What is the recommended management for a patient with acquired hospital pneumonia, considering their medical history and potential for resistant organisms?

Management of Hospital-Acquired Pneumonia

All patients with hospital-acquired pneumonia (HAP) require empiric antibiotic coverage against S. aureus, with the decision to cover MRSA versus MSSA based on specific risk factors, and the choice of additional gram-negative coverage determined by mortality risk and recent antibiotic exposure. 1

Risk Stratification Framework

The management algorithm hinges on three critical decision points that determine antibiotic selection 1:

1. Assess Mortality Risk

High-risk features include 1:

• Need for ventilatory support due to pneumonia
• Septic shock at presentation

2. Identify MRSA Risk Factors

Add MRSA coverage if ANY of the following are present 1:

• IV antibiotic use within prior 90 days
• Hospitalization in a unit where >20% of S. aureus isolates are methicillin-resistant
• MRSA prevalence unknown in your unit
• High risk of mortality (as defined above)

3. Determine Need for Dual Gram-Negative Coverage

Required when 1:

• High risk of mortality present
• Receipt of IV antibiotics within prior 90 days

Empiric Antibiotic Regimens

Low-Risk Patients (No Mortality Risk, No MRSA Risk Factors)

Use monotherapy with ONE of the following 1:

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

These regimens provide adequate MSSA coverage without requiring specific anti-MRSA agents 1.

Moderate-Risk Patients (MRSA Risk Factors Present, But Low Mortality Risk)

Use the same gram-negative coverage as above PLUS add MRSA coverage 1:

• Vancomycin 15 mg/kg IV q8-12h (target trough 15-20 mg/mL; consider loading dose 25-30 mg/kg × 1 for severe illness)
• OR Linezolid 600 mg IV q12h

High-Risk Patients (High Mortality Risk OR Recent IV Antibiotics)

Use dual gram-negative coverage (TWO agents from different classes, avoiding two β-lactams) PLUS MRSA coverage 1:

Select TWO from different categories 1:

• β-lactams: Piperacillin-tazobactam 4.5 g IV q6h, cefepime 2 g IV q8h, ceftazidime 2 g IV q8h, imipenem 500 mg IV q6h, or meropenem 1 g IV q8h
• Fluoroquinolones: Levofloxacin 750 mg IV daily or ciprofloxacin 400 mg IV q8h
• Aminoglycosides: Amikacin 15-20 mg/kg IV daily, gentamicin 5-7 mg/kg IV daily, or tobramycin 5-7 mg/kg IV daily
• Monobactam: Aztreonam 2 g IV q8h

PLUS add MRSA coverage 1:

• Vancomycin 15 mg/kg IV q8-12h (target trough 15-20 mg/mL)
• OR Linezolid 600 mg IV q12h

Special Considerations for Nosocomial Pneumonia

For nosocomial pneumonia specifically, piperacillin-tazobactam 4.5 g IV q6h plus an aminoglycoside is FDA-approved and recommended, particularly when P. aeruginosa is suspected. 2 The FDA label explicitly states that nosocomial pneumonia caused by P. aeruginosa should be treated in combination with an aminoglycoside 2.

The recommended duration for nosocomial pneumonia is 7-14 days 2, which is longer than the 7-10 days recommended for other HAP indications 2.

Treatment Duration and De-escalation

• Standard duration: 7-10 days for most HAP cases 2
• Nosocomial pneumonia: 7-14 days 2
• De-escalate therapy at 48-72 hours based on culture results and clinical response 1
• Discontinue MRSA coverage if cultures are negative for MRSA and patient is clinically improving 1

Renal Dose Adjustments

For patients with creatinine clearance ≤40 mL/min, reduce piperacillin-tazobactam dosing 2:

• CrCl 20-40 mL/min: 3.375 g q6h (for HAP) or 2.25 g q6h (for nosocomial pneumonia)
• CrCl <20 mL/min: 2.25 g q8h (for HAP) or 2.25 g q6h (for nosocomial pneumonia)
• Hemodialysis: 2.25 g q12h (for HAP) or 2.25 g q8h (for nosocomial pneumonia), plus 0.75 g after each dialysis session

Critical Pitfalls to Avoid

Do not use ciprofloxacin monotherapy for HAP - it has poor activity against S. pneumoniae and lacks anaerobic coverage, leading to high treatment failure rates 3. If a fluoroquinolone is needed, use levofloxacin 750 mg daily or moxifloxacin 400 mg daily 1, 3.

Do not routinely add anaerobic coverage unless lung abscess or empyema is suspected 3. Modern data shows gram-negative pathogens and S. aureus predominate, not anaerobes 3.

Do not delay antibiotics waiting for cultures - this is consistently associated with increased mortality 3. Start empiric therapy immediately and adjust based on culture results at 48-72 hours 3.

Do not assume all HAP requires MRSA coverage - only 65% of clinically diagnosed HAP cases meet radiological criteria, and overuse of broad-spectrum antibiotics drives resistance 4. Use the risk stratification algorithm above to guide MRSA coverage decisions 1.

Avoid using two β-lactams together in combination regimens - select agents from different antibiotic classes 1.

Monitoring and Reassessment

• Clinical stability criteria: Temperature ≤37.8°C, heart rate ≤100 bpm, respiratory rate ≤24 breaths/min, systolic BP ≥90 mmHg 3
• Measure C-reactive protein on days 1 and 3-4 to assess response 3
• If no improvement by 72 hours, consider complications (empyema, abscess), resistant organisms, alternative diagnoses, or infection at another site 3