Evaluation of multidrug efflux pump expression in clinical isolates of Staphylococcus.aureus

Abstract

BackgroundOne of the mechanisms of Staphylococcus aureus resistance to ciprofloxacin is the presence of efflux pumps. The aim of this study was to determine the frequency and expression of norA, norB and norC efflux pump genes in ciprofloxacin-resistant Staphylococcus aureus clinical isolates. Materials and methodsIn this study, 40 isolates of S. aureus were obtained from blood and urine samples. Antibiotic resistance pattern by disc diffusion method and the minimum inhibitory concentration (MIC) was evaluated. Identification and expression of nor efflux family genes (norA, norB, and norC) in ciprofloxacin-resistant isolates of S. aureus were determined using Real-Time PCR method. ResultsThe resistant to ciprofloxacin, Gentamicin, Cotrimoxazol, Erythromycin and Amoxicillin was 42.5%, 12.5%, 12.5%, 50% and 87.5%, respectively. All of ciprofloxacin-resistant isolates were positive for of norA, norB, and norC genes. The results of Real-Time PCR showed that all ciprofloxacin-resistant isolates are active in the case of efflux pumps. Isolates showed different expressions of the norA, norB and norC genes. Expression levels of norA and norB increased by 6.8 and 7.1 fold, respectively. ConclusionThe results indicated that nor efflux family genes were expressed in all ciprofloxacin-resistant isolates of S. aureus. Moreover, there is an association between the expression of the efflux pump genes and resistance to ciprofloxacin in S. aureus isolates.