Avaliação fenotípica e genotípica de Staphylococcus aureus isolados de pacientes sob tratamento dialítico e transplantados renais : estudo de associação com marcadores genéticos (HLA)

Abstract

Staphylococcus aureus is a pathogen involved in the etiology of nosocomial and community-acquired infections. Healthy individuals can lodge S. aureus in the nasopharynx, and body surface, since the majority of invasive infections caused by this bacterium is endogenous. The disease severity depends on the resistance profile in the face of the antimicrobials usually used in the clinical practice. Kidney transplant patients and on dialysis are risk factors for colonization or infection by S. aureus multi-resistant. The infection is directly related to the individual's immunity and the Major Histocompatibility Complex (MHC) is involved in such functions. In humans, such molecules are known as Human Leukocyte Antigens, or HLA, from the English Human Leukocyte Antigens. It has been shown that different HLA specificities can be more frequent in individuals with certain diseases, however not much is known about the correlation between HLA typing and S. aureus nasal carriage. The present study had as objective to identify the prevalence, genotypic and phenotypic profile of S. aureus samples isolated from nasal vestibules of patients on dialysis and kidney transplant, as well to verify association between MHC molecules and the condition of nasal carriage. The population of this research was consisting of 111 patients on dialysis and 48 kidney transplant. The samples were subjected to Gram Reaction and Tube Coagulase Test. The antimicrobial susceptibility was evaluated by disc diffusion method and test of determination of the minimum inhibitory concentration (MIC). The DNA was extracted with CTAB and the technique of Polymerase Chain Reaction (PCR) was applied for genetic typing with oligonucleotide RW3A and identification of the mecA gene of resistant samples to oxacillin. For HLA typing was used the kit LABType® SSO One Lambda allied to Luminex technology. Among the 48 kidney transplant patients, 75% presented positivity for S. aureus in their nasal vestibules, whereas among the 111 on dialysis, 49% were carriers. From the samples, 10 were resistant to oxacillin and 8 presented the mecA gene, all were sensitive to vancomycin and resistant to penicillin. The others samples also showed high resistance rate to other antimicrobials. There was disagreement between the results of resistance of oxacillin between the Agar dilution method (11%) and disc diffusion (8.7%). The results of genetic typing showed a more homogeneous profile between isolates samples from dialysis' patients than between kidney transplant patients. In relation to HLA typing and association with S. aureus nasal carriage, regardless of the patient group, it was noticed a higher frequency of HLA allele class I (A*03, A*68 and B*15) as suggestive of protection in S. aureus nasal carriage; for HLA molecules class II, the allele DRB1*03 seems to be related, as a genetic marker of susceptibility to the carriage of the bacterium.