Antifungal and anti-biofilm activity of a new Spanish extract of propolis against Candida glabrata

Abstract

Background Resistance to traditional antifungal agents is a considerable health problem nowadays, aggravated by infectious processes related to biofilm formation, usually on implantable devices. Therefore, it is necessary to identify new antimicrobial molecules, such as natural products, to develop new therapeutic strategies to prevent and eradicate these infections. One promising product is propolis, a natural resin produced by honeybees with substances from various botanical sources, beeswax and salivary enzymes. The aim of this work was to study the effect of a new Spanish ethanolic extract of propolis (SEEP) on growth, cell surface hydrophobicity, adherence and biofilm formation of Candida glabrata, a yeast capable of achieving high levels of resistance to available anti-fungal agents. Methods The antifungal activity of SEEP was evaluated in the planktonic cells of 12 clinical isolates of C. glabrata. The minimum inhibitory concentration (MIC) of propolis was determined by quantifying visible growth inhibition by serial plate dilutions. The minimum fungicide concentration (MFC) was evaluated as the lowest concentration of propolis that produced a 95% decrease in cfu/mL, and is presented as MFC50 and MFC90, which corresponds to the minimum concentrations at which 50 and 90% of the C. glabrata isolates were inhibited, respectively. Influence on cell surface hydrophobicity (CSH) was determined by the method of microbial adhesion to hydrocarbons (MATH). The propolis effect on adhesion and biofilm formation was determined in microtiter plates by measurement of optical density (OD) and metabolic activity (XTT-assay) in the presence of sub-MIC concentrations of SEEP. Results SEEP had antifungal capacity against C. glabrata isolates, with a MIC50 of 0.2% (v/v) and an MFC50 of 0.4%, even in azole-resistant strains. SEEP did not have a clear effect on surface hydrophobicity and adhesion, but an inhibitory effect on biofilm formation was observed at subinhibitory concentrations (0.1 and 0.05%) with a significant decrease in biofilm metabolism. Conclusions The novel Spanish ethanolic extract of propolis shows antifungal activity against C. glabrata, and decreases biofilm formation. These results suggest its possible use in the control of fungal infections associated with biofilms.

Antibiofilm and Anti-Quorum Sensing Potential of Cycloartane-Type Triterpene Acids from Cameroonian Grassland Propolis: Phenolic Profile and Antioxidant Activity of Crude Extract

“…Propolis extract was previously shown to significantly reduce total biomass and the number of viable bacterial cells, and it was shown that the cells were damaged and disorganized both in the planktonic cells and sessile biofilm cells caused by treatment with propolis [ 43 ]. The good antimicrobial activity and moderate antibiofilm activity reported here is contrary to the good antibiofilm activity of propolis extracts reported against gram-positive and gram-negative bacteria, which effectively reduce or eliminate biofilms and planktonic cell growth [ 31 , 44 , 45 ]. However, moderate to low susceptibility of biofilms to propolis extracts were reported by other researchers [ 46 , 47 ] and hence are in conformity with our results.…”

Antifungal Properties of Chemically Defined Propolis from Various Geographical Regions

“…Antifungal activities of various extracts of propolis have been examined against several yeasts, such as Candida albicans, C. dubliniensis, C. glabrata, C. krusei, C. parapsisolis, C. tropicalis, Saccharomyces cerevisiae [13,[16][17][18]21,50,[54][55][56][57][60][61][62][63][64], as well as against molds, such as Alternaria solani, Alternaria alternata, Aspergillus niger, Aspergillus ochraceus, Botrytis cinerea, Cladosporium spp., Fusarium solani, Fusarium oxysporum, Mucor mucedo, Penicillium digitatum, Penicillium expansum, Penicillium chrysogenum, Rhizopus stolonifera, Rhodotorula mucilaginosa and Trichophyton spp. [9,19,43,64].…”

“…Oki ńczyc et al [50] showed that ethanolic extract of propolis inhibited filamentation of cells of C. albicans, germination of yeasts and increased production of the superoxide anion radical. A few studies showed that extracts of propolis are effective inhibitors of biofilm [16,53,54,57,[67][68][69]. Freires et al [54] observed that ethanolic extract of Brazilian propolis (types 3 and 13) can lead to disruption of the biofilm structures of Candida sp.…”

“…Moreover, Martorano-Fernandes et al [67] revealed that extract from Brazilian red propolis possessed inhibitory effects on the proliferation and diminished the metabolism of biofilms of C. albicans. Fernández-Calderón et al [16] showed that 70% ethanolic extract of Spanish propolis inhibited the fungal biofilm at sub-inhibitory concentrations of extract (0.1 and 0.05%). Gucwa et al [57] showed that values of minimum biofilm eradication concentration of Polish propolis extract were in the range of 0.04% to more than 1.25% (v/v) for C. glabrata, C. krusei, and C. albicans.…”

“…Propolis has shown mainly antifungal [8,9,[13][14][15][16][17][18][19][20][21][22], antibacterial [10,19,20,23,24], antiviral [20,[25][26][27][28][29], antiparasitic [5,20,30,31], anti-inflammatory [17,[32][33][34] and neuroprotective activity [35][36][37][38], and also anticancer properties [39][40][41][42].…”