SUSCEPTIBILITY PROFILE OF Staphylococcus aureus BLOOD ISOLATES AND COMPARISON OF VANCOMYCIN MIC DETERMINATION METHODS

Introduction: The existence of inconsistencies in the vancomycin minimum inhibitory concentration (MIC) for Staphylococcus aureus obtained by automated methods when compared with the results obtained by methods such as Etest ® and broth microdilution (BMD) shows the necessity of evaluate and compare these results. Materials: and Methods: Regarding that, vancomycin MIC, and susceptibility profiles of 62 S. aureus isolates from blood cultures were all determined using the Etest ® , BMD, and Vitek ® 2 methods, these three methods evaluating their susceptibility profiles. Results: and Discussion: Methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) S. aureus strains showed susceptibility to vancomycin, teicoplanin, linezolid, daptomycin and tigecycline. Vitek ® 2 (r = 0.6975, p<0.001) and BMD showed a better correlation between vancomycin MIC compared to Etest ® (r = 0.2563, p<0.00444); however, Vitek ® 2 was overestimated by MIC compared to BMD. Conclusion: Therefore, it is recommended to implement complementary methods to confirm if the high vancomycin MIC results are valid, thereby avoiding inappropriate use of antibiotics and the increase of resistance.