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IM3.1-22 | Pneumonia — Practice Quiz
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A 55-year-old male farmer presents with three days of high fever, productive cough with rusty sputum, right-sided pleuritic chest pain, and herpes labialis. He has no recent hospitalisation. Examination shows dullness to percussion and bronchial breath sounds at the right lower zone. Which single organism is most likely responsible?
Correct. Streptococcus pneumoniae is the single most common cause of CAP in all age groups. The classic features — acute lobar consolidation, rusty sputum (altered haemoglobin from alveolar haemorrhage), pleuritic chest pain, and herpes labialis (reactivation with pneumococcal infection) — together point strongly to pneumococcal pneumonia. Community acquisition with no prior hospitalisation confirms CAP.
Pneumococcal CAP classic triad: acute fever + rusty sputum + pleuritic chest pain. Herpes labialis reactivation is a recognised associated finding. Community acquisition (no hospitalisation in prior 90 days) = CAP.
Streptococcus pneumoniae is the most frequent cause of CAP. The rusty sputum (from alveolar capillary haemorrhage) and herpes labialis reactivation are classic pointers. Klebsiella causes 'currant jelly' sputum in alcoholics; Legionella causes atypical pneumonia without classic consolidation signs; Mycoplasma causes a dry cough with minimal auscultatory findings.
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A 45-year-old man is admitted with CAP. His clinical data: confusion (new onset), urea 8.2 mmol/L, respiratory rate 26/min, BP 92/60 mmHg, age 45. What is his CURB-65 score, and what does it indicate for site of care?
Correct. CURB-65 scores 1 point each for: Confusion (new onset) — YES (1), Urea >7 mmol/L — YES (1), Respiratory rate ≥30/min — NO, rate is 26 (0), Blood pressure systolic <90 or diastolic ≤60 — YES (1), age ≥65 — NO (0). However, BP 92/60 = systolic 92 (not <90) and diastolic 60 (borderline — 60 is the cut-off, so ≤60 scores, and 60 qualifies). Re-scoring: C=1, U=1, R=0 (26 < 30), B=1 (diastolic 60 ≤60), age=0. Score = 3. CURB-65 3 = hospitalise + assess for ICU. Note: the question states BP 92/60 — systolic 92 ≥90 does NOT score for B; diastolic 60 ≤60 DOES score. Score = 3, not 4. Option B is therefore correct.
CURB-65: Confusion + Urea >7 mmol/L + RR ≥30/min + BP (systolic <90 OR diastolic ≤60) + age ≥65. Score 0-1 = outpatient; 2 = short-stay ward; 3-4 = hospital + consider ICU; 5 = ICU. Each criterion scores exactly 1 point.
CURB-65 components: C=new Confusion (1), U=Urea >7 mmol/L (1), R=RR ≥30/min (0 — RR is 26), B=BP systolic <90 OR diastolic ≤60 (1 — diastolic is 60 which equals the cut-off), 65=age ≥65 (0). Total = 3. CURB-65 3 indicates hospital admission with ICU assessment.
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A 32-year-old IT professional presents with two weeks of gradual onset dry cough, low-grade fever, headache, and mild myalgia. CXR shows bilateral patchy infiltrates disproportionate to the minimal auscultatory findings. Cold agglutinins are positive. Which antibiotic class is the treatment of choice?
Correct. The 'walking pneumonia' presentation — gradual onset, dry cough, bilateral patchy infiltrates disproportionate to clinical findings, positive cold agglutinins — is the hallmark of Mycoplasma pneumoniae atypical pneumonia. Mycoplasma lacks a cell wall and is therefore intrinsically resistant to all beta-lactams. Macrolides (azithromycin 500 mg day 1, then 250 mg days 2-5, or clarithromycin 500 mg BD for 7-10 days) are first-line. Doxycycline and respiratory fluoroquinolones are alternatives.
