Antifungal Activity of Mexican Propolis on Clinical Isolates of Candida Species

Abstract

Infections caused by micro-organisms of the genus Candida are becoming a growing health problem worldwide. These fungi are opportunistic commensals that can produce infections-clinically known as candidiasis-in immunocompromised individuals. The indiscriminate use of different anti-fungal treatments has triggered the resistance of Candida species to currently used therapies. In this sense, propolis has been shown to have potent antimicrobial properties and thus can be used as an approach for the inhibition of Candida species. Therefore, this work aims to evaluate the anti-Candida effects of a propolis extract obtained from the north of Mexico on clinical isolates of Candida species. Candida species were specifically identified from oral lesions, and both the qualitative and quantitative anti-Candida effects of the Mexican propolis were evaluated, as well as its inhibitory effect on C. albicans isolate's germ tube growth and chemical composition. Three Candida species were identified, and our results indicated that the inhibition halos of the propolis ranged from 7.6 to 21.43 mm, while that of the MFC and FC₅₀ ranged from 0.312 to 1.25 and 0.014 to 0.244 mg/mL, respectively. Moreover, the propolis was found to inhibit germ tube formation (IC₅₀ ranging from 0.030 to 1.291 mg/mL). Chemical composition analysis indicated the presence of flavonoids, including pinocembrin, baicalein, pinobanksin chalcone, rhamnetin, and biochanin A, in the Mexican propolis extract. In summary, our work shows that Mexican propolis presents significant anti-Candida effects related to its chemical composition, and also inhibits germ tube growth. Other Candida species virulence factors should be investigated in future research in order to determine the mechanisms associated with antifungal effects against them.

Keywords: Mexican propolis; anti-Candida activity; bioactive compounds; chemical composition; germ tube.

Figure 1

Representative photographs of the identification of the different species of Candida: (A) Upper half of Petri dish is CC4 (C. albicans), lower half of Petri dish is CC5 (C. krusei); (B) Upper and lower halves of Petri dish are CC10 (C. albicans); (C) Upper half is CC6 (C. glabrata), lower half is CC8 (C. albicans).

Figure 2

(A–E) Representative photographs of the inhibition halos of the antifungal activity of Mexican propolis against different species of Candida. (F) Representative photograph of the inhibition halos of Nystatin against CC1 (C. krusei).

Figure 3

Representative microphotographs (40×) of the inhibitory effect of propolis on the germ tube growth of C. albicans. Black arrows point to the germ tubes of C. albicans. Red arrows point to C. albicans without germ tube growth. (A,D) are the germ tube growth of C. albicans from CC2 and CC7, respectively, after four hours of culture. (B) Complete inhibition of the germ tube in CC2 with a concentration of 1250 µg/mL of Mexican propolis. (C) Germ tube growth inhibition of 51.54% in CC2 at 118 µg/mL of propolis. (E) Complete inhibition of the germ tube at 2500 µg/mL in CC7. (F) Germ tube growth inhibition of 60.08% in CC7 at 28 µg/mL of propolis.

Figure 4

Structural formulas of flavonoids present in Mexican propolis.