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Pneumonia: Clinical Features & Advanced Management for the Medicine Resident

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1. Classification

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2. Epidemiologic Clues to Etiology

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3. Clinical Features

Symptoms

• Typical CAP (bacterial): abrupt-onset chills and fever, productive cough (purulent/blood-tinged), pleuritic chest pain, dyspnea, possible septic shock presentation. Elevated or depressed WBC with band forms, dense lobar/segmental consolidation, PCT ≥0.25 μg/L.
• Atypical CAP (Mycoplasma, Chlamydia, Legionella): stable cough lasting >5 days, non-productive cough, gradual onset, extrapulmonary features (headache, myalgias, diarrhea, confusion), mild or normal leukocytosis, PCT ≤0.1 μg/L, diffuse bilateral/interstitial pattern.
• Gross hemoptysis - raises concern for necrotizing pneumonia (CA-MRSA, P. aeruginosa, Klebsiella).
• Up to 20% have GI symptoms (nausea, vomiting, diarrhea) - classically Legionella.
• Elderly - may present with only new confusion or worsening chronic illness with minimal respiratory symptoms.

Physical Examination

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4. Diagnosis

Chest Imaging

• CXR is the standard for confirming pneumonia (new infiltrate required). Radiographic findings may lag clinical improvement by 4-6 weeks.
• Multilobar involvement, rapid expansion, or cavitation signal higher severity.
• Lung ultrasound (LUS): The 2026 ATS CAP guideline now conditionally recommends LUS as an alternative to CXR for initial diagnosis in resource-appropriate settings (PMID 40679934). B-lines, subpleural consolidation, and air bronchograms are the key sonographic findings.
• CT chest: Use when CXR is inconclusive, suspecting necrotizing pneumonia, abscess, empyema, or when the patient is not responding to treatment.

Microbiologic Workup

• Sputum Gram stain and culture (before antibiotics if possible)
• Blood cultures x2 (before antibiotics; yield ~5-14%)
• Urinary antigen for S. pneumoniae (sensitivity ~70-80%)
• Urinary antigen for Legionella (sensitivity ~75% for serogroup 1)
• Influenza PCR/rapid antigen (seasonal)
• SARS-CoV-2 testing

• Sputum/BAL for Gram stain, culture, and sensitivity
• Respiratory viral panel (multiplex PCR)
• Legionella sputum PCR and culture on selective media
• Serum procalcitonin (PCT) and CRP
• HIV testing if risk factors or age <50 with unexplained immunodeficiency
• Consider bronchoscopy if no diagnosis after standard workup

• Supports bacterial vs. viral distinction, but do not withhold antibiotics based on PCT alone in radiographically-confirmed pneumonia (strong IDSA/ATS recommendation).
• Atypical pathogens (Mycoplasma, Chlamydia) do not reliably elevate PCT.
• PCT is most useful for antibiotic de-escalation/duration decisions in stable patients.

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5. Severity Scoring and Site-of-Care Decisions

PSI (Pneumonia Severity Index / PORT Score)

• 20 variables: age, comorbidities, vital signs, labs, CXR findings
• Class I-II: outpatient; Class III: borderline (short observation or admit); Class IV-V: hospital/ICU
• More validated and mortality-specific, but complex for bedside use.

CURB-65

IDSA/ATS Minor Criteria for Severe CAP (ICU Admission)

RR ≥30, PaO2/FiO2 <250, multilobar infiltrates, confusion/disorientation, BUN ≥20 mg/dL, WBC <4000 cells/mm3, platelets <100,000/mm3, temperature <36°C, hypotension requiring aggressive IV fluid resuscitation.

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6. Antibiotic Management

Outpatient CAP (no comorbidities, no recent antibiotics)

• Amoxicillin 1 g PO TID, or
• Doxycycline 100 mg PO BID, or
• Macrolide (azithromycin) - only if local macrolide resistance in S. pneumoniae <25%

Outpatient CAP (comorbidities: COPD, diabetes, heart/liver/renal disease, asplenia, immunosuppression, or recent antibiotics)

• Respiratory fluoroquinolone (levofloxacin 750 mg OD or moxifloxacin 400 mg OD), or
• Amoxicillin-clavulanate + macrolide (amoxicillin-clavulanate preferred over amoxicillin alone due to β-lactamase-producing H. influenzae and M. catarrhalis)

Non-ICU Inpatient CAP

• β-lactam + macrolide: ceftriaxone 1-2 g IV OD + azithromycin 500 mg IV/PO OD (preferred combination), or
• Respiratory fluoroquinolone monotherapy: levofloxacin 750 mg IV/PO OD or moxifloxacin 400 mg IV/PO OD

