A 6-month-old female infant from Delhi presents with a 3-day history of progressive respiratory distress, stridor, and low-grade fever. On examination, she is in severe respiratory distress with inspiratory stridor, drooling, and tripoding. Lateral neck X-ray shows subglottic narrowing with a 'church steeple' appearance. Direct laryngoscopy is contraindicated due to risk of complete airway obstruction. Blood culture is sent. What is the most likely causative organism and what is the immediate management priority?