Atypical CAP pathogens (Mycoplasma, Chlamydophila, Legionella) lack a cell wall or are intracellular — beta-lactams are ineffective. Macrolides cover all three. Legionella: urinary antigen test; hyponatraemia + diarrhoea + high LDH are extra clues.
Mycoplasma pneumoniae has no cell wall — beta-lactams are therefore ineffective. The atypical presentation (gradual onset, dry cough, extrapulmonary features, bilateral patchy infiltrates, cold agglutinins) is the clinical fingerprint. Macrolides (azithromycin) are the treatment of choice for atypical CAP.
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A patient with known alcoholism presents with high fever, foul-smelling purulent sputum, and radiological evidence of a cavity with an air-fluid level in the right lower lobe. He aspirated vomit three days before admission. Blood culture grows Gram-negative rods. Which combination best describes this patient's pneumonia type and most likely causative organism?
Correct. This is aspiration pneumonia complicated by lung abscess. The setting (alcoholism), event (aspiration of vomit), dependent lobe involvement (right lower lobe is dependent in the supine/semi-recumbent position), foul-smelling sputum, and cavitation with air-fluid level on CXR are the classic features. Klebsiella pneumoniae is the most important Gram-negative pathogen in aspiration pneumonia in alcoholics — it characteristically causes cavitation and 'currant jelly' (blood-stained) sputum. Mixed anaerobes also cause aspiration pneumonia but do not grow on standard blood culture; Gram-negative rods on blood culture points to Klebsiella.
Aspiration pneumonia: right lower and middle lobe (upright) or right upper/lower posterior segment (supine). Causative organisms: mixed mouth anaerobes (community), Gram-negatives including Klebsiella in alcoholics. Cavitation = lung abscess — requires prolonged antibiotics (4-6 weeks) and sometimes drainage.
Aspiration in an alcoholic + right lower lobe + cavitation with air-fluid level + Gram-negative rods on blood culture = aspiration pneumonia complicated by lung abscess with Klebsiella. Klebsiella characteristically causes cavitation in aspiration pneumonia; mixed anaerobes are common in aspiration but rarely grow on blood culture.
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A 60-year-old man is on a mechanical ventilator in the ICU following elective surgery. On day 5 post-operation, his temperature rises to 39.2°C, WBC 18,000/mm3, CXR shows new bilateral infiltrates, and endotracheal secretions become purulent. Which single criterion correctly defines his condition?
Correct. VAP is defined as pneumonia occurring more than 48 hours after endotracheal intubation (or tracheostomy) in a patient on mechanical ventilation. It is a subset of HAP. The key defining feature is the presence of an artificial airway (endotracheal tube), which bypasses upper airway defences and allows direct inoculation of the lower respiratory tract with oropharyngeal flora. VAP has a distinct pathogen spectrum (often MDR organisms: MRSA, Pseudomonas, Acinetobacter, Enterobacterales) and higher mortality than non-ventilator HAP.
HAP: pneumonia ≥48 hours after admission, not intubated. VAP: pneumonia ≥48 hours after intubation. Both HAP and VAP: cover MDR organisms (Pseudomonas, MRSA, Acinetobacter, ESBL-producers). VAP diagnosis requires new radiological infiltrates + clinical criteria (fever, leukocytosis, purulent secretions).
VAP is specifically pneumonia in a mechanically ventilated patient, >48 hours after intubation. HAP is the broader category (any pneumonia >48 hours after admission in a non-intubated patient). VAP has different pathogens, worse prognosis, and specific management guidelines.
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You are examining a patient admitted with CAP. You percuss the right mid-zone and find dullness. On auscultation, you hear increased vocal resonance and whispering pectoriloquy over the same area. What does this combination of signs indicate, and what is its underlying mechanism?
