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Pneumonia - Complete Clinical Guide

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1. HISTORY POINTS

Presenting Symptoms

• Cough - productive of purulent, rust-colored (pneumococcal), blood-streaked (streptococcal/TB), or currant jelly sputum (Klebsiella)
• Fever and chills - abrupt single shaking chill strongly suggests pneumococcal pneumonia
• Dyspnea / shortness of breath
• Pleuritic chest pain - sharp, worsened by breathing; suggests lobar pneumonia
• Hemoptysis - raises concern for MRSA, TB, or malignancy

Associated Symptoms to Ask About

• Headache, malaise, myalgias - viral prodrome or Mycoplasma
• Diarrhea + confusion + hyponatremia - classic for Legionella
• Non-productive cough + gradual onset + younger patient - Mycoplasma ("walking pneumonia")
• Confusion or acute change in mental status - especially in elderly; may be the only presenting symptom
• Abdominal or back pain - lower lobe pneumonia can present this way

Epidemiological History (Critical)

• Setting of acquisition: community-acquired (CAP), healthcare-associated, hospital-acquired, or ventilator-associated
• Recent hospitalization or long-term care facility (risk for resistant organisms: Klebsiella, Pseudomonas, MRSA)
• Geographic exposures: travel to endemic areas (histoplasmosis - Mississippi Valley; coccidioidomycosis - American Southwest)
• Animal exposures: birds (Chlamydophila psittaci), farm animals (Coxiella burnetii - Q fever), bats (histoplasma)
• Recent influenza illness - raises strong suspicion for secondary S. aureus/MRSA pneumonia

Host Factors (Risk History)

• Asplenia, sickle cell disease, HIV, multiple myeloma, agammaglobulinemia - increased risk of pneumococcal bacteremia
• COPD - colonized with S. pneumoniae, H. influenzae, Moraxella catarrhalis
• Cystic fibrosis - prone to Pseudomonas and S. aureus
• Immunosuppression (chemotherapy, transplant, HIV with CD4 <200) - adds CMV, PCP (P. jirovecii), Aspergillus, Cryptococcus
• IV drug use, alcoholism, undomiciled status - raises TB risk
• Recent antibiotic use (in last 3 months) - raises likelihood of drug-resistant organisms
• Swallowing dysfunction, impaired consciousness - aspiration risk

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2. CLINICAL FEATURES (Examination)

Typical Pneumonia (Pyogenic Bacteria - e.g., S. pneumoniae)

• High fever (>38.5°C), tachycardia, tachypnoea
• Signs of consolidation: dullness to percussion, bronchial breathing, increased tactile fremitus
• Crackles (crepitations) over involved area
• Bronchophony, egophony, whispered pectoriloquy - (note: poor inter-rater reliability despite being "classic")
• Pleural rub if pleuritis is present

Atypical Pneumonia (Mycoplasma, Chlamydophila, Legionella)

• More gradual, "flu-like" onset
• Non-productive cough, lower degree of fever
• Absence of rigors, absent consolidation signs
• Extra-pulmonary features: rash (erythema multiforme in Mycoplasma), bullous myringitis, diarrhea (Legionella)
• Patient appears less toxic despite abnormal CXR

Important: The "typical vs atypical" distinction cannot reliably differentiate pathogens on clinical grounds alone and does NOT reliably guide treatment decisions. - Rosen's Emergency Medicine 9e

In Elderly / Debilitated Patients

• Classic symptoms may be absent
• May present with only acute confusion, functional decline, or sepsis without a clear respiratory syndrome
• More likely to have advanced disease at presentation

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3. INVESTIGATIONS

Chest Imaging

• Lobar consolidation + air bronchograms - typical pyogenic bacteria (S. pneumoniae, Klebsiella)
• Patchy/segmental infiltrates (bronchopneumonia) - S. pyogenes, Mycoplasma, viruses
• Dense lobar consolidate with bulging fissure ("lobar expansion") - classically Klebsiella
• Bilateral interstitial infiltrates - PCP, viral pneumonia
• Cavitation - Staphylococcus, Klebsiella, TB, anaerobes, MRSA
• Pleural effusion - common in pyogenic bacteria, Legionella, TB

