Treatment for Hospital-Acquired Pneumonia
For hospital-acquired pneumonia, treatment should be stratified by mortality risk and MRSA risk factors: low-risk patients without MRSA risk factors receive monotherapy with piperacillin-tazobactam, cefepime, levofloxacin, imipenem, or meropenem; patients with MRSA risk factors add vancomycin or linezolid; and high-risk patients receive dual antipseudomonal therapy plus MRSA coverage. 1
Risk Stratification Framework
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 1
- Cefepime 2 g IV q8h 1
- Levofloxacin 750 mg IV daily 1
- Imipenem 500 mg IV q6h 1
- Meropenem 1 g IV q8h 1
Patients with MRSA Risk Factors (But Low Mortality Risk)
Use the same monotherapy options PLUS MRSA coverage: 1
- Vancomycin 15 mg/kg IV q8-12h (target trough 15-20 mg/mL; consider loading dose 25-30 mg/kg for severe illness) 1
- OR Linezolid 600 mg IV q12h 1
MRSA risk factors include: 1
- Prior IV antibiotic use within 90 days 1
- Hospitalization in a unit where >20% of S. aureus isolates are methicillin-resistant 1
- Unknown MRSA prevalence in the unit 1
High-Risk Patients (High Mortality Risk OR Recent IV Antibiotics)
Use TWO antipseudomonal agents from different classes (avoid combining two β-lactams) PLUS MRSA coverage: 1
Select TWO from different classes: 1
- Piperacillin-tazobactam 4.5 g IV q6h 1
- Cefepime or ceftazidime 2 g IV q8h 1
- Levofloxacin 750 mg IV daily OR ciprofloxacin 400 mg IV q8h 1
- Imipenem 500 mg IV q6h OR meropenem 1 g IV q8h 1
- Aminoglycoside: amikacin 15-20 mg/kg IV daily, gentamicin 5-7 mg/kg IV daily, or tobramycin 5-7 mg/kg IV daily 1
- Aztreonam 2 g IV q8h 1
PLUS MRSA coverage with vancomycin or linezolid (doses as above) 1
High mortality risk factors include: 1
Special Considerations
Structural Lung Disease
Patients with bronchiectasis or cystic fibrosis require two antipseudomonal agents regardless of other risk factors due to increased risk of gram-negative infections. 1
Local Antibiogram Data
All empiric regimens must be based on local antibiogram data whenever possible, as resistance patterns vary significantly between institutions. 1 The threshold of >20% MRSA prevalence for empiric MRSA coverage can be adjusted based on local epidemiology. 1
Duration of Therapy
Treat for 7 days in most cases, with adjustments based on clinical response, radiologic improvement, and laboratory parameters. 2 For nosocomial pneumonia specifically, the FDA-approved duration for piperacillin-tazobactam is 7-14 days. 3
De-escalation Strategy
Once culture results are available (typically day 3), narrow therapy to target identified pathogens based on susceptibility testing. 1 This "de-escalation" approach improves outcomes without increasing resistance. 4
Critical Pitfalls to Avoid
Never use aminoglycosides as monotherapy for HAP, even when the isolate appears susceptible, as this is associated with treatment failure. 5, 2
Avoid using two β-lactams together in combination regimens, as they have overlapping mechanisms and do not provide synergy. 1
Do not add routine anaerobic coverage unless there is documented aspiration with necrotizing pneumonia or lung abscess, as standard HAP regimens (particularly piperacillin-tazobactam) already provide adequate anaerobic coverage. 6
Prompt administration is critical - delays in appropriate antibiotic therapy are associated with increased mortality. 6, 5
Pharmacokinetic Optimization
Consider extended infusions for β-lactams (infusing over 3-4 hours rather than 30 minutes) to optimize time-dependent killing and drug exposure. 6, 5
Dose based on pharmacokinetic/pharmacodynamic principles rather than simply following standard prescribing information, particularly in critically ill patients. 5