Molecular Characterization of Tetracycline-Resistant Genes in Staphylococcus aureus Isolated from Dairy Cows and She-camels Suffering from Subclinical Mastitis

The administration and the mass use of antimicrobial therapy without the appropriate dose or exposure time, enhance the emergence of antimicrobial resistance leading to increasing the difficulty to control the infectious bacterial agents in dairy farms and hence impose negative economic impact on dairy industry. Tetracycline resistance represented with several genes in the bacterial chromosome, but this study was concerned with two genes, tet (k) and tet (38). The tet (38) gene had high prevalence than the tet (k) gene and one of the interesting features found in this work that the tet (k) was found only in most of MRSA isolates (mecA gene harboring) while the tet (38) gene was found in all S. aureus isolates (MRSA and MSSA). High level of similarities were found between these genes isolated from different stains and their corresponding reference sequences retrieved from the GeneBank by applying the multiple sequence alignment and the phylogenetic analysis. Further analysis would be done to determine other genes of resistance to explore the whole picture of antibiotic resistance but on the genetic level.