Empiric Antibiotic Therapy for Hospital-Acquired Pneumonia (HAP)

Introduction to HAP Treatment

The Infectious Diseases Society of America recommends that empiric antibiotic therapy for hospital-acquired pneumonia should be based on risk factors for mortality and MRSA, with patients at low risk of mortality and without MRSA risk factors receiving monotherapy with piperacillin-tazobactam, cefepime, levofloxacin, imipenem, or meropenem, while patients at high risk of mortality or with MRSA risk factors should receive combination therapy with two antipseudomonal agents plus MRSA coverage 1, 2, 3

For patients with low risk of mortality and no MRSA risk factors, the American Thoracic Society suggests using one of the following as monotherapy: piperacillin-tazobactam 4.5 g IV q6h 1, 3, 4, or levofloxacin 750 mg IV daily 5
For patients with low risk of mortality but with MRSA risk factors, the Infectious Diseases Society of America recommends using one of the following antipseudomonal agents: piperacillin-tazobactam 4.5 g IV q6h 1, 2, 4, or levofloxacin 750 mg IV daily 5, plus MRSA coverage with vancomycin or linezolid 1, 6, 5
For patients with high risk of mortality or recent IV antibiotics, the American Thoracic Society suggests using two antipseudomonal agents from different classes, such as piperacillin-tazobactam, cefepime, ceftazidime, meropenem, imipenem, aztreonam, ciprofloxacin, levofloxacin, or an aminoglycoside 1, 3, 4, plus MRSA coverage with vancomycin or linezolid 1, 6, 5

The Infectious Diseases Society of America identifies prior intravenous antibiotic use within 90 days 3, hospitalization in a unit where >20% of S. aureus isolates are methicillin-resistant 3, unknown MRSA prevalence in the unit 3, and prior detection of MRSA by culture 3 as MRSA risk factors
The American Thoracic Society considers need for ventilatory support due to HAP 3 and septic shock 3 as mortality risk factors
The Infectious Diseases Society of America notes that structural lung disease (bronchiectasis, cystic fibrosis) 6 and gram stain showing numerous gram-negative bacilli 6 are risk factors for gram-negative infections

The Infectious Diseases Society of America recommends that dosing should be optimized using pharmacokinetic/pharmacodynamic principles rather than simply following manufacturer's prescribing information 6
The American Thoracic Society suggests that extended infusions may be appropriate for beta-lactams to optimize drug exposure 3
For patients with HAP due to P. aeruginosa, the Infectious Diseases Society of America recommends that definitive therapy should be based on antimicrobial susceptibility testing results 6

The Infectious Diseases Society of America emphasizes that empiric therapy should be based on local antibiogram data whenever possible 1, 2
The American Thoracic Society notes that aminoglycosides should never be used as monotherapy for HAP, even when the isolate appears susceptible 6, 3
For patients with HAP due to P. aeruginosa who remain in septic shock when susceptibility results are known, the Infectious Diseases Society of America suggests combination therapy with two active agents 6