Pneumonia USMLE Step 1 Practice Question
A 9-year-old boy presents to the emergency department with a 4-day history of fever, productive cough, and right-sided pleuritic chest pain. His mother reports he had symptoms of rhinitis and pharyngitis 1 week prior that were improving. On physical examination, temperature is 38.9°C, respiratory rate is 28/min, and heart rate is 110/min. Chest auscultation reveals decreased breath sounds and dullness to percussion in the right lower lobe. Laboratory studies show a positive rapid antigen detection test for Group A Streptococcus from a throat swab obtained 3 days ago. Chest X-ray demonstrates right lower lobe consolidation with a small parapneumonic pleural effusion. Which of the following organisms is most likely responsible for this patient's pneumonia?
Answer choices
- AHaemophilus influenzae type b
- BStaphylococcus aureus
- CGroup A StreptococcusCorrect answer
- DStreptococcus pneumoniae
- EMycoplasma pneumoniae
- FMoraxella catarrhalis
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.