Correct. Consolidation (alveoli filled with inflammatory exudate) makes the lung tissue solid, converting it from a poor sound conductor (normal air-filled lung) to an excellent conductor. Solid lung transmits sounds from the large airways directly to the chest wall, producing: increased vocal fremitus/resonance (voice sounds louder), whispering pectoriloquy (whispered sounds clearly audible), bronchial breath sounds (high-pitched, equal inspiration and expiration), and aegophony (E-to-A change). Dullness occurs because fluid-filled alveoli do not resonate. Pleural effusion gives dull percussion but decreased (not increased) vocal resonance.
Consolidation signs: dullness, increased vocal resonance, whispering pectoriloquy, aegophony, bronchial breath sounds, pleural rub if adjacent pleura involved. Effusion: dullness, decreased or absent breath sounds, decreased vocal resonance, stony dullness. The presence of increased vocal resonance differentiates consolidation from effusion.
Consolidation gives the complete triad: dull percussion + increased vocal resonance/whispering pectoriloquy + bronchial breath sounds. The mechanism is solid lung conducting sound better than air. Pleural effusion also gives dullness but reduces vocal resonance (fluid blocks transmission). This distinction is critical for the clinical diagnosis of pneumonia.
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A 48-year-old woman is admitted with CAP and a right-sided pleural effusion. You perform diagnostic thoracentesis. The pleural fluid results: appearance — cloudy, protein 48 g/L (serum protein 72 g/L), LDH 380 U/L (serum LDH 200 U/L), glucose 2.1 mmol/L, pH 7.1, Gram stain shows Gram-positive cocci in clusters. What is the correct classification and immediate management?
Correct. Light's criteria: Exudate if at least ONE of: pleural protein/serum protein >0.5 (48/72 = 0.67 — YES), pleural LDH/serum LDH >0.6 (380/200 = 1.9 — YES), pleural LDH >2/3 upper limit of normal (YES). This is an exudate. Further classification: pH <7.2, glucose <2.2 mmol/L, positive Gram stain = empyema (frank pus or positive microbiology). Empyema requires chest tube drainage in addition to antibiotics. Antibiotics alone cannot sterilise an empyema. MRSA (Gram-positive cocci in clusters) — cover with vancomycin.
Pleural fluid classification: Exudate (Light's criteria: protein ratio >0.5, LDH ratio >0.6, LDH >2/3 ULN). Parapneumonic effusion management: simple (pH >7.2, glucose normal, Gram stain negative) = antibiotics; complicated (pH 7.0-7.2) or empyema (pH <7.0, positive microbiology) = drain. Empyema always requires tube drainage.
Light's criteria establish this as an exudate. Low pH (<7.2), low glucose (<2.2 mmol/L), and positive Gram stain confirm empyema, not simple parapneumonic effusion. Empyema mandates chest tube drainage — antibiotics alone are insufficient because the fluid is infected and cannot be cleared without drainage.
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A 68-year-old woman is admitted with severe CAP (CURB-65 = 3). ABG on room air shows: pH 7.32, PaO2 52 mmHg, PaCO2 35 mmHg, HCO3 18 mEq/L. SpO2 83%. Which is the most appropriate immediate management of her hypoxaemia?
Correct. This patient has type 1 respiratory failure (hypoxaemia with low PaCO2 — she is hyperventilating to compensate). SpO2 of 83% is dangerous. In non-COPD patients with pneumonia, the target SpO2 is 94-98%, achieved with supplemental oxygen via face mask or high-flow nasal cannula. PaCO2 is 35 mmHg (not elevated), so there is no risk of hypercapnic drive suppression from high-flow oxygen. Controlled low-flow oxygen is reserved for COPD patients with type 2 failure (elevated PaCO2). NIV and intubation are escalation options if oxygen alone fails — not the immediate first step.
Oxygen targets in pneumonia: non-COPD SpO2 94-98%; COPD/at-risk-of-hypercapnia SpO2 88-92%. Type 1 RF: hypoxaemia + PaCO2 normal or low (hyperventilation). Type 2 RF: hypoxaemia + elevated PaCO2. Indications for NIV: type 2 RF with pH <7.35. Indications for intubation: failing NIV, obtunded, unable to protect airway.
