Question

A 7-month-old child presents with a history of bouts of cough ending with a whoop. The immunization history is not available. What is the best way to confirm the diagnosis?

• A. Nasopharyngeal swab
• B. Cough plate culture
• C. Tracheal aspirate
• D. Oral swab

Hint:

Sample the site where Bordetella pertussis actually colonizes.

Answer 1

The Correct Option is A

Step 1: Paroxysmal cough ending in an inspiratory whoop in an under-immunized infant is the classic picture of whooping cough caused by Bordetella pertussis.
Step 2: B. pertussis selectively colonizes the ciliated respiratory epithelium of the nasopharynx, so the best sample comes from that site.
Step 3: A nasopharyngeal swab (or nasopharyngeal aspirate) collected from the posterior nasopharynx provides the highest yield for culture, PCR and direct fluorescent antibody testing.
Step 4: The cough plate method (holding a culture plate in front of the coughing child) is an old, low-yield technique and is not the best confirmatory test.
Step 5: Tracheal aspirate and oral swab are not the preferred sites because the organism does not concentrate there.
Conclusion: The nasopharyngeal swab is the best confirmatory specimen, so the printed key (A) is correct.