A 73-year-old man from a nursing home develops headache, fever, cough, sore throat, malaise, and severe myalgia during a community outbreak affecting numerous other residents at the home. The symptoms gradually resolve after 3 days, and he starts feeling better but then there is a reappearance of his fever, with cough and yellow sputum production. On examination, his temperature is 38.5degC, pulse 100/min, respiration 24/min, oxygen saturation 88% and crackles in the right lower lung base, bronchial breath sounds and dullness on percussion. CXR reveals a new infiltrate in the right lower lobe. Which of the following is the most likely causative organism?
High-Yield Explanation
This man has a complication of viral influenza; a secondary bacterial pneumonia has developed. This usually occurs 2-3 days after the initial viral symptoms resolve. Primary viral pneumonia with influenza is not common. Spneumoniae, Staphylococcus, and H influenzae are the most common bacterial invaders in pulmonary complications of influenza. Pneumonia is the leading cause of death and may also be due to Spneumoniae and H influenzae. Mixed viral and bacterial pneumonia is common; pure viral pneumonia in influenza is uncommon (but can be very severe).