Atividade antimicrobiana e antibiofilme do sobrenadante de cepas de lactobacillus cell-free sobre isolados de escherichia coli farmacoresistentes

Abstract

The term biofilm describes the life form characterized by the microbial adhesion to a surface with the production of extracellular polymeric substances, constituting a gelatinous network that protects the cells. Biofilms formation is involved in the increasing incidence of important multidrug resistant bacterial pathogens to conventional antimicrobial therapies, being verified the presence of enterobacteria isolated from fresh foods resistant to multiple antibiotics. Given this context, it is necessary to search for new forms of microbial control. Lactic acid bacteria, including Lactobacillus species, have been associated with the prevention or dispersion of biofilms formed by pathogenic microorganisms. Therefore, the aim of this work was to evaluate the antimicrobial and antibiofilm activity of the cell-free supernatants produced by Lactobacillus strains on multi-drug resistant E. coli isolates. For this, the profile of antimicrobial susceptibility of E. coli strains was identified by the VITEK®2 automated system. For the evaluation of the antagonistic activity of probiotics, the Spot Overlay technique was used, with measurement of the inhibition halos. The cell-free supernatant produced by Lactobacillus was tested for its antimicrobial effect by plaque microdilution of the supernatant with the concentrations ranging 6,25 a 50%. The antibiofilm action was evaluated after treatment of preformed biofilm for 12 h, using a Crystal Violet staining technique to verify changes in biofilm biomass. As a result, the samples were found to be resistant to ampicillins, cephalothin and quinolones. As for the antagonism test, all probiotic strains demonstrated high inhibitory capacity (inhibition scores > 6 mm) against multiresistant E. coli isolates. The isolates were susceptible to antimicrobial activity of the supernatants produced, with Minimal Inhibitory and Bactericidal Concentrations ranging from 12.5 to 50%. However, no effect was observed after neutralization, which indicate that the inhibitory action may be related to the production of organic acids. Regarding the antibiofilm effect, all the analyzed probiotics were capable to reduce the preformed biofilm, standing out the commercial strain, that was capable to inhibit around 50% of the biomass. Therefore, the cellfree preparations produced by Lactobacillus from the present study may represent tools for a possible overcome of resistance mechanisms presented by E. coli isolates.