Which statement is NOT true about the resident microbiota of the respiratory tract?

• A. Resident microbiota in the upper respiratory tract can help prevent colonization by pathogens.
• B. The composition of respiratory tract microbiota can be influenced by environmental factors.
• C. All bacteria found in the respiratory tract are pathogenic.
• D. The lower respiratory tract is typically sterile in healthy individuals.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of resident microbiota, which refers to the microorganisms that normally live in a specific area of the body without causing disease. In the respiratory tract, these microbes play important roles in health.
2. Step 2: Review the statements given about the respiratory tract microbiota. Identify which statements are true based on microbiological principles: for example, resident microbiota in the upper respiratory tract often prevent pathogen colonization, and environmental factors can influence microbiota composition.
3. Step 3: Recall that the lower respiratory tract is generally sterile in healthy individuals, meaning it does not normally harbor resident microbiota, which supports one of the statements as true.
4. Step 4: Analyze the statement 'All bacteria found in the respiratory tract are pathogenic.' Since resident microbiota are typically non-pathogenic and can be beneficial, this statement contradicts the concept of resident microbiota and is therefore false.
5. Step 5: Conclude that the statement which is NOT true about the resident microbiota of the respiratory tract is the one claiming all bacteria found there are pathogenic.