This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Considerations - Infectious Diseases, Subject name: Pediatrics
[{'content': 'A child presents with complaints of cough. Characteristic inspiratory whoop present. He is not immunised. Sample for investigation is: \nSelect and explain. \nA. Nasopharyngeal swab, B. Tracheal aspiration, C. Cough plate culture, D. Sputum culture', 'role': 'user'}, {'content': "Answer: A \nExplanation: a. Nasopharyngeal swab(Ref: Nelson's 20/e p 1377-1381, Ghai 8/e p 242-243)For 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.", 'role': 'assistant'}]