A 38-year-old woman with poorly controlled type 2 diabetes mellitus presents with vulvovaginal itching and thick white vaginal discharge for 2 weeks. On examination, vulvar erythema and edema are noted. Wet mount microscopy shows budding yeast cells and pseudohyphae. Culture on Sabouraud dextrose agar at 37°C grows white, creamy colonies that produce germ tubes in human serum. Which of the following is the most likely organism and the most appropriate first-line treatment?

Explanation

## Organism Identification **Key Point:** Candida albicans is the most common cause of vulvovaginal candidiasis (VVC), accounting for ~90% of cases. The clinical presentation—thick white discharge, vulvar erythema, and pruritus in a hyperglycemic patient—is classic. **High-Yield:** The germ tube test is the gold standard rapid identification method for C. albicans. Incubation of the isolate in human serum at 37°C for 2–3 hours produces characteristic germ tubes (tube-like hyphal projections) that are pathognomonic. ## Pathogenesis in Diabetes Hyperglycemia impairs neutrophil function and cell-mediated immunity, predisposing to candidal overgrowth in the vaginal mucosa. C. albicans is a dimorphic fungus; the yeast form colonizes the vaginal epithelium, while pseudohyphae and hyphae promote tissue invasion and inflammation. ## Treatment | Agent | Dose | Indication | Notes | |-------|------|-----------|-------| | Fluconazole | 150 mg single dose | Uncomplicated VVC (first-line) | Oral, well-absorbed, excellent vaginal penetration | | Miconazole/Clotrimazole | Topical (3–7 days) | Uncomplicated VVC (alternative) | Azole creams; slower onset | | Amphotericin B | Reserved for severe/invasive | Immunocompromised or non-albicans | Nephrotoxic; not for uncomplicated VVC | **Clinical Pearl:** A single 150 mg dose of fluconazole achieves cure rates >90% in uncomplicated VVC. Recurrent VVC (≥4 episodes/year) may require prophylactic fluconazole 150 mg weekly for 6 months. ## Why Germ Tube Test Identifies C. albicans 1. C. albicans produces true hyphae and germ tubes (hyphal outgrowths without a septum at the point of origin). 2. Pseudohyphae (budding cells arranged in chains) are also visible but are not specific to C. albicans. 3. The germ tube test is rapid (2–3 hours), inexpensive, and has >95% sensitivity and specificity for C. albicans among Candida spp. **Mnemonic:** **GERM** = **G**erm tube, **E**arly identification, **R**apid test, **M**ost common Candida.