**Core Concept**
Candidiasis is a type of fungal infection caused by Candida species, particularly Candida albicans. It can manifest as mucocutaneous or systemic infections, depending on the site and severity of the disease. The pathogenesis of candidiasis involves the adhesion of Candida to the host cells, followed by invasion and colonization.

**Why the Correct Answer is Right**
Candidiasis is characterized by the formation of biofilms, which are complex communities of microorganisms that adhere to host tissues and are resistant to antifungal agents. The adhesion of Candida to host cells is facilitated by the expression of adhesins, such as Als3p, which interact with host receptors like integrins. Once Candida has colonized the host, it can invade and cause tissue damage, leading to the symptoms of candidiasis.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while Candida can cause opportunistic infections in immunocompromised patients, it is not the primary cause of candidiasis in healthy individuals.
**Option B:** Incorrect because while antifungal agents like fluconazole can be used to treat candidiasis, they are not the primary mechanism of defense against Candida infections.
**Option C:** Incorrect because while Candida can cause systemic infections in severely immunocompromised patients, it is not a characteristic of all candidiasis cases.

**Clinical Pearl / High-Yield Fact**
Candidiasis is a common opportunistic infection in patients with HIV/AIDS, and its diagnosis requires a combination of clinical suspicion, laboratory tests, and imaging studies. It is essential to consider candidiasis in the differential diagnosis of patients with unexplained fever, rash, or mucocutaneous lesions.

**Correct Answer:** C.