PP13- Effectiveness of Sri Lankan sweet potato varieties (reddish and whitish) as an alternative media for potato dextrose agar to isolate Candida albicans.

Abstract

Introduction

Candida albicans are commonly isolated using Sabouraud Dextrose Agar (SDA), Potato Dextrose Agar (PDA), and Potato Dextrose Broth (PDB), which remain expensive. Exploring alternative, cost-effective media is crucial in Sri Lanka.

Objectives

The objective was to determine the minimum effective concentration (MEC) of sweet potato infusions (SPI) required to prepare sweet potato agar (SPA) and sweet potato broths (SPB) with and without the addition of dextrose, compared to PDA and PDB.

Design, setting, and methods

Six SPI concentrations (10, 50, 100, 200, 300, and 400 g/L) were prepared from both reddish and whitish sweet potatoes, with and without dextrose, and used to formulate SPA and SPB following the PDA preparation method. Candida albicans (ATCC 10231) was inoculated at McFarland 0.5. All media were incubated at 25°C for 48 hours.

Colony count, macroscopic and microscopic appearance, and germ tube formation were assessed and compared with PDA and PDB. Each concentration was tested in triplicate and repeated. Data were analyzed using an ANOVA test.

 Results

The mean colony count for PDA was 550 mL⁻¹. For SPA, the MECs were 200 g/L (whitish, without dextrose), 100 g/L (whitish, with dextrose), 300 g/L (reddish, without dextrose), and 200 g/L (reddish, with dextrose), with colony counts of 548, 542, 532, and 528 mL⁻¹, and corresponding p-values of 0.99, 0.85, 0.63, and 0.11, indicating no significant difference from PDA. The mean direct germ tube count for PDB was 3.92 x 10⁴ mL⁻¹. Similar MECs to those observed in SPA were found in SPB, compared to PDB. For these MECs, corresponding direct germ tube counts were 4.0 x 10⁴ mL⁻¹, 3.83 x 10⁴ mL⁻¹, 4.0 x 10⁴ mL⁻¹, and 3.96 x 10⁴ mL⁻¹, with p-values of 0.782, 0.851, 0.428, and 1.00, respectively. Colonies on all media were round, creamy-white, smooth, and 1–3 mm in diameter. Microscopically, cells showed true hyphae, pseudohyphae, and clustered blastospores. Germ tube tests confirmed C. albicans.

Conclusion

Both reddish and whitish sweet potato varieties can serve as alternatives to potato and dextrose in the preparation of PDA and PDB for culturing Candida albicans. However, the whitish variety shows effectiveness at lower concentrations compared to the reddish variety.