الفهرس 
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Abstract
We clarified the effect of sarA mutation on the antimicrobial resistance and virulence factors of S. aureus. We used UAMS-1 wild type strain, its sarA mutant strain and revertant strain. The bacterial growth rate was measured for the three strains and the results revealed that the growth rate was slightly decreased after sarA mutation. Antimicrobial susceptibility test was carried out. However, no significant difference in the inhibition zone diameter was observed between the three strains. Antimicrobial resistance genes including; fmtA, fmtB, Blaz, msrA, msrB, fusA, norA, tetra, fosB/fosD and chloram were detected successfully within the three strains using PCR. Real time PCR analysis of the previously mentioned genes was accomplished. No significant difference was observed between the expression levels of the tested antimicrobial resistance genes between the three strains. The effect of sarA mutation on virulence factors production and their expression levels was tested. We found a manifesting decrease in biofilm formation in the sarA mutant strain. Moreover, sarA mutation effect on lipase activity revealed an obvious decrease in lipase activity in the sarA mutant strain. Additionally, protease activity was compared. We found a significant increase in protease activity in the sarA mutant strain confronting from the wild type and revertant strains. Also, our data indicated a manifesting decrease in hemolysin activity in the sarA mutant strain. Hence proved that, staphylokinase activity increased notably subsequent to sarA mutation contrasting from the wild type and revertant strains. The agglutination time was measured in the three strains and it was found that sarA mutation caused a considerable decrease in the agglutination time. Hyaluronidase activity increased after sarA mutation. Lecithinase activity was measured in wild type, sarA mutant and revertant strains. It decreased notably after sarA mutation. Finally, coagulase activity was measured and showed a significant increase in the coagulation time in the sarA mutant strain contrasting from the other two other strains, the wild type and revertant. S. aureus virulence genes were detected successfully using PCR. The detected genes in our study were plc, atl, nuc, sea, efb, hlgC, hlgB, hlgA, hla, hlb, lukF, lukS, hld, sak, coa, sspA, sspB, scp, aur, hysA1, hysA2, lip1, lip2, lecithinase, sbi and isaA. They were detected in the three strains. Also, the levels of expression of previously mentioned virulence factors genes were measured using real time PCR. Expression level of plc gene increased strongly in the mutant strain contrasting from the wild type and revertant strains. The level of expression of nuc and atl was raised manifestly upon sarA mutation. Also, level of expression of sak increased in the mutant strain. Besides, the expression levels of protease encoding genes including aur, sspA, sspB and scpA showed an obvious increasing in sarA mutant strain. Moreover, hysA1 and hysA expression levels increased upon sarA mutation. Otherwise, efb showed significant decrease in the expression level in the sarA mutant strain. Also, hla, hlb, hlgA, hlgB, hlgC and hld expression level was lowered after sarA mutation. In addition, coa level of expression was reduced after sarA mutation. Additionally, lukS-PV and lukF-PV level of expression was lessened in the sarA mutant type. Furthermore, geh1and geh2 levels of expression were minimized in the mutant strain. Expression level of lec was found to be reduced in the sarA mutant strain. Finally, sbi and isaA expression levels were found to be dropped in the sarA mutant strain.