Background: Coagulase-negative staphylococci (CNS) are a common cause of nosocomial infections. In recent years, an increase in the incidence of methicillin-resistant coagulase-negative staphylococci (MRCNS) has led to the severity of the disease.
Objectives: The aim of this study was to isolate and identify MRCNS strains by oxacillin disk agar diffusion, oxacillin agar screening, and polymerase chain reaction (PCR) and to evaluate their antibacterial resistance patterns.
Patients and methods: Totally, 122 CNS isolates were collected from the clinical specimens of four hospitals in Iran. Susceptibility testing was performed by disk agar diffusion against 15 antimicrobial agents. Then, disk agar diffusion, agar screening, and PCR were applied to determine susceptibility to oxacillin.
Results: Out of the 122 isolates, 92 isolates were found to be MRCNS by PCR. The sensitivities and specificities of disk agar diffusion and agar screening were 89.2% and 69% and 93.8% and 96.3%, respectively. Also, 93 CNS isolates were resistant to Methicillin according to disk agar diffusion.
Discussion: Our results indicated that agar screening was superior to oxacillin disk agar diffusion. A comparison between the antibiotic sensitivity patterns of the MRCNS and the Methicillin-Susceptible Coagulase-Negative Staphylococci (MSCNS) showed that the MRCNS were predominantly multiple-drug resistant isolates as the simultaneous resistance rate to 4 or more antibiotics in the MRCNS and MSCNS was 93% and 56%, respectively.
Keywords: Coagulase; Methicillin Resistance; Staphyloccus.