An in vitro study on the antifungal and antibiofilm activities of probiotic bacteria against Candida species isolated from orthodontic appliances and dental caries

Abstract

Candida species are opportunistic pathogens that may cause infections in predisposed persons. This work aimed to detect the antifungal and antibiofilm potentials of Lactobacillus acidophilus and Lactobacillus plantarum supernatants on Candida spp. About 60 % and 80 % of Candida isolates were recovered from saliva samples of 20 patients with fixed orthodontic appliances, and 20 children having dental caries, respectively. The antifungal susceptibility of Candida spp. was investigated using disk diffusion assay. C. albicans strains showed low resistance to fluconazole (15 %) and amphotericin B (10 %). Using the agar well diffusion assay, both L. acidophilus and L. plantarum supernatants inhibited the in vitro growth of all tested Candida spp. with inhibition zone diameters of (11-19 mm) and (7-16 mm), respectively. On observing the effects of L. plantarum and L. acidophilus supernatants on Candida cells’ morphology; the light microscopic examination demonstrated the inhibition in germ tube formation of all tested C. albicans with percentages of 68 % and 53 %, and for C. krusei with inhibition percentages of 69 % and 59 %, respectively. L. acidophilus and L. plantarum strains showed high co-aggregation ability with C. albicans strains with ranges of 42-49 % and 30-35 %, respectively. The antibiofilm activities of the two Lactobacillus supernatants were determined using the tissue culture plate assays. Significant inhibition of biofilms formation by Candida spp. was recorded on treatment with L. plantarum and L. acidophilus supernatants, with reduction percentages of 50-72 % and 74-85 %, respectively.