Sensitivity to vancomycin of oxacilin tolerant clinicai strains of Staphylococcus aureus

Abstract

Twenty oxacillin tolerant strains of Staphylococcus aureus, identified among 80 clinica/ isolates from patients admitted to the Hospital Universitário Antônio Pedro (HUAP), had their susceptibilities tested to vancomycin through minimal inhibitory concentrations (M/Cs) and minimal bactericida/ concentratíons (MBCs) determined by the two-fold dilutlon technique. None of the strains exhibited either tolerance (MBCIMIC> 16) or resistance to vancomycin. M/Cs and MBCs found for oxacillin showed that, in spite of the tolerance to this penicillin, only 5 strains (6.25 % ) could not be treated with this beta-lactam, since those strains exhibited MBCs > 25 μgim/, with M/Cs ôetween 0.39 and 6.25 μgim/. Onthe other hand, MBCs for vancomycin ranged from 0.39 to 12.50 μgim/), and so, this glycopeptide can be usedto fight those oxacillin tolerant strains with MBCs < to the maximum sistemic concentration .reached by vancomycin.