Estudo da hipermutabilidade em espécies do complexo Burkholderia cepacia isoladas de pacientes com fibrose cística

Abstract

The Burkholderia cepacia complex (BcC) consist of 24 species, most of all are associated with chronic pulmonary infection in patients with cystic fibrosis (CF) and are related to decline of pulmonary function. The lung environment of CF patients exerts selective pressure on pathogens, leading to the emergence of adaptive characteristics for their persistence. Among them, hypermutability (HPM), which is characterized by an increase rate of spontaneous mutation, and is observed mainly in chronic infections. The relationship between the HPM and antibiotic resistance have been described. This study aimed to investigate the occurrence of HPM in BcC species isolated from CF patients with chronic lung infection. Weanalysed 147 CBc isolates from January 2010 to July 2018 obtained from 30 CF patients assisted in two reference centers in Rio de Janeiro. The HPM characterization was performed using the determination of the mutation frequency by growth in media without (wild population) and containing rifampicin (subpopulations). The isolates were submitted to disk-diffusion test. Twenty-six isolates (17.7%) were classified as HPM, and they were observed in 12 (40%) patients colonized by BcC. The HPM characterization among the BcC species showed this phenotype was detected in three of the seven species identified: B. multivorans was the species with the highest percentage (n = 6/18; 33; 3%), followed by B. cenocepacia (n=17/57; 29.8%), regardless of genomovar, and B. vietnamiensis (3/65; 4.61%). Among B. cenocepacia (n = 57), the genomonar IIIA showed the highest HPM rates (12/26; 46.15%), probably it represents the most virulent strain of the species, with the greatest potential for adaptation to stressful environments, such as the lung of CF patients. The temporal analysis of HPM distribution per patient, showed several scenarios.The majority of patients showed only one HPM isolate during the follow-up, and only two patients showing all (P2) or most of all (P26) isolates classified as HPM. The presence of HPM and non-HPM strains of the same species (B. cenocepacia IIIA) with long intervals of time, was observed (P6), indicating a probable re-infection by the same species. The detection of the same species (B. cenocepacia IIIA) HPM and non-HPM phenotype in the same clinical specimen (P13), suggests the possibility of coexistence between the wild strain and the subpopulation. None difference was observed in the antibiotic resistance profile between wild isolates and rifampin-resistant subpopulations. Although, here, this relation could not be established, , it is important highlighting that mutations may play an important role in the selection of genes that can work as an advantage metabolic adaptations, quorum-sensing, adherence to the surface of the respiratory epithelium and the survival of subpopulations in environments with low oxygen levels.