that UHT treatment is less to induce VBNC state. Continued research is necessary to identify bacterial species entering the VBNC state after pasteurization, assess their potential resuscitation hazard level, and shed more light on the expression and possibility of horizontal gene transfer of those plasmid-mediated AMR genes to gut microbiota