Análise de mecanismos de resistência a polimixina em isolados de Klebsiella pneumoniae

Abstract

Infections for Klebsiella pneumoniae Carbapenemase-producing have been a public health problem leading to increased patient morbidity and mortality, which has led to the reintroduction of a previously discontinued antimicrobial for human use, polymyxins. The raise in resistance to polymyxins has made treatment even more difficult, which is worrying due to the high worldwide dissemination of these strains.This study aimed to perform a genetic analysis of two-component systems involved in polymyxin resistance in Klebsiella pneumoniae isolates. Sixteen multiresistant K. pneumoniae isolates were studied. The clonal relationship was performed from the investigation of repeated extragenic palindromic sequences (REP). The genes of the two-component enzyme regulatory systems (pmrA, pmrB, phoP, phoQ) were amplified by polymerase chain reaction (PCR). The identification of mutations was performed by DNA sequencing with comparative analysis using the MGH 78578 strain as reference. It was possible to distinguish the presence of four groups with clonal relationship of the same species with a variation of 2 to 5 unshared bands, indicating a pattern of similarity between all bacteria in the study. All isolates had more than one mutation in the coding regions of the genes studied, the prevalence was of mutations classified as silent in pmrA and phoP. However, Frameshift Nonsense and Missense mutations were identified in pmrB and phoQ genes, which led to alterations in the amino acid chain and production of a non-functional protein. Nucleotide alterations in the coding regions of the TCS regulatory genes (phoPQ and pmrAB) and the compromise of the protein sequence are considered the most relevant mechanisms regarding the mediation of resistance to polymyxins.