Of the following fungi, which is usually transmitted from person to person?
a. Blastomyces dermatitidis
b. Coccidioides immitis
c. Tricophyton rubrum
d. Aspergillus fumigatus

Verified step by step guidance

1. Step 1: Understand the nature of each fungus listed and their typical modes of transmission. This involves knowing whether they are primarily environmental fungi or those that infect humans and can be spread between people.
2. Step 2: Recognize that Blastomyces dermatitidis and Coccidioides immitis are dimorphic fungi typically acquired from environmental sources such as soil, and are not usually transmitted from person to person.
3. Step 3: Identify Aspergillus fumigatus as a common environmental mold that causes opportunistic infections, mainly through inhalation of spores from the environment, and is not transmitted between people.
4. Step 4: Note that Trichophyton rubrum is a dermatophyte fungus that infects keratinized tissues (skin, hair, nails) and is commonly transmitted from person to person through direct contact or contaminated surfaces.
5. Step 5: Conclude that among the options, the fungus usually transmitted from person to person is Trichophyton rubrum.

Key Concepts

Modes of Transmission in Fungi

Fungi can be transmitted through various routes including environmental exposure, inhalation of spores, or direct contact. Understanding the typical transmission mode helps identify which fungi spread from person to person versus those acquired from the environment.

Dermatophytes and Person-to-Person Transmission

Dermatophytes like Trichophyton rubrum infect keratinized tissues and are commonly spread via direct skin-to-skin contact or contaminated objects. This makes them the primary fungi transmitted between individuals.

Environmental Fungi and Opportunistic Infections

Fungi such as Blastomyces dermatitidis, Coccidioides immitis, and Aspergillus fumigatus are typically acquired from environmental sources like soil or decaying matter. They rarely transmit directly between people, often causing infections after inhalation of spores.