What organism causes oral and vaginal candidiasis most commonly?

• A. Candida glabrata
• B. Cryptococcus neoformans
• C. Candida albicans
• D. Candida tropicalis

Answer: (C)

Oral and vaginal candidiasis are most commonly caused by Candida albicans because it is the species most frequently present as a harmless resident on mucosal surfaces and, under certain conditions, becomes pathogenic. C. albicans is well adapted to the oral and genital areas, able to switch from a yeast form to a filamentous hyphal form, which helps it adhere to and invade mucosal lining and form biofilms. This combination of being a common commensal and having virulence traits that promote overgrowth makes this species the leading cause of mucosal candidiasis, producing the classic oral thrush and vulvovaginal infection presentations.

Other Candida species can cause infections, but they are less commonly responsible for these mucosal conditions. Cryptococcus neoformans, for example, more often affects the lungs or central nervous system rather than the mucosal surfaces in healthy individuals.