Abstract

IDENTIFICATION OF AN EFFLUX PUMP GENE, NORA, IN METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS IN BAGHDAD

Mohammed F. AL-Marjani*, Ahlam K. Abdal and Dawood Salim Edan

Abstract

A total of 75 clinical isolates of Methicillin-resistant Staphylococcus aureus(MRSA) were collected from various infections from different hospitals in Baghdad. The susceptibility to different antibiotics was evaluated by disk diffusion method. Results showed that all isolates were resistant to ceftriaxone, cloxacillin and aztreonam. The resistance to ciprofloxacin and norfloxacin were 17.33 % and 20% respectively. The minimum inhibitory concentrations (MICs) for ciprofloxacin and norfloxacin ranged from 4 to 1024 μg/ml for both Antimicrobial agents. Ciprofloxacin resistant isolates were tested for efflux pumps by using Ethidium Bromide-Agar Cartweel Methode (EtBrCW), the results showed that 52.9% of isolates give positive result. Polymerase Chain Reaction (PCR) technique was performed done using specific primer targeting the specific sequences of the norA gene, The results showed that norA found in 47% of isolates. Nucleotide sequence for norA gene in 9 isolates were determined , results revealed consistency reaching up to 90 % as compared Nitrogen bases sequence of the norA gene present in the Staphylococcus aureus strain in NCBI . Detection of gene expression was performed done by using q RT-PCR technique after RNA extraction and cDNA syenthesis, the result showed that gene expression were various among isolates, and the gene expression increase with increasing MIC of ciprofloxacin and norfloxacin. The effect of biosurfactant (from Lactobacillus rhamnosus ) as efflux pumps inhibitors was tested by detection of MIC for ciprofloxacin alone and mixed with biosurfactant , the result showed ability of biosurfactant in decreasing the MIC to two or four-fold in the presence of inhibitor. This refer to biosurfactant effective material against NorA efflux pump.

Keywords: Methicillin-resistant S. aureus (MRSA), efflux pumps, NorA gene.