Microbiology MCAT Practice Question
A 32-year-old man with HIV/AIDS (CD4+ count 45 cells/μL) presents with persistent oral candidiasis despite fluconazole prophylaxis. Oral swabs are cultured and Candida albicans is isolated. Microscopic examination reveals both yeast and filamentous hyphal forms in the same culture specimen. The clinician notes that this organism's ability to switch between morphologies is regulated by environmental factors including temperature, pH, and presence of serum. Which of the following best explains the evolutionary advantage of morphological dimorphism in C. albicans?
Answer choices
- AThe hyphal form has a larger surface area for nutrient absorption, while the yeast form facilitates dissemination through the bloodstream and colonization of multiple tissue sites
- BThe yeast form is more susceptible to antifungal agents, allowing the organism to purge deleterious mutations and maintain genetic fitness
- CThe hyphal form breaches epithelial barriers and invades tissue, while the yeast form evades neutrophil-mediated killing and can be phagocytosed without triggering inflammatory responsesCorrect answer
- DThe yeast form enables sexual reproduction and genetic recombination, while the hyphal form is metabolically dormant and resistant to starvation
- EMorphological switching increases expression of virulence factors such as secreted aspartyl proteases and phospholipases regardless of fungal form
- FThe hyphal form preferentially colonizes the oral cavity while the yeast form is restricted to the gastrointestinal tract
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