What is the initial treatment for bacterial pneumonia?

Initial Treatment for Bacterial Pneumonia

For community-acquired pneumonia (CAP), treatment should be initiated immediately upon diagnosis with empiric antibiotics selected based on severity of illness and treatment setting: outpatients without comorbidities should receive amoxicillin or a macrolide; hospitalized non-ICU patients require a β-lactam (ceftriaxone or cefotaxime) plus a macrolide or a respiratory fluoroquinolone alone; and ICU patients need combination therapy with a non-antipseudomonal cephalosporin III plus macrolide or a respiratory fluoroquinolone. 1

Timing of Antibiotic Administration

• Antibiotics must be started immediately after diagnosis of pneumonia 2, 1
• In patients with septic shock, any delay in antibiotic administration increases mortality 2

Outpatient Treatment Algorithm

Previously Healthy Adults (No Risk Factors)

• First-line: Amoxicillin 1
• Alternative: Macrolide (azithromycin preferred) 1
• These patients can be treated entirely with oral antibiotics from the start 2

Outpatients with Comorbidities or Recent Antibiotic Use

• Respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin) 1, 3
• Alternative: β-lactam plus macrolide combination 1
• Recent antibiotic use within 90 days is a critical risk factor requiring broader coverage 2

Hospitalized Non-ICU Patients

Standard regimen options include: 1

• β-lactam (ceftriaxone 1-2g daily or cefotaxime 2g q8h) PLUS macrolide (azithromycin) 2, 1
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin) 2, 1
• Other options: Aminopenicillin/β-lactamase inhibitor plus macrolide 2

The combination of β-lactam plus macrolide provides coverage for both typical bacteria (S. pneumoniae, H. influenzae) and atypical pathogens (Mycoplasma, Chlamydophila, Legionella) 1, 4

Severe CAP/ICU Patients

Without Pseudomonas Risk Factors

• Non-antipseudomonal cephalosporin III (ceftriaxone or cefotaxime) PLUS macrolide 2, 1
• Alternative: Moxifloxacin or levofloxacin ± non-antipseudomonal cephalosporin III 2, 1

With Pseudomonas Risk Factors

Risk factors include: structural lung disease, recent hospitalization, recent broad-spectrum antibiotics, or immunosuppression 2

Combination therapy required: 2, 1

• Antipseudomonal β-lactam (cefepime, ceftazidime, piperacillin-tazobactam, or meropenem) PLUS ciprofloxacin 2
• Alternative: Antipseudomonal β-lactam PLUS macrolide PLUS aminoglycoside (gentamicin, tobramycin, or amikacin) 2
• Meropenem is preferred among carbapenems, with doses up to 6g daily possible in severe cases 2

Critical caveat: If ceftazidime is used, it must be combined with penicillin G for adequate S. pneumoniae coverage 2

Hospital-Acquired Pneumonia (HAP)

Low Mortality Risk, No MRSA Risk Factors

Monotherapy options: 2

• Piperacillin-tazobactam 4.5g IV q6h
• Cefepime 2g IV q8h
• Levofloxacin 750 mg IV daily
• Imipenem 500 mg IV q6h or meropenem 1g IV q8h

MRSA Risk Factors Present

MRSA risk factors include: prior IV antibiotics within 90 days, hospitalization in unit where >20% of S. aureus is methicillin-resistant, or high mortality risk 2

Add MRSA coverage: 2

• Vancomycin 15 mg/kg IV q8-12h (target trough 15-20 mg/mL) 2
• Alternative: Linezolid 600 mg IV q12h 2
• Consider loading dose of vancomycin 25-30 mg/kg for severe illness 2

High Mortality Risk or Recent Antibiotics

Use two agents from different classes (avoid two β-lactams): 2

• Antipseudomonal β-lactam PLUS fluoroquinolone OR aminoglycoside
• PLUS vancomycin or linezolid for MRSA coverage 2

Duration of Therapy

• Standard duration: 5-8 days for responding patients 2, 1
• Minimum 5 days with patient afebrile for 48-72 hours and ≤1 sign of clinical instability 1
• Maximum should not exceed 8 days in responding patients 2, 1
• Procalcitonin (PCT) biomarkers may guide shorter treatment duration 2

IV to Oral Switch Strategy

• Outpatient pneumonia can be treated orally from the beginning 2
• Hospitalized patients should switch to oral when clinically stable 2
• Clinical stability criteria include: improving respiratory parameters, hemodynamic stability, and ability to take oral medications 2
• Most patients do not need to remain hospitalized after switching to oral therapy 2
• Sequential therapy using the same drug (e.g., IV to oral levofloxacin) is preferred 2, 3

Special Pathogen Considerations

Multi-Drug Resistant S. pneumoniae (MDRSP)

• Use 7-14 day regimen (not 5-day) with respiratory fluoroquinolone or β-lactam plus macrolide 3
• Levofloxacin achieves 95% clinical success against MDRSP 3, 4

Legionella Species

• Levofloxacin or moxifloxacin preferred 2, 1
• Alternative: Azithromycin ± rifampicin 2, 1

Aspiration Pneumonia

Hospital ward (from home): 2

• β-lactam/β-lactamase inhibitor OR
• Clindamycin OR
• Moxifloxacin

ICU or nursing home origin: 2

• Clindamycin plus cephalosporin

Common Pitfalls to Avoid

• Never delay antibiotics waiting for culture results—empiric therapy must start immediately 2, 1
• Do not use 5-day levofloxacin regimen for MDRSP—requires 7-14 days 3
• Avoid fluoroquinolone monotherapy if recent fluoroquinolone use within 90 days 2
• Remember ceftazidime lacks adequate pneumococcal coverage—must add penicillin G 2
• Do not continue antibiotics beyond 8 days in responding patients—increases resistance risk 2, 1
• Steroids are not recommended for pneumonia treatment 2