Which of the following statements is true?

• A. Most pathogens colonize the surface of a person’s skin & cause disease without a portal of entry.
• B. Intestinal pathogens are usually inhaled via the nose.
• C. Pores in the skin are a common portal of entry for respiratory pathogens.
• D. If a pathogen is ingested but is unable to colonize within the host, it is unlikely to cause disease.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the concept of 'portal of entry' in microbiology, which refers to the site through which pathogens enter the host to initiate infection. Common portals include skin, respiratory tract, gastrointestinal tract, and mucous membranes.
2. Step 2: Analyze the first statement: 'Most pathogens colonize the surface of a person’s skin & cause disease without a portal of entry.' Recognize that the skin acts as a barrier, and pathogens usually require a breach or specific portal to cause disease, so this statement is generally false.
3. Step 3: Evaluate the second statement: 'Intestinal pathogens are usually inhaled via the nose.' Recall that intestinal pathogens typically enter through ingestion (oral route), not inhalation, making this statement incorrect.
4. Step 4: Consider the third statement: 'Pores in the skin are a common portal of entry for respiratory pathogens.' Understand that respiratory pathogens primarily enter through the respiratory tract (nose, mouth), not through skin pores, so this statement is false.
5. Step 5: Review the fourth statement: 'If a pathogen is ingested but is unable to colonize within the host, it is unlikely to cause disease.' Recognize that colonization is essential for many pathogens to establish infection; without colonization, disease is unlikely, making this statement true.