Evaluation of Susceptibility to Glycopeptides in Oxacillin Resistant Staphylococcus aureus Strains

Abstract

The decrease in susceptibility to glycopeptides by oxacillin resistant Staphylococcus aureus (ORSA) has become a current problem. Objective: To evaluate susceptibility to glycopeptides in ORSA strains isolated in the University Hospital, Maracaibo, during the first quarter of 2010. Methods: Oxacillin resistance of the ORSA strains was verified by diffusion on agar (oxacillin 1 μg and cefoxitin 30 μg, OXOID®), a screening test in Müeller Hinton agar with 6 μg/mL of vancomycin (Sigma®), and E-test® for minimum inhibitory concentration (MIC) for oxacillin, detection of PBP2a (Latex, OXOID®) and the mecA gene by polymerase chain reaction (PCR). In addition, susceptibility to glycopeptides was determined by disk diffusion (teicoplanin, 30 μg OXOID®), MIC by E-test®, screening test in Müeller- Hinton agar with teicoplanin (5 μg/ml) or in brain heart infusion agar with vancomycin (6 μg/mL), glycopeptide hetero-resistance detection by GDR E-test® and detection of the vanA gene using PCR. Results: No ORSA strain was isolated with intermediate resistance (VISA or hVISA), nor with high-level resistance to glycopeptides. Conclusions: Locally, there is no incidence of ORSA strains resistant to glycopeptides; therefore, these antibiotics continue to be useful for treating infections produced by this important pathogen.

Keywords

• SAOR
• glicopéptidos
• resistencia.