Which type of specimen is typically collected to diagnose respiratory infections such as whooping cough (pertussis) and croup?

• A. Stool sample
• B. Urine sample
• C. Blood culture
• D. Nasopharyngeal swab

Answer: (D)

Verified step by step guidance

1. Understand the nature of the infection: Respiratory infections like whooping cough (pertussis) and croup primarily affect the upper respiratory tract, including the nose and throat.
2. Identify the site where the causative bacteria or viruses are most likely to be present in high numbers during infection, which is typically the nasopharynx (the upper part of the throat behind the nose).
3. Recognize that to diagnose these infections accurately, a specimen must be collected from the site where the pathogen resides, ensuring the highest chance of detecting the infectious agent.
4. Evaluate the options given: stool samples and urine samples are generally used for gastrointestinal or urinary infections, while blood cultures are used for systemic infections; none of these are ideal for respiratory pathogens localized in the nasopharynx.
5. Conclude that the nasopharyngeal swab is the appropriate specimen type because it collects cells and secretions from the nasopharynx, where Bordetella pertussis (the bacterium causing whooping cough) and viruses causing croup are most likely to be found.