A 32-year-old woman with poorly controlled type 2 diabetes mellitus (HbA1c 10.2%) presents with vulvovaginal itching, burning, and thick white vaginal discharge for 2 weeks. On speculum examination, white plaques are visible on the vaginal wall and cervix. Gram stain of vaginal discharge shows budding yeast cells and pseudohyphae. Culture on Sabouraud dextrose agar at 37°C grows cream-coloured, smooth colonies. The organism produces germ tubes in human serum at 37°C within 2–3 hours. Which Candida species is most likely responsible for this infection?

Explanation

## Diagnosis: Candida albicans Vulvovaginitis ### Clinical Presentation The patient presents with classic vulvovaginal candidiasis (VVC) in the setting of hyperglycaemia, a well-known risk factor. The thick white discharge, visible plaques, and burning sensation are hallmark features of *Candida albicans* infection. ### Microbiological Identification **Key Point:** *Candida albicans* is the most common cause of vulvovaginal candidiasis, accounting for 80–90% of cases. **High-Yield:** The germ tube test is the gold standard rapid identification method for *C. albicans*. A positive germ tube test (formation of true hyphae in human serum at 37°C within 2–3 hours) is pathognomonic for *C. albicans*. | Feature | C. albicans | C. glabrata | C. auris | C. tropicalis | |---------|-------------|-------------|---------|---------------| | **Germ tube test** | Positive | Negative | Negative | Negative | | **Pseudohyphae** | Yes | No | No | Yes | | **Colony morphology** | Cream, smooth | Small, flat | Pink/purple | Cream, smooth | | **Common site** | Vagina, oral | Vagina (resistant) | Nosocomial | Vagina | | **Chlamydospore formation** | Yes | No | No | Yes | ### Pathophysiology Hyperglycaemia increases vaginal glucose concentration, promoting yeast proliferation. *C. albicans* is dimorphic, existing as both yeast and filamentous forms, which enhances tissue invasion and virulence. **Clinical Pearl:** Recurrent vulvovaginal candidiasis (≥4 episodes/year) warrants screening for diabetes mellitus and HIV infection. ### Management - Topical azoles (clotrimazole, miconazole) for uncomplicated VVC - Oral fluconazole (150 mg single dose) for moderate-to-severe disease - Glycaemic control is essential to prevent recurrence [cite:Textbook of Microbiology Baveja 5e Ch 24]