Pneumonia treatment

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Pneumonia Treatment

Pneumonia is classified by acquisition setting (community-acquired vs. hospital/healthcare-associated), and treatment is driven by this classification, the likely causative organisms, severity, and patient-specific risk factors.

1. Community-Acquired Pneumonia (CAP)

Likely Pathogens

Most common bacterial cause: Streptococcus pneumoniae (pneumococcus)
Atypical agents: Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella
Viral: influenza, RSV (especially in children)

Outpatient (Mild CAP)

Patient	First-line
Previously healthy, no recent antibiotics	Amoxicillin (high-dose) or macrolide (azithromycin, clarithromycin)
Comorbidities (COPD, DM, heart/liver/renal disease)	Respiratory fluoroquinolone (levofloxacin, moxifloxacin) or β-lactam + macrolide
Suspected atypical (Mycoplasma, Chlamydophila)	Macrolide monotherapy

Note: Macrolide resistance in pneumococci is a growing concern; amoxicillin ± clavulanate is preferred in many guidelines for children ≥3 months with simple CAP. — Tintinalli's Emergency Medicine, p. 857

Inpatient (Non-ICU)

β-lactam + macrolide (e.g., ceftriaxone + azithromycin)
or respiratory fluoroquinolone monotherapy (levofloxacin)

ICU / Severe CAP

β-lactam + macrolide or β-lactam + respiratory fluoroquinolone
Add MRSA coverage (vancomycin or linezolid) if risk factors present (cavitary lesion, post-influenza, prior MRSA)

Duration

Typically 5–7 days for outpatient CAP
7–10 days for most cases; 5 days if azithromycin is used
Some evidence supports 3–5 days in mild outpatient cases — Tintinalli's Emergency Medicine, p. 857

2. Hospital-Acquired Pneumonia (HAP) & Ventilator-Associated Pneumonia (VAP)

Key Principles

Antibiotics may be withheld in clinically stable patients until diagnosis is confirmed
Immediate treatment is mandatory in unstable patients (rapid hypoxemia or hypotension) — Goldman-Cecil Medicine, p. 1001

Empirical Regimen

Treatment targets MRSA + Pseudomonas aeruginosa + other gram-negatives:

Coverage	Agent Options
MRSA	Vancomycin or linezolid
Pseudomonas / GNR	Cefepime, ceftazidime, piperacillin-tazobactam, imipenem, meropenem, ciprofloxacin, levofloxacin, aztreonam
MDR / carbapenem-resistant	Ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-relebactam, cefiderocol, colistin

MRSA coverage can be de-escalated if:

Nasal swab or BAL PCR is MRSA-negative
No prior history of drug-resistant organisms
Hospital MRSA prevalence <20% of S. aureus isolates

Regimen must be tailored to individual risk factors (IV antibiotics in prior 90 days, prior resistant organism) and local antibiogram. — Goldman-Cecil Medicine, p. 1001

Common HAP Pathogens

Staphylococcus aureus (MRSA or MSSA) — 15–20%
Klebsiella spp. — ~10%
Enterobacter spp. — 5–10%
E. coli — 5–10%
Haemophilus influenzae — ~5%
Pseudomonas aeruginosa, Acinetobacter — variable
Respiratory viruses account for 20–25% of HAP

3. Pediatric Pneumonia Treatment

Age Group	Regimen
Neonates (<1 month)	Ampicillin + gentamicin or cefotaxime (covers group B Strep, Listeria, gram-negatives; ceftriaxone contraindicated due to bilirubin displacement)
1–3 months	Macrolide (erythromycin or clarithromycin) for atypical pathogens; azithromycin avoided (risk of pyloric stenosis)
3 months–5 years	High-dose oral amoxicillin (80–100 mg/kg/day); third-generation cephalosporin if high-resistance community or severe disease
5–18 years	Amoxicillin ± clavulanate (preferred); macrolide if atypical pneumonia strongly suspected; β-lactam + macrolide for hospitalized patients

Parenteral therapy is usually limited to neonates and those with severe pneumonia requiring hospitalization. — Tintinalli's Emergency Medicine, p. 857

4. Supportive Care (All Types)

Supplemental O₂: maintain SpO₂ >90–92%
Fluid management: IV or oral hydration for respiratory losses
Antipyretics: for comfort and fever reduction
Bronchodilators: for wheeze in asthmatic patients (not routinely in infants <24 months if bronchiolitis suspected)
Cough suppressants: not routinely indicated in children; avoid codeine (respiratory suppression risk)
Corticosteroids: hydrocortisone studied in severe CAP; not yet standard of care

5. Antibiotic Stewardship

Use procalcitonin-guided therapy to limit antibiotic duration in critically ill patients
De-escalate to narrow-spectrum agents once culture/sensitivity data available
Avoid antibiotics for confirmed viral pneumonia

Key Sources:

Goldman-Cecil Medicine, pp. 1001–1002 (HAP/VAP treatment)
Tintinalli's Emergency Medicine, pp. 856–857 (pediatric pneumonia, empiric regimens)

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