Aplicação do inibidor de Quorum sensing curcumina como modulador de biofilmes bacterianos

Abstract

Biofilm is the main form of bacterial organization in nature. It is a complex microbial community that has an intercellular signaling system called quorum sensing, mediated by molecules called auto-inducers. Several chronic and hospital infections can be associated with the formation of biofilms and, because of the greater resistance that biofilms present to antimicrobials, the treatment of such infections is difficult, and it is necessary to search for therapeutic alternatives, such as the quorum sensing inhibitor curcumin. The objective of this work was to evaluate the in vitro action of the quorum sensing inhibitor curcumin against bacterial biofilms in formation and mature. The study was carried out with 24 strains of Gram positive and Gram negative bacteria. The minimum inhibitory concentration (MIC) test was done by microdilution on U-bottom plates, as recommended by the Clinical Laboratory Standards Institute. The modulating effect of curcumin on growing biofilms and mature biofilms was evaluated on flat bottom plates using the concentrations of 513, 51 and 25 μM curcumin. The metabolic activity of the biofilm was evaluated with resazurin, while the biomass was quantified by the crystal violet technique. Curcumin showed inhibition of planktonic bacteria, with a MIC of 513 μM. Curcumin did not show activity against biofilms in the formation of Gram positive bacteria. However, Gram negative growth was detected in the highest concentration tested (513 μM). In mature biofilms, the curcumin induced their growth in the highest concentration used, both in Gram positive cocci and Gram negative bacilli. Thus, greater activity of curcumin was observed in the induction of biofilm growth by Gram negative bacilli. These results possibly show another type of action of this compound, suggesting that it interfere in quorum sensing modulation during the biofilm dispersion phase. However, additional experiments are needed to define its action spectrum.