The yeast Candida albicans does not normally cause disease because of which of the following?

• A. its inability to survive at human body temperature
• B. its lack of metabolic activity in the presence of oxygen
• C. its exclusive presence in sterile body sites
• D. the protective effects of the host's normal microbiota and immune system

Answer: (D)

Verified step by step guidance

1. Understand that Candida albicans is a yeast commonly found as part of the normal human microbiota, especially on mucosal surfaces such as the mouth, gut, and vagina.
2. Recognize that it does not normally cause disease because the host's immune system and the protective effects of the normal microbiota keep its growth and pathogenic potential in check.
3. Evaluate the incorrect options: it can survive at human body temperature, it is metabolically active in the presence of oxygen, and it is not exclusively present in sterile body sites (it is often found in non-sterile sites).
4. Focus on the concept of microbial antagonism, where the normal microbiota competes with potential pathogens like Candida albicans, preventing their overgrowth.
5. Conclude that the balance maintained by the host's immune defenses and the normal microbiota is the key reason Candida albicans does not normally cause disease.