The organism described as the most common cause of aspergillosis is which?

• A. Aspergillus fumigatus
• B. Aspergillus niger
• C. Penicillium marneffei
• D. Candida albicans

Answer: (A)

Aspergillosis is most commonly caused by Aspergillus fumigatus. This environmental mold is widespread, and its tiny spores—about 2–3 micrometers—are easily inhaled and able to reach the deepest parts of the lung. In people with weakened immunity, these spores germinate and form invasive hyphae that invade tissue, driving the disease process. That combination of frequent exposure, small spore size, and tissue-invasive potential makes this species the leading cause. The other organisms listed are associated with different infections: Aspergillus niger can cause disease but less often; Penicillium marneffei (now Taloromyces marneffei) is a regional opportunistic pathogen; Candida albicans causes candidiasis rather than aspergillosis.