Which organism is most commonly associated with fungal overgrowth such as thrush in immunocompromised patients?

• A. Bacterial pneumonia
• B. Parasitic infection
• C. Herpes simplex
• D. Candida albicans

Answer: (D)

Oral thrush is an opportunistic fungal overgrowth caused most often by Candida albicans. This organism normally resides on mucosal surfaces, but when the immune system is compromised (or when the normal flora is disrupted by factors like antibiotics), it can proliferate and form the white, curd-like plaques seen in thrush. In immunocompromised patients, Candida albicans is the usual culprit and can even spread beyond the mouth in severe cases. The other options describe bacteria, a parasite, or a virus, which do not cause this characteristic fungal overgrowth. So the best answer is Candida albicans.