Final answer:
The yeast associated with causing vaginitis and otitis, and demonstrating elongated blastoconidia parallel to pseudohyphae on cornmeal Tween 80 agar, is Candida albicans. It is a common component of the human microbiota that can become pathogenic under certain conditions. C. albicans produces several virulence factors that assist in tissue invasion and contribute to its pathogenicity.
Step-by-step explanation:
The yeast in question that has been found in multiple human body sites and is mainly thought to cause vaginitis and otitis is Candida albicans. This yeast can cause various infections, including vaginal yeast infections, oral thrush, and cutaneous candidiasis. A defining characteristic of C. albicans is its ability to grow on cornmeal Tween 80 agar, where its elongated blastoconidia lie parallel to pseudohyphae, creating a pattern that is reminiscent of logs lying on a stream. The distinctive formation of pseudohyphae alongside the blastoconidia and the yeast's dimorphic nature are definitive diagnostic indicators.
Furthermore, Candida albicans contributes to the normal microbiota of the human body in locations such as the skin, mouth, intestine, and vagina. It becomes pathogenic under certain conditions, such as an immuno-compromised state or after a disturbance in the normal flora, often due to antibiotic therapy. C. albicans produces virulence factors, including adhesins and exoenzymes such as proteases and phospholipases, which facilitate tissue invasion and overgrowth. Its capacity to change phenotypes helps it protect itself from the immune system, potentially leading to disease.