Type 1 respiratory failure (low PaO2, low/normal PaCO2) in a non-COPD patient requires supplemental oxygen to target SpO2 94-98%. High-flow oxygen is safe here — there is no hypercapnic risk. Controlled low-dose oxygen (Venturi) is for COPD with CO2 retention. NIV/intubation are escalation steps if high-flow oxygen fails.
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A 58-year-old man with no comorbidities is diagnosed with mild outpatient CAP (CURB-65 = 1). Chest X-ray shows lobar consolidation. He has no penicillin allergy. What is the most appropriate empirical antibiotic regimen for outpatient management?
Correct. For mild outpatient CAP (CURB-65 0-1) in a patient without significant comorbidities, oral amoxicillin 500 mg TID for 5-7 days is the recommended first-line empirical regimen in Indian and UK-NICE guidelines, as it covers Streptococcus pneumoniae (the most common CAP pathogen) effectively. If atypical pathogen cover is also needed (e.g., suspected Mycoplasma), add a macrolide. IV antibiotics are unnecessary for mild outpatient disease. Ciprofloxacin lacks reliable pneumococcal cover and should not be used as monotherapy for CAP.
CAP empirical regimens: Outpatient mild (CURB-65 0-1): oral amoxicillin ± macrolide (add macrolide if atypical suspected). Inpatient non-ICU (CURB-65 2-3): IV ceftriaxone + IV azithromycin. ICU/severe (CURB-65 4-5): IV beta-lactam + IV macrolide or respiratory fluoroquinolone. HAP/VAP: antipseudomonal beta-lactam ± anti-MRSA (vancomycin/linezolid).
Mild CAP (CURB-65 0-1) managed outpatient: oral amoxicillin is the first choice in most Indian/international guidelines. IV therapy is inappropriate for outpatient mild CAP. Ciprofloxacin does not adequately cover Streptococcus pneumoniae. Macrolides are added if atypical pathogens are suspected.
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A 42-year-old HIV-positive man (CD4 count 85 cells/mm3) presents with progressive breathlessness over 3 weeks, dry cough, and mild fever. CXR shows bilateral diffuse perihilar haziness ('butterfly' pattern). SpO2 is 88% on room air. Silver-stain of induced sputum is positive for cysts. What is the most likely diagnosis and first-line treatment?
Correct. Pneumocystis jirovecii pneumonia (PCP) is the classic AIDS-defining opportunistic infection at CD4 <200 cells/mm3. Features: subacute onset (weeks), dry cough, hypoxaemia disproportionate to CXR findings, bilateral perihilar/interstitial infiltrates, positive silver stain (methenamine silver stains cysts). First-line: high-dose co-trimoxazole (TMP 15-20 mg/kg/day + SMX 75-100 mg/kg/day) divided 6-8 hourly for 21 days. Add prednisolone if PaO2 <70 mmHg or A-a gradient >35 mmHg. PCP prophylaxis (low-dose TMP-SMX) when CD4 <200.
Opportunistic pneumonias by CD4 count: CD4 <500 — bacterial (S. pneumoniae); CD4 <200 — PCP (silver stain +, TMP-SMX); CD4 <100 — Toxoplasma, Cryptococcus; CD4 <50 — CMV, MAC. HIV testing is mandatory in any unexplained pneumonia with risk factors or atypical pattern (NACO guidelines).
PCP at CD4 <200: subacute onset, dry cough, hypoxaemia disproportionate to CXR, bilateral perihilar infiltrates, positive silver stain. Treatment: high-dose co-trimoxazole for 21 days + steroids if severe hypoxaemia. NTEP regimen is for tuberculosis (acid-fast bacilli, not cysts on silver stain).
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