Monitoramento de vancomicina em pacientes em tratamento hemodialítico com infecções de corrente sanguínea por Staphylococcus spp.

Abstract

Vancomycin (van) is empirically prescribed for the treatment of staphylococcal infections in patients undergoing hemodialysis (HD). The monitoring of the minimum serum concentration (CSM) of van is used as the most accurate and practical method to estimate its effectiveness, it is recommended that CSM be maintenaided between 10 and 20 mg / mL. The aim of this study was to assess the van CSM achieved in HD patients, during a period of two years and correlate them with the minimum inhibitory concentration (MIC) of this glycopeptide Staphylococcus spp recovered from bacteremia in these same individuals. The recovered samples (N=80) were tested for MIC (broth or agar dilution): vancomycin, gentamycin (gen), oxacillin (oxa), tetracycline (tet), rifampicin (rif), ciprofloxacin (cip), penicillin G (pen) and daptomycin (dap). Serum samples (N=101) were collected from 22 patients treated with1g of vancomycin every 4-5 days plus gentamicin (1.5-2.0 mg/kg) at the end of each HD. The samples were collected before each hemodialysis session, in the 0, 48, 72, 96 and 120 hours after infusion of the drug. The serum constration of van were obtained by chemiluminescent microparticle immunoassay (CMIA). A microbiological assay for van measurement was performed using the pour-plate technique using molten salts minimal agar. S. aureus was the most frequently isolated species (24%), followed by coagulase-negative staphylococci (CoNS) (15%). Higher rates of resistance occurred to oxa (17% and 58%), pen (85% and 84%) and cip (26% and 45%) in S. aures e SCoN, respectively. From the samples, 77,8% had serum concentrations <10 μg/mL and considering only the samples collected immediately before the next van dose (CSM), 90.6% also contained van in concentrations lower than those recommended for effective antistaphylococcal activity. The values of serum concentrations of van obtained by bioassay showed strong correlation with the CMIA (gold standard) (R2 = 0.96), with statistically similar values (p <0.05) when applied to the correction factor. The prevalence of Staphylococcus spp oxacilin resistant supports the empirical use of van, however, there is a high rate of S. aureus isolates which had a van MIC of 1 µg/ml (59.5%) which associated with low Cmim of van to which these patients are submitted indicates a higher probability of treatment failure and selection of resistant strains. An individualized therapeutic approach and monitoring of the drug should be considered. Thus, microbiological assay was validated, because of their lower cost and simplicity of the technique which facilitates the implementation of vancomycin monitoring in routine of small clinical laboratories.