Inhalation of fungal spores can cause primary lung infections. Of the following organisms, which one is most likely to be associated with this mode of transmission?
**Core Concept**
Primary pulmonary fungal infections are caused by organisms that are inhaled as airborne spores and establish infection directly in the lungs. Among fungi, *Coccidioides immitis* is a thermally dimorphic fungus that produces spores in the environment, which are inhaled and germinate in the lungs, leading to coccidioidomycosis.
**Why the Correct Answer is Right**
*C. immitis* is a thermally dimorphic fungus that grows as a mold in the environment and produces airborne spores. When inhaled, these spores germinate in the lungs and cause primary pulmonary infection, leading to coccidioidomycosis, a classic example of inhalational fungal disease. The spores are highly resistant and commonly found in soil, especially in arid regions like the southwestern U.S. This organism is specifically known for causing primary pulmonary infection via inhalation.
**Why Each Wrong Option is Incorrect**
Option B: *S. schenckii* causes sporotrichosis, which is a subcutaneous infection from skin exposure, not inhalation.
Option C: *C. albicans* is a commensal yeast that causes opportunistic infections, typically in immunocompromised hosts, not primary pulmonary disease via spore inhalation.
Option D: *T. tonsurans* is a dermatophyte that causes scalp and skin infections, transmitted through direct contact, not inhalation.
**Clinical Pearl / High-Yield Fact**
Coccidioides immitis is the only fungal species among these options that causes a primary pulmonary infection via inhalation of spores. Remember: "Inhalation = C. immitis; skin contact = S. schenckii or T. tonsurans."
✓ Correct Answer: A. C. immitis