ICU/Severe CAP (no Pseudomonas risk)

• β-lactam + azithromycin or
• β-lactam + respiratory fluoroquinolone

ICU CAP with Pseudomonas risk factors (bronchiectasis, cystic fibrosis, severe COPD, prior Pseudomonas isolation)

• Anti-pseudomonal β-lactam (piperacillin-tazobactam, cefepime, or imipenem/meropenem) + ciprofloxacin or levofloxacin, or
• Anti-pseudomonal β-lactam + aminoglycoside + azithromycin/respiratory FQ

MRSA Coverage (add when suspected: necrotizing/cavitating pneumonia, severe influenza, skin MRSA, failing standard therapy)

• Add vancomycin (15 mg/kg IV q8-12h, target trough 15-20 or AUC/MIC 400-600) or linezolid 600 mg IV/PO q12h
• Linezolid may be preferred for lung-tissue penetration in necrotizing MRSA pneumonia.

Antibiotic Duration

• 5 days: standard uncomplicated CAP (per 2026 ATS guideline recommendation - PMID 40679934)
• Extend to 7 days for non-responders, bacteremia, cavitation, or virulent pathogens (P. aeruginosa, MRSA).
• Clinical stability criteria guide de-escalation to oral therapy: afebrile, HR <100, RR <24, SBP ≥90, SpO2 ≥90% on room air, tolerating oral intake.

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7. Adjunctive and Advanced Management

Corticosteroids in Severe CAP

• Indicated in severe CAP requiring mechanical ventilation (invasive or non-invasive) or with septic shock (Harrison's 2025).
• Especially if systemic inflammation is high: CRP >150 mg/L.
• Regimen: Dexamethasone 6 mg/day IV (or methylprednisolone 0.5 mg/kg/day) for 8-14 days (by intermittent or continuous infusion).
• The 2026 ATS guideline also conditionally recommends corticosteroids in hospitalized CAP patients (PMID 40679934).
• Caution: avoid if influenza is the primary pathogen (risk of secondary bacterial infection worsening).

Oxygenation Targets

• Maintain SpO2 ≥92-94% (88-92% in COPD).
• High-flow nasal cannula (HFNC): First-line NIV for hypoxemic respiratory failure in CAP; reduces intubation rate compared to conventional O2.
• NIV (CPAP/BiPAP): Use in hypercapnic respiratory failure or as a bridge in cardiogenic pulmonary edema co-existing with CAP. Less benefit than HFNC for pure hypoxemic CAP.
• Intubation: If worsening despite HFNC, persistent PaO2/FiO2 <150, labored breathing, altered consciousness.

VAP Prevention Bundle (for intubated patients)

1. Head of bed elevation 30-45°
2. Subglottic secretion drainage ETT
3. Daily sedation interruption ("wake-up and breathe" trial)
4. Chlorhexidine oral decongestant
5. Minimize unnecessary antibiotic use (stewardship)

Antibiotic Stewardship Principles

• De-escalate empiric therapy once culture/sensitivity results are available.
• Switch to oral antibiotics once clinical stability criteria are met (typically day 2-3).
• Use PCT-guided protocols to support early discontinuation in stable patients.
• Target 5 days for uncomplicated CAP; avoid extending without clear clinical indication.

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8. Complications and Non-Response

Complications to Monitor

Causes of Treatment Failure (Reassess at Day 3)

1. Wrong organism - resistant pathogen, atypical not covered, TB, endemic fungus, CA-MRSA
2. Wrong drug - inadequate dose, drug interaction, poor absorption
3. Sequestered infection - empyema, lung abscess blocking antibiotic access
4. Non-infectious mimic - PE, pulmonary edema, malignancy, eosinophilic pneumonia, organizing pneumonia, vasculitis
5. Nosocomial superinfection - new hospital-acquired infection on top of CAP

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9. Special Populations

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10. Prevention

• PCV20/PCV15 + PPSV23 (pneumococcal vaccines) for adults ≥65 and high-risk younger adults
• Annual influenza vaccine for all adults
• Smoking cessation - significantly reduces H. influenzae, M. catarrhalis, S. pneumoniae risk
• COVID-19 vaccination (for SARS-CoV-2 related pneumonia prevention)

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2026 Update

1. Lung ultrasound as an acceptable diagnostic alternative to CXR
2. Antibacterial therapy even when respiratory virus is positive (conditional recommendation - bacterial co-infection is common, especially in severe illness)
3. 5-day antibiotic duration preferred for most CAP
4. Systemic corticosteroids conditionally recommended in hospitalized patients with severe inflammation

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