The Effect of Nutritive and Non-Nutritive Sweeteners on the Growth, Adhesion, and Biofilm Formation of Candida albicans and Candida tropicalis

Abstract

Objective: To determine the effect of glucose, sucrose, and saccharin on growth, adhesion, and biofilm formation of Candida albicans and Candida tropicalis.

Materials and methods: The growth rates of mono-cultures of planktonic C. albicans and C. tropicalis and 1:1 mixed co-cultures were determined in yeast nitrogen broth supplemented with 5% (30 mM) and 10% (60 mM) glucose, sucrose, and saccharin, using optical density measurements at 2-h intervals over a 14-h period. Adhesion and biofilm growth were performed and the growth quantified using a standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The biofilm architecture was visualized using scanning electron microscopy. One- and two-way analysis of variance (ANOVA) was performed to analyse the differences among multiple means.

Results: The highest planktonic growth was noted in 5% glucose after 14 h (p < 0.05). No significant planktonic growth was observed in either concentration of saccharin. Both the concentrations of glucose and sucrose elicited significantly increased adhesion from MTT activity of 0.017 to >0.019 in mono- as well as co-cultures (p < 0.05), whilst the lower concentration of saccharin significantly dampened the adhesion. Maximal biofilm growth was observed in both species with the lower concentration of sucrose (5%), although a similar concentration of saccharin abrogated biofilm development: the highest MTT value (>0.35) was obtained for glucose and the lowest (>0.15) for saccharin.

Conclusion: In this study, glucose and sucrose accelerated the growth, adhesion, and biofilm formation of Candida species. However, the non-nutritive sweetener saccharin appeared to dampen, and in some instances suppress, these virulent attributes of Candida.

Keywords: Adhesion; Biofilms; Candida species; Glucose; Growth sucrose; Saccharin.

Fig. 1

a Growth curves of planktonic Candida albicans and Candida tropicalis and 1:1 mixed co-culture grown in glucose, sucrose, and saccharin 5$ (mean ± 2 SD of 3 independent experiments performed in triplicate). b Growth curves of planktonic C. albicans and C. tropicalis and 1:1 mixed co-culture grown in glucose, sucrose, and saccharin 10$ (mean ± 2 SD of 3 independent experiments performed in triplicate).

Fig. 2

Results of the MTT assay. Adhesion of C. albicans, C. tropicalis, and mixed species in yeast nitrogen broth (YNB) supplemented with 5 and 10$ glucose, sucrose, and saccharin. In this experiment YNB without sugar was used as negative control. All error bars represent the mean ± 2 SD.

Fig. 3

a Biofilm development of C. albicans, C. tropicalis, and mixed species in yeast nitrogen broth (YNB) supplemented with 5$ glucose, sucrose, and saccharin as determined by MTT assay (mean ± 2 SD of 3 independent experiments performed in triplicate). b Biofilm development of C. albicans, C. tropicalis, and mixed species in YNB supplemented with 10$ glucose, sucrose, and saccharin as determined by MTT assay (mean ± 2 SD of 3 independent experiments performed in triplicate).

Fig. 4

a Electron microscopic appearance of 72-h mature biofilms of C. albicans with 5$ sucrose. Scale, 20 µm. b Electron microscopic appearance of 72-h mature biofilms of C. albicans and C. tropicalis mixed species co-culture with 5$ sucrose. Scale, 20 µm. c Electron microscopic appearance of 72-h mature biofilms of C. albicans with 5$ saccharin. Scale, 20 µm.