Blood Tests

• FBC (CBC) - WBC >15,000/mm³ suggests pyogenic bacterial cause; normal WBC more common with atypical/viral
• CRP, Procalcitonin - elevated in bacterial pneumonia; procalcitonin can help guide antibiotic duration
• Blood cultures - low yield (~5.8%) in immunocompetent outpatients; recommended for severe disease, ICU patients, suspected resistant organisms, or prior to antibiotics
• LFTs, U&E, Creatinine - for severity scoring and organ dysfunction
• Arterial Blood Gas (ABG) - if SpO2 <94% or severe disease; assess hypoxemia, hypocapnia (seen in PCP)
• LDH - elevated in PCP pneumonia; useful in HIV patients

Microbiology

• Sputum Gram stain + culture - recommended for severe disease or if resistant pathogens are suspected; requires <10 squamous epithelial cells and >25 WBCs per high-power field for an adequate specimen; obtain BEFORE antibiotics
• Urinary antigen tests:
  • Legionella pneumophila serogroup 1 - sensitivity ~74%, specificity ~99%
  • S. pneumoniae - sensitivity ~74%, specificity ~96%
• PCR/Multiplex panel (e.g., BioFire) - rapidly identifies bacteria and viruses; not affected by prior antibiotics; especially useful in outbreak settings
• Serology - C. pneumoniae, Legionella, fungi; useful retrospectively with paired titres, limited acute utility

Severity Scoring

• Score 0-1: Outpatient treatment
• Score 2: Consider hospital admission
• Score ≥3: Hospitalize; consider ICU

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4. TREATMENT

Site of Care Decision

Outpatient Treatment (CAP)

Macrolide monotherapy is no longer recommended unless local pneumococcal resistance is <25%.

Inpatient (Non-ICU)

• Beta-lactam (ceftriaxone 1-2g IV daily) + macrolide (azithromycin)
• OR respiratory fluoroquinolone monotherapy (levofloxacin 750mg IV/PO daily)

ICU / Severe CAP

• Beta-lactam + macrolide (preferred combination)
• OR beta-lactam + respiratory fluoroquinolone
• Consider MRSA coverage (vancomycin, linezolid, ceftaroline) if: necrotizing pneumonia, preceding influenza, known MRSA contact, severe sepsis in young healthy adult

Special Pathogens

• Legionella: fluoroquinolone or azithromycin
• PCP (HIV/immunocompromised): TMP-SMX (co-trimoxazole) + corticosteroids if PaO2 <70 mmHg
• Aspiration pneumonia: only treat with antibiotics if signs of secondary bacterial infection develop >36 hours later; avoid prophylactic antibiotics

Duration

• Outpatient CAP: 5-7 days
• Hospitalized CAP: 5-7 days; no less than 5 days; can step down to oral once stable
• Reassess if no improvement in 48-72 hours

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5. COMPLICATIONS

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6. DIFFERENTIAL DIAGNOSIS - AND HOW TO DIFFERENTIATE

A. Pulmonary Tuberculosis (TB)

Always consider TB in any patient with HIV and respiratory complaints, and place them in respiratory isolation.

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B. Congestive Heart Failure (CHF) - Acute Pulmonary Edema

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C. Pulmonary Embolism (PE)

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D. Aspiration Pneumonitis vs Aspiration Pneumonia

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E. Lung Cancer (or Post-obstructive Pneumonia)

Any pneumonia that fails to resolve on CXR after 6 weeks should prompt CT chest to rule out underlying malignancy.

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F. Sarcoidosis / Hypersensitivity Pneumonitis

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Quick Memory Summary

PNEUMONIA
├── History: Cough + Fever + Purulent sputum + Pleuritic pain
│   Ask: Setting (CAP/HAP), Epidemiology, Host factors, Prodrome
├── Exam: Consolidation signs - Dull, ↑ Fremitus, Bronchial breath
├── Investigations:
│   ├── CXR (consolidation/infiltrate)
│   ├── FBC, U&E, CRP, Cultures
│   ├── Urine antigens (Legionella + Pneumococcal)
│   └── Severity: CURB-65
├── Treatment:
│   ├── Outpatient: Amoxicillin ± Doxycycline
│   ├── Inpatient: Ceftriaxone + Azithromycin (or Levofloxacin)
│   └── ICU: Add MRSA cover if indicated
├── Complications:
│   Effusion → Empyema → Abscess → Bacteremia → ARDS → MOF
└── Differentials:
    TB (subacute, upper lobe, night sweats)
    CHF (cardiomegaly, bat-wing, elevated BNP)
    PE (sudden, no fever, CTPA)
    Aspiration (timing, risk factors)
    Cancer (non-resolving infiltrate at 6 weeks)

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