A 3 mоnth оld infаnt presented with persistent symptоms thаt include pаroxysmal cough, breathing difficulty, fever and vomiting after a spasm of coughing. Cyanosis (lack of oxygen causing blue skin coloration) and intercostal retractions were noted. The infant also had a temperature. Nasophyrngeal secretions were collected and analyzed. The image below shows the colonies recovered after 5 days from the selective medium. The organism is biochemically inert. Based on this information, the suspected agent is most likely B pertussis colonies mercury drops.jpg