What is the recommended antibiotic regimen for a patient with Hospital-Acquired Pneumonia (HAP)?

Antibiotic Treatment for Hospital-Acquired Pneumonia

For patients with hospital-acquired pneumonia (HAP), initiate empiric therapy with piperacillin-tazobactam 4.5g IV every 6 hours as the backbone regimen, adding vancomycin or linezolid for MRSA coverage if risk factors are present, and a second antipseudomonal agent (fluoroquinolone or aminoglycoside) for high-risk patients. 1

Risk Stratification Framework

The treatment approach depends on two critical assessments: mortality risk and MRSA risk factors. 1, 2

High Mortality Risk Factors

• Need for ventilatory support due to pneumonia 1, 2
• Septic shock at presentation 1, 2

MRSA Risk Factors

• Prior IV antibiotic use within 90 days (most important risk factor) 1, 3
• Hospitalization in a unit where >20% of S. aureus isolates are methicillin-resistant 1, 3
• Unknown MRSA prevalence in your unit 1, 3
• Prior MRSA detection by culture or screening 3

Treatment Algorithm by Risk Category

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

Monotherapy with one of the following: 1, 2

• Piperacillin-tazobactam 4.5g IV q6h (preferred) 1, 4
• Cefepime 2g IV q8h 1, 2
• Levofloxacin 750mg IV daily 1, 2
• Imipenem 500mg IV q6h 1
• Meropenem 1g IV q8h 1

Moderate-Risk Patients (No High Mortality Risk, BUT MRSA Risk Factors Present)

Base regimen PLUS MRSA coverage: 1, 2

Choose one base agent: 1

• Piperacillin-tazobactam 4.5g IV q6h
• Cefepime or ceftazidime 2g IV q8h
• Levofloxacin 750mg IV daily
• Ciprofloxacin 400mg IV q8h
• Imipenem 500mg IV q6h
• Meropenem 1g IV q8h

PLUS one MRSA agent: 1

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

High-Risk Patients (High Mortality Risk OR Recent IV Antibiotics Within 90 Days)

Dual antipseudomonal coverage PLUS MRSA coverage if risk factors present: 1, 2

Choose TWO agents from different classes (avoid two β-lactams): 1

• 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 1
• Meropenem 1g IV q8h 1
• Amikacin 15-20mg/kg IV daily 1
• Gentamicin 5-7mg/kg IV daily 1
• Tobramycin 5-7mg/kg IV daily 1
• Aztreonam 2g IV q8h (if severe penicillin allergy) 1

PLUS MRSA coverage if risk factors present: 1

• Vancomycin 15mg/kg IV q8-12h (target trough 15-20 mg/mL) 1
• Linezolid 600mg IV q12h 1

Critical Implementation Points

Administration Details

• All IV antibiotics must be infused over 30 minutes 4, 5
• Piperacillin-tazobactam and aminoglycosides should be reconstituted, diluted, and administered separately (co-administration via Y-site possible under certain conditions) 5

Local Antibiogram Integration

• Base empiric regimens on local distribution of pathogens and their antimicrobial susceptibilities 1
• Hospitals should regularly generate and disseminate local antibiograms tailored to HAP populations 1
• Modify the 10-20% MRSA prevalence threshold based on your institution's data 1

De-escalation Strategy

• Obtain respiratory cultures before initiating antibiotics 3
• Narrow therapy once susceptibilities return to avoid unnecessary broad-spectrum coverage 3
• For confirmed MSSA, narrow to oxacillin, nafcillin, or cefazolin (preferred over broader agents) 2

Common Pitfalls to Avoid

Severe Penicillin Allergy

• If using aztreonam, you MUST add MSSA coverage (vancomycin or linezolid) due to aztreonam's lack of gram-positive activity 1, 4, 2

Inappropriate Monotherapy

• Never use monotherapy in high-risk patients who require combination therapy 2
• Monotherapy for pseudomonal HAP is associated with rapid resistance evolution and high clinical failure rates 6

Renal Dosing

• Adjust all dosages for creatinine clearance ≤40 mL/min and dialysis patients to avoid toxicity 5
• Patients with renal impairment receiving higher doses are at greater risk for neuromuscular excitability or seizures 5

Monitoring Requirements

• Monitor hematologic tests during prolonged therapy (risk of bleeding, leukopenia, neutropenia) 5
• Closely monitor patients with renal impairment or seizure disorders for signs of neuromuscular excitability 5
• Be aware that piperacillin-tazobactam is an independent risk factor for renal failure in critically ill patients 5