REVIEW OF MEDICAL MICROBIOLOGY

MEDICAL MYCOLOGY

14. A leukemic patient complains of respiratory symptoms including frequent coughs. X-ray examination of the left lung reveals the presence of a coin-sized lesion characterized by the presence of an air space surrounding the cavity. Sputa of the patient show the presence of thick and uniformly septate hyphae. The culture of sputa yields hairy colonies firmly adhering to the agar surface. The patient _Fs tuberculin test is negative. The most likely cause of the respiratory problem of this patient is:

1. tuberculosis
2. mucormycosis
3. aspergillosis
4. histoplasmosis
5. candidiasis

(C) Both clinical symptoms and cultural characteristics of the causative agent suggest that the diagnosis of this patient is aspergillosis, a common opportunistic infection seen in compromised hosts. Tuberculosis is unlikely because the patient s tuberculin skin test is negative. The causative fungus for mucormycosis (phycomycosis) produces characteristic nonseptate hyphae in vivo. Histoplasma capsulatum, which causes histoplasmosis in humans, grows in yeast form in the infected person. Candida, causative agent for candidiasis, does not produce hairy colonies on the agar surface. (Joklik et al, pp. 1135-1152; Ryan et al, pp. 697-599)

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