Nanopartículas de prata biogênicas e de extratos de própolis em biofilmes de Corynebacterium pseudotuberculosis

Abstract

Corynebacterium pseudotuberculosis is a Gram-positive and intracellular bacterium that causes caseous lymphadenitis (CL) in small ruminants, a chronic disease characterized by the development of encapsulated granulomas in superficial and visceral lymph nodes, as well as in various organs. An important feature of chronic bacterial infections is the development of biofilm. Considering this scenario, the aim of this study was to evaluate the biofilm formation capacity of C. pseudotuberculosis and to determine the susceptibility of biofilm-forming bacterial isolates to ethanolic and supercritical extracts of propolis, and to silver nanoparticles (AgNP). The broth microdilution methodology, the analysis of the disruption of the consolidated biofilm and the interference in the formation of biofilm assays were used to determine the sensitivity of the isolates to antimicrobials. Mature biofilms were visualized by Scanning Electron Microscopy. The ethanolic extracts of green propolis and supercritical red propolis were not effective in inhibiting the C. pseudotuberculosis consolidated biofilm but were able to interfere in the formation of bacterial biofilm. The AgNPs acted for 48 hours in C. pseudotuberculosis controlling the change between planktonic and sessile forms, decreasing the fixation and colonization in a microplate. The colloidal AgNP solution significantly reduced the consolidated biofilms of C. pseudotuberculosis. The SEM images showed that the AgNP were able to disrupt the bacterial biofilm, and that there were morphological changes in the bacteria present in the treated biofilms. It can be concluced that AgNPs con be considered a promising therapeutical agent in the treatment of the caseous lymphadenitis in small ruminants.