What is the recommended antibiotic coverage for hospital-acquired pneumonia (HAP)?

Hospital-Acquired Pneumonia Antibiotic Coverage

Empiric Coverage Strategy

For hospital-acquired pneumonia, empiric antibiotic therapy must cover Staphylococcus aureus (including MRSA in high-risk patients) and gram-negative pathogens including Pseudomonas aeruginosa, with treatment stratified by mortality risk and MRSA risk factors. 1

Risk Stratification Framework

Low-Risk Patients (No MRSA Risk Factors, Not High Mortality Risk)

Monotherapy targeting MSSA and gram-negative pathogens:

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

These regimens provide adequate coverage for methicillin-sensitive S. aureus, Haemophilus influenzae, Klebsiella pneumoniae, and other common gram-negative pathogens without MRSA coverage. 1

Moderate-Risk Patients (MRSA Risk Factors Present, Not High Mortality Risk)

Add MRSA coverage to the above gram-negative regimen:

• Use one of the above antipseudomonal agents (piperacillin-tazobactam, cefepime, levofloxacin, or carbapenem) 1, 2
• PLUS Vancomycin 15 mg/kg IV q8-12h (target trough 15-20 mg/mL) OR Linezolid 600 mg IV q12h 1, 2

MRSA risk factors include: 1, 2

• Prior IV antibiotic use within 90 days
• Hospitalization in a unit where >20% of S. aureus isolates are methicillin-resistant or prevalence unknown
• Prior MRSA colonization or infection

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

Dual antipseudomonal coverage plus MRSA coverage:

Two agents from different classes (avoid combining two β-lactams): 1, 2

• Piperacillin-tazobactam 4.5 g IV q6h 1, 3
• OR Cefepime or ceftazidime 2 g IV q8h 1
• OR Imipenem 500 mg IV q6h or Meropenem 1 g IV q8h 1
• OR Aztreonam 2 g IV q8h (if severe penicillin allergy) 1

Combined with one of: 1, 2

• Levofloxacin 750 mg IV daily or Ciprofloxacin 400 mg IV q8h
• OR Amikacin 15-20 mg/kg IV daily, Gentamicin 5-7 mg/kg IV daily, or Tobramycin 5-7 mg/kg IV daily

PLUS MRSA coverage: 1, 2

• Vancomycin 15 mg/kg IV q8-12h (consider loading dose 25-30 mg/kg for severe illness) OR Linezolid 600 mg IV q12h

High mortality risk factors include: 1, 2

• Need for ventilatory support due to pneumonia
• Septic shock

Special Considerations for Nosocomial Pneumonia

For FDA-labeled nosocomial pneumonia treatment, piperacillin-tazobactam is specifically indicated at 4.5 g IV q6h plus an aminoglycoside for moderate to severe cases, with treatment duration of 7-14 days. 3 The aminoglycoside should be continued if P. aeruginosa is isolated. 3

De-escalation Strategy

Once culture results return, narrow therapy based on susceptibilities: 1

• For confirmed MSSA, switch to oxacillin, nafcillin, or cefazolin (preferred over broader agents like piperacillin-tazobactam or cefepime for targeted therapy) 1, 2
• Discontinue MRSA coverage if cultures are negative for MRSA 1
• Adjust gram-negative coverage based on identified pathogens and susceptibilities 1

Critical Pitfalls to Avoid

Do not use monotherapy in high-risk patients who require combination therapy for adequate pseudomonal coverage—this increases treatment failure rates. 2

Do not use unnecessary broad-spectrum antibiotics in low-risk patients without MRSA risk factors, as this drives antimicrobial resistance without improving outcomes. 2

For severe penicillin allergy requiring aztreonam, ensure MSSA coverage is maintained with an additional agent, as aztreonam lacks gram-positive activity. 1, 2

Local antibiogram data should guide empiric choices when institutional resistance patterns differ significantly from these general recommendations. 1