A 35-year-old man comes to the emergency department with fever, chills, dyspnea, and a productive cough. His symptoms began suddenly 2 days ago. The patient has no prior medical conditions and does not use tobacco, alcohol, or illicit drugs He lives in Illinois and works as a carpenter. His temperature is 38.8°C (101.8°F), pulse is 110/min, respirations are 24/min, and blood pressure is 105/74 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 92%. Examination reveals crackles over the right lower lung base. The remainder of the examination shows no abnormalities. An x-ray of the chest shows a right lower-lobe infiltrate of the lung. The underlying immune response to this patient's infection largely involves T helper (Th1) cells, interferon-gamma, and interleukin-2. Which of the following is the most likely pathogen responsible for this patient's pneumonia?

Question

A 35-year-old man comes to the emergency department with fever, chills, dyspnea, and a productive cough. His symptoms began suddenly 2 days ago. The patient has no prior medical conditions and does not use tobacco, alcohol, or illicit drugs He lives in Illinois and works as a carpenter. His temperature is 38.8°C (101.8°F), pulse is 110/min, respirations are 24/min, and blood pressure is 105/74 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 92%. Examination reveals crackles over the right lower lung base. The remainder of the examination shows no abnormalities. An x-ray of the chest shows a right lower-lobe infiltrate of the lung. The underlying immune response to this patient's infection largely involves T helper (Th1) cells, interferon-gamma, and interleukin-2.  Which of the following is the most likely pathogen responsible for this patient's pneumonia?

Quizplus · Accepted Answer

Eductional Objective: Intracellular bacterial organisms such as Legionella pneumophila are primarily countered by the cell-mediated immune response.  Intracellular pathogens that replicate within phagosomes (eg, Legionella, Mycobacterium tuberculosis) trigger activation and differentiation of T-helper subtype 1 cells with subsequent macrophage activation via interferon-gamma.

A 35-Year-Old Man Comes to the Emergency Department with Fever