Methicillin resistant and susceptible Staphylococcus aureus: Appraising therapeutic approaches in the Northwest of Iran

Staphylococcus aureus is a versatile organism causing mild to life threatening infections. The major threat of this organism is its multidrug resistance. The present study was carried out to investigate in - vitro activity of conventional antibiotics routinely prescribed for methicillin resistant S. aureus (MRSA) and methicillin sensitive S. aureus (MSSA) infections in the Northwest of Iran and other alternating therapeutic agents which are recommended for Gram positive organisms. Clinical isolates of S. aureus were subjected to multiplex PCR for simultaneous speciation and detection of methicillin resistance. Antibacterial susceptibility pattern was determined using disk diffusion. The Minimum Inhibitory Concentrations (MICs) were determined using E-test strips. The results revealed presence of nuc gene in all S. aureus isolates detected phenotypically earlier whereas, mecA gene was observed in 54% of strains. On disk diffusion and MIC determination assay, all MRSA and MSSA strains were susceptible to mupirocin (except one MRSA strain), linezolid and teicoplanin. Six vancomycin intermediate S. aureus strains were detected (VISA) with MIC = 4 μg/mL, 5 of them being MRSA. In disk diffusion assay, 17.3% and 3.7% of isolates showed resistance to rifampin and fusidic acid, respectively. However, MIC50 and MIC90 tests shows promising in – vitro impact. In – vitro mupirocin was found as an effective prophylactic ointment for nasal S. aureus eradication. Our data emphasize the performance of surveillance exercises to outline the existing antibiotics prescription policies and to slow down the emergence of multidrug resistant strains.