What is the optimal specimen type for recovering Bordetella pertussis?

• A. Anterior nares swab
• B. Blood
• C. Expectorated sputum
• D. Nasopharyngeal swab

Answer: (D)

Bordetella pertussis is most reliably recovered from the nasopharynx because this bacterium colonizes the mucosa there and is shed in that region early in the illness. A nasopharyngeal swab (or aspiration) from the posterior nasopharynx captures the highest bacterial load, making culture and PCR testing most sensitive. Anterior nares swabs sample a much smaller, more superficial area and miss many organisms; blood would not contain the organism, and expectorated sputum is uncommon in pertussis and can be contaminated and less reliable. Therefore, a nasopharyngeal specimen collected properly provides the best chance to detect Bordetella pertussis. Collecting the sample early in the disease course and before antibiotics further improves yield.