Right Middle Lobe Pneumonia MCQ — NEET PG Practice Question | NEETPGAI
Right Middle Lobe Pneumonia
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stethoscope Medicine
A 58-year-old man presents with a 4-day history of productive cough, fever, and dyspnea. Chest X-ray shows right middle lobe consolidation with loss of the right heart border. High-resolution CT confirms lobar consolidation. The structure marked **B** in the diagram—air bronchograms within the consolidation—is a characteristic finding. Which of the following is the MOST COMMON bacterial pathogen responsible for this presentation?
A. Haemophilus influenzae (typically associated with COPD exacerbation)
B. Staphylococcus aureus (post-influenza, cavitating pneumonia)
C. Klebsiella pneumoniae (associated with alcoholism and currant-jelly sputum)
D. Streptococcus pneumoniae (Gram-positive diplococci, alpha-haemolytic, optochin-sensitive)
Explanation
Why Streptococcus pneumoniae is right
Streptococcus pneumoniae is the most common bacterial pathogen in community-acquired pneumonia (CAP) across all age groups and risk strata, as per IDSA/ATS guidelines 2019. The presence of air bronchograms—branching tubular lucencies representing patent airways within fluid- or pus-filled alveoli—is a hallmark radiological sign of bacterial pneumonia, particularly pneumococcal infection. The organism is a Gram-positive diplococci, alpha-haemolytic on blood agar, and optochin-sensitive, making it readily identifiable in culture.
Why each distractor is wrong
Haemophilus influenzae: While an important CAP pathogen, it is classically associated with COPD exacerbation and is NOT the most common cause of CAP in the general population. It is a Gram-negative coccobacillus, not a diplococci.
Staphylococcus aureus: This is a secondary pathogen, typically following influenza infection or in healthcare-associated settings. It is known for cavitating pneumonia and abscess formation, not the classic air bronchogram pattern seen here. It is Gram-positive but in clusters, not diplococci.
Klebsiella pneumoniae: This Gram-negative rod is associated with alcoholism, aspiration, and the characteristic "currant-jelly" sputum and bulging fissure sign. It is NOT the most common cause of uncomplicated CAP in a non-alcoholic patient.
High-YieldNEET PG
Streptococcus pneumoniae is the #1 CAP pathogen; air bronchograms indicate patent airways within consolidated alveoli—a classic finding in bacterial pneumonia.
