Introducrtion:Introduction: Fluoroquinolones are among useful antibiotics against infections caused by Staphylococcus aureus, but today resistance to these classes of antibiotics is a serious problem in patient’s treatments. Overexpression of norA gene is a Fluoroquinolone resistance mechanism in Staphylococcus aureus to be studied through our investigation.
 
Materials & Methods: In this study, 50 Staphylococcus aureus strains were isolated from nasal infection in Sanandaj town. These strains were then identified by conventional biochemical tests. Disk diffusion testing for antibiotic resistance assessment and PCR for existence of norA gene were done. Then, PCR products were sent to Bioneer Company for sequential testing. As a result, nucleotides and amino acid mutations were studied, based on sequencing results and Expasy translator.
 
Findings: The results of biochemical tests were as coagulase, mannitol fermentation, DNase and hemolysis positive, novobiocin sensitive and polymyxin resistance. Oxacillin (42%), erythromycin (46%), doxycyclin (10%), amikacin (20%), tetracycline (24%), penicillin (68%), ciprofloxacin (10%), vancomycin (6%), nalidixic acid (70%) were the antibiotics to which resistance rate was assessed. All the resistance strains had norA gene and 4 identical points of mutation were identified as, G491->A, C537-> T, C593-> C and A585->G respectively. Then, after translation in D315 base, aspartic acid (D) had been converted into Glycine (G).


Discussion & Conclusion:  According to our results, common nucleotide and amino acid mutations were observed in four strains of ciprofloxacin resistant Staphylococcus aureus. Therefore, more studies are needed to find out if the mentioned mutation is the cause of overexpression of norA.