<prompt> A child presents with complaints of cough. Characteristic inspiratory whoop present. He is not immunised. Sample for investigation is:Nasopharyngeal swabTracheal aspirationCough plate cultureSputum culture  <response>: a. Nasopharyngeal swabRef: Nelsons 20e p 1377-1381, Ghai 8e p 242-243For diagnosis of Whooping cough isolation of B. pertussis in culture remains the gold standardThe specimen is obtained with deep nasopharyngeal aspiration or a swabCough plates and postnasal swabs are unsatisfactory because of overgrowth by commensal bacteriaDNA detection by PCR is replacing culture because of increased sensitivity quicker results. 