Activity of the Ethanolic Extract of Propolis (EEP) as a Potential Inhibitor of Quorum Sensing-Mediated Pigment Production in Chromobacterium violaceum and Virulence Factor Production in Pseudomonas aeruginosa

Bacteria are capable of the organized expression of specific sets of genes through a recently discovered phenomenon termed quorum sensing (QS). Researchers are beginning to focus their efforts into the discovery of potential QS inhibitors for the development of novel antipathogenic drugs. This study investigated the QS inhibitory potential of the ethanolic extract of propolis (EEP) in the test organism Chromobacterium violaceum ATCC 12472 and the opportunistic organism Pseudomonas aeruginosa PAO1. Results of this study showed EEP as a potential inhibitor of QS-mediated violacein production in C. violaceum. EEP was thereby subjected to further testing on its ability to interfere with virulence factor production and biofilm formation in P. aeruginosa. It was found that EEP was able to significantly affect the LasA and LasB protease activities. In addition, changes in the protease activity were observed with no significant effects on the growth of the organism. This implies that changes in the enzyme activities are unrelated to bactericidal consequences. However, it was also found that EEP inhibited the biofilm formation of P. aeruginosa PAO1 at lower concentrations but not at higher concentrations. This suggests the need for further investigations to be made on the effect of EEP on the maturation and differentiation of biofilms.