Question:medium
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 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?
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Sample the site where Bordetella pertussis actually colonizes.
Updated On: Jun 24, 2026
- Nasopharyngeal swab
- Cough plate culture
- Tracheal aspirate
- Oral swab
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The Correct Option is A
Solution and Explanation
Match the suspected organism to the body site where it lives, then pick the sampling method that reaches that site.
The clinical story of repeated coughing fits that finish with a whoop in a baby whose vaccination is uncertain points firmly to $Bordetella$ $pertussis$. This bacterium has a strong preference for the ciliated lining of the nasopharynx, where it attaches and multiplies. To recover it reliably you must sample exactly there.
A swab passed to the posterior nasopharynx collects the organism at its main reservoir and can be sent for culture, PCR, or direct fluorescent antibody testing, giving the best diagnostic yield. The old cough plate technique, where a plate is held before the child's mouth during a coughing bout, captures far fewer organisms and is no longer recommended as the test of choice. A tracheal aspirate samples lower down where the bacterium is sparse, and a plain oral swab misses the nasopharyngeal niche entirely.
Therefore the best confirmatory specimen is a nasopharyngeal swab.
\[\boxed{\text{Nasopharyngeal swab}}\]
The clinical story of repeated coughing fits that finish with a whoop in a baby whose vaccination is uncertain points firmly to $Bordetella$ $pertussis$. This bacterium has a strong preference for the ciliated lining of the nasopharynx, where it attaches and multiplies. To recover it reliably you must sample exactly there.
A swab passed to the posterior nasopharynx collects the organism at its main reservoir and can be sent for culture, PCR, or direct fluorescent antibody testing, giving the best diagnostic yield. The old cough plate technique, where a plate is held before the child's mouth during a coughing bout, captures far fewer organisms and is no longer recommended as the test of choice. A tracheal aspirate samples lower down where the bacterium is sparse, and a plain oral swab misses the nasopharyngeal niche entirely.
Therefore the best confirmatory specimen is a nasopharyngeal swab.
\[\boxed{\text{Nasopharyngeal swab}}\]
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