Pertussis and Diphtheria

A 6-month-old infant from rural Uttar Pradesh presents with a 3-week history of paroxysmal cough with inspiratory stridor and post-tussive vomiting. Nasopharyngeal swab culture on Bordet–Gengou medium grows gram-negative coccobacilli. Regarding pertussis, all of the following are true EXCEPT:

A 4-year-old child from Delhi presents with sore throat, low-grade fever, and a thick grayish-white pseudomembrane over the tonsils and pharynx. Gram stain shows gram-positive bacilli. Regarding diphtheria, all of the following statements are correct EXCEPT:

A 3-year-old unvaccinated child from a low-income urban settlement in Delhi presents with fever, sore throat, and a grayish-white pseudomembrane covering the tonsils and pharynx. Gram stain shows gram-positive bacilli. What is the most common site of diphtheria in this patient?

A 3-month-old male infant from rural Maharashtra presents with a 2-week history of paroxysmal cough followed by a characteristic high-pitched inspiratory sound. The mother reports the infant has not received any vaccinations. On examination, the child is afebrile, with copious nasal secretions and mild conjunctival injection. Chest examination reveals scattered crackles but no consolidation. A nasopharyngeal swab culture on Bordet-Gengou medium shows small, gram-negative coccobacilli. What is the most appropriate next step in management?

A 5-year-old unvaccinated girl from Uttar Pradesh presents with a 4-day history of sore throat, low-grade fever (38.2°C), and difficulty swallowing. On examination, she has a grayish-white pseudomembrane covering the tonsils and extending to the pharynx, with significant cervical lymphadenopathy and mild neck edema. The child appears lethargic. A throat swab is sent for culture. While awaiting culture results, which is the most appropriate immediate management?