Determination of Incidence of Resistance to Oxacillin, Vancomycin, Rifampin, Linezolid and Fusidic Acid in Staphylococci Obtained From Various Culture Specimens

Studies Over the last decade, methicillin-resistant Staphylococcus aureus (MRSA) strains have become endemic in hospitals worldwide. Emergence of multi-drug resistant S. aureus significantly differs between health centers. Therefore, the present study aimed at determining the incidence of resistance to oxacillin, vancomycin, rifampin, linezolid and fusidic acid in Staphylococci obtained from various culture specimens. In an analytic-descriptive cross-sectional study, 150 specimens obtained from hospitalized patients in Tabriz Sina and Imam Khomeini Hospitals with positive result for S. aureus were evaluated. Resistance to oxacillin, vancomycin, rifampin, linezolid and fusidic acid was determined by disk diffusion method. The minimum inhibitory concentration (MIC) was also determined by E-test stripes. The resistance rate of S. aureus to oxacillin, rifampin and fusidic acid was 54%, 10.7% and 1.3%, respectively. There was no case with resistance to linezolid. Resistance to vancomycin was intermediate in 5 (3.3%) isolates. In 2.7% of the cases, there was simultaneous resistance to vancomycin (intermediate) and oxacillin which were susceptible to rifampin. The rate of resistant isolates to oxacillin was more in specimens obtained from wound, blood, tracheal tube and secretions of nasopharynx comparing with the sensitive cases. The rate of resistant isolates to rifampin was more in specimens obtained from wound and tracheal tube comparing with the sensitive cases. The resistance rate to oxacillin and rifampin has been elevated among S. aureus comparing with the previous reports. There is a good coverage between oxacillin or vancomycin and rifampin.