Susceptibility profile of Staphylococcus aureus isolates in blood cultures from a tertiary hospital - comparison of methods for determination of minimum inhibitory concentration of vancomycin

Abstract

Objective: to evaluate the antimicrobial susceptibility profile of Staphylococcus aureus isolates from blood cultures and compare methods for determining
the minimum inhibitory concentration (MIC) of vancomycin. Methods: an observational study conducted in a tertiary hospital, involving 62 clinical isolates of S. aureus. In addition, the MIC of vancomycin was determined using the Etest®, broth microdilution (BMD), and Vitek® automated system methods. Clinically relevant antimicrobial susceptibility profiles were evaluated, and agreement between methods was analyzed by statistical correlation
using IBM-SPSS® software. The study was approved by the hospital's Research Ethics Committee under registration number 5.557.687/2022. Results: methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) isolates were susceptible to vancomycin, teicoplanin, linezolid, daptomycin, and tigecycline. A better correlation was observed between the vancomycin MIC values obtained by Vitek®2 and BMD compared to Etest®. However, Vitek®2 tended to overestimate MIC compared to BMD. Conclusion: the results indicate the importance of using complementary methods to validate high vancomycin MIC values, contributing to more appropriate therapeutic decisions and the prevention of bacterial resistance.