What is the typical antibiotic (abx) regimen for Hospital-Acquired Pneumonia (HAP) treatment?

Hospital-Acquired Pneumonia (HAP) Antibiotic Treatment

For HAP without high mortality risk or MRSA risk factors, use monotherapy with piperacillin-tazobactam 4.5g IV every 6 hours, cefepime 2g IV every 8 hours, levofloxacin 750mg IV daily, imipenem 500mg IV every 6 hours, or meropenem 1g IV every 8 hours. 1

Risk Stratification Determines Antibiotic Selection

The 2016 IDSA/ATS guidelines provide a clear algorithmic approach based on mortality risk and MRSA risk factors 1:

Low Mortality Risk WITHOUT MRSA Risk Factors

• Single agent therapy is sufficient 1
• Options include:
  • Piperacillin-tazobactam 4.5g IV q6h 1
  • Cefepime 2g IV q8h 1
  • Levofloxacin 750mg IV daily 1
  • Imipenem 500mg IV q6h 1
  • Meropenem 1g IV q8h 1

Low Mortality Risk WITH MRSA Risk Factors

• Add MRSA coverage to gram-negative coverage 1
• Gram-negative options (choose one):
  • Piperacillin-tazobactam 4.5g IV q6h 1
  • Cefepime or ceftazidime 2g IV q8h 1
  • Levofloxacin 750mg IV daily 1
  • Ciprofloxacin 400mg IV q8h 1
  • Imipenem 500mg IV q6h or meropenem 1g IV q8h 1
  • Aztreonam 2g IV q8h (if severe penicillin allergy) 1
• Plus MRSA coverage:
  • Vancomycin 15mg/kg IV q8-12h (target trough 15-20 mg/mL) 1
  • OR Linezolid 600mg IV q12h 1

High Mortality Risk OR Recent IV Antibiotics

• Use dual gram-negative coverage plus MRSA coverage 1
• Select two agents from different classes (avoid two β-lactams):
  • β-lactam: Piperacillin-tazobactam 4.5g IV q6h, cefepime/ceftazidime 2g IV q8h, imipenem 500mg IV q6h, or meropenem 1g IV q8h 1
  • Plus fluoroquinolone: Levofloxacin 750mg IV daily or ciprofloxacin 400mg IV q8h 1
  • OR aminoglycoside: Amikacin 15-20mg/kg IV daily, gentamicin 5-7mg/kg IV daily, or tobramycin 5-7mg/kg IV daily 1
• Plus MRSA coverage: Vancomycin or linezolid (doses as above) 1

Critical Risk Factor Definitions

High Mortality Risk Includes:

• Need for ventilatory support due to pneumonia 1
• Septic shock 1

MRSA Risk Factors Include:

• Prior IV antibiotic use within 90 days 1
• Treatment in a unit where >20% of S. aureus isolates are methicillin-resistant 1
• Unknown MRSA prevalence 1
• Prior MRSA detection by culture or screening 1

Dual Pseudomonal Coverage Indicated When:

• Prior IV antibiotic use within 90 days 1
• Structural lung disease (bronchiectasis, cystic fibrosis) 1
• High-quality gram stain showing predominant gram-negative bacilli 1

Common Pitfalls and How to Avoid Them

Never use aminoglycosides as sole antipseudomonal coverage 1. Aminoglycosides should only be used in combination with a β-lactam or fluoroquinolone 1.

Avoid two β-lactams together 1. The exception is aztreonam, which can be combined with another β-lactam due to different cell wall targets 1.

If using aztreonam for severe penicillin allergy, add MSSA coverage 1. Aztreonam lacks gram-positive activity, so add vancomycin or linezolid even without MRSA risk factors 1.

Local antibiogram data should modify these recommendations 1. If your institution has >20% MRSA prevalence, empiric MRSA coverage becomes mandatory 1. Research demonstrates significant institutional variation in resistance patterns, with some facilities showing <10% ciprofloxacin susceptibility among resistant gram-negatives but >80% amikacin susceptibility 2.

Duration and De-escalation

Treatment duration is typically 7-10 days for standard HAP 3. The 2005 ATS guidelines recommend 7-8 days for uncomplicated cases with good clinical response 1.

Obtain respiratory cultures before starting antibiotics 1. Negative cultures obtained without recent antibiotic changes can guide de-escalation 1.

De-escalate based on culture results and clinical response 1. Once susceptibilities return, narrow to the most appropriate targeted therapy 1.