Caracterização de fatores de patogenicidade em amostras de Acinetobacter baumannii obtidas de um hospital universitário em Belo Horizonte, Minas Gerais

Abstract

In recent years, A. baumannii has become a microorganism of great clinical and epidemiological relevant. This importance is due to its extraordinary ability to present resistance, both intrinsic and acquired, to several antimicrobials, besides its ability to survive on the environmental surfaces for long time. Moreover, the pathogenic ability of this specie including invasion, colonization and tissue destruction results from multiple virulence factors produced by this microorganism. The objective of this study was to evaluate virulence factors present in this species, through phenotypic and genotypic analyzes. Twenty-nine samples of antimicrobial multiresistant A. baumannii obtained from patients with various infections admitted to a teaching hospital in Belo Horizonte from 2012 to may 2013 were included, in addition to the reference sample, A. baumannii ATCC 19606. The presence of capsule-associated genes, biofilm, apoptosis and quorum sensing were investigated by the polymerase chain reaction (PCR) technique. For the apoptosis, phagocytosis and reactive oxygen species (ROS) assay, specific kits and flow cytometric analyzes were used. The evaluation of oxidative stress was carried out by the disc diffusion method with hydrogen peroxide. The hemolysis test was performed on 06 different blood types (human, sheep and horse), being those of human origin of factor Rh positive. All samples were positive for gaiU and 76% for wzc. Concerning quorum sensing, 10% of the samples had the luxI gene and 7% luxR. All samples were positive for bap, related to biofilm formation. Regarding OMPs, 14% were positive for omp33 and 31% for ompA. 24% of the samples presented all virulence related genes. In ROS and phagocytosis production assays in flow cytometry, except for one sample, all induced the formation of ROS by macrophages at different rates. In phagocytosis, all samples were phagocytosed, but at different rates. In the induction of apoptosis in macrophages by A. baumannii lines, there were 08 samples which incubation resulted in a significant reduction in the number of macrophages in relation to the control, but in relation to the reference sample, only two samples. In relation to oxidative stress by hydrogen peroxide, 20 samples had statistical significance (p <0.05) in relation to the reference sample, 06 were more sensitive, and 14 were more resistant. At the zeta potential, only three samples presented significantly more electronegative values (p <0.05) than the reference sample. Finally, in the hemolysin production assay, no sample had hemolytic activity in the 06 blood types evaluated. The data of this study are relevant to public health, since they allow the knowledge of the molecular epidemiology of this species, as well as some virulence factors, which have been little described in Brazil, thus allowing to reinforce the monitoring and to implement control measures.