Which of the following bacterial genera is composed of fibers known to cause lung disease?

• A. Actinomyces
• B. Mycobacterium
• C. Nocardia
• D. Streptomyces

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the question is asking about bacterial genera composed of fibers that are known to cause lung disease. This implies the bacteria have filamentous or fibrous structures and are associated with respiratory infections.
2. Step 2: Review the characteristics of each genus: Actinomyces, Mycobacterium, Nocardia, and Streptomyces. Focus on their morphology (fiber-like structures) and their clinical relevance to lung disease.
3. Step 3: Recognize that Actinomyces and Streptomyces are filamentous bacteria but are primarily associated with different types of infections (Actinomyces with oral/facial infections, Streptomyces mostly environmental and antibiotic producers).
4. Step 4: Note that Mycobacterium includes species like Mycobacterium tuberculosis, which causes lung disease but is not composed of fibers; it is an acid-fast bacillus.
5. Step 5: Identify Nocardia as a genus of filamentous, partially acid-fast bacteria known to cause pulmonary infections resembling tuberculosis, making it the genus composed of fibers linked to lung disease.