Evaluation of norB gene expression in ciprofloxacin resistant Staphylococcus aureus strains

Today, antibiotic resistance of staphylococcal infection has become a major problem both in hospitals and in the community. The aim of this study is to investigate the expression level of norB gene in quinolone-resistant Staphylococcus aureus isolated from clinical samples in Qom city. Staphylococcus aureus isolates were obtained from different clinical samples by standard biochemical and culture methods. In the following, the presence of femA genes as a molecular diagnosis of Staphylococcus aureus, norB as a target gene and rpoD as a reference gene were investigated using Multiplex PCR technique. The pattern of antibiotic resistance was determined using the standard disk diffusion method and the minimum inhibitory concentration of the ciprofloxacin antibiotic of the isolated strains was determined by the microdilution method. The expression level of norB gene was determined using Real-Time PCR method. A total of 82 isolates were obtained from 240 clinical samples using standard biochimical and culture methods. Multiplex PCR technique had shown that genes femA, norB, rpoD are simultaneously present in 40 isolates (48/78%). Also, after analyzing the antibiotic pattern, 26 strains were resistant to ciprofloxacin. The results of the Real-Time PCR technique indicated an increase in norB gene expression among ciprofloxacin resistant strains. According to the results obtained, the norB efflux pump plays an essential role in creating resistance to ciprofloxacin, and investigating the presence of this gene can be important in suggesting a treatment model.