Oral candidiasis is a Candida yeast infection of the oral mucosa. Which organism is responsible?

• A. Candida
• B. Streptococcus
• C. Escherichia coli
• D. Aspergillus

Answer: (A)

Oral candidiasis is caused by a yeast, specifically Candida species, most commonly Candida albicans. Candida is normally present in the mouth, but overgrowth can occur when the balance of microbes is disrupted—for example after antibiotic use, with immune compromise, wearing dentures, or diabetes. In the mouth, Candida appears as budding yeast cells and can form pseudohyphae, which helps it adhere to and invade mucosal surfaces, leading to the characteristic white patches and soreness. The other organisms listed are a bacterium (Streptococcus), another bacterium (Escherichia coli), and a mold (Aspergillus), none of which cause this yeast infection of the oral mucosa.