Management of Hospital-Acquired Pneumonia (HAP)

Risk Stratification and Empiric Antibiotic Selection

The European Respiratory Society recommends stratifying patients by risk factors for multidrug-resistant (MDR) pathogens and septic shock, then initiating empiric antibiotics accordingly: narrow-spectrum monotherapy for low-risk patients, or broad-spectrum combination therapy covering Pseudomonas aeruginosa, ESBL-producing organisms, and MRSA for high-risk patients 1, 2, 3
Low-risk patients include those without septic shock, no prior antibiotic use within 90 days, hospitalization ≤5 days, no previous MDR colonization, and local ICU resistance rates <25% 1, 2, 4
High-risk patients present with septic shock and/or: prior antibiotic use within 90 days, prolonged hospitalization (>5 days), previous MDR colonization, or local ICU resistance rates >25% for MDR pathogens 1, 4, 5

For low-risk HAP, use narrow-spectrum monotherapy with ertapenem, ceftriaxone, cefotaxime, moxifloxacin, or levofloxacin 750 mg IV/PO daily 1, 2, 6, 7
Third-generation cephalosporins carry higher risk of Clostridioides difficile infection compared to penicillins or quinolones 1, 2
For high-risk HAP, initiate combination therapy with an antipseudomonal beta-lactam (piperacillin-tazobactam 4.5g IV q6h, cefepime 2g IV q8h, meropenem 1g IV q8h, or imipenem 500mg IV q6h) PLUS coverage for MRSA if risk factors present 1, 4, 5, 3, 6
For MRSA coverage, use vancomycin 15 mg/kg IV q8-12h or linezolid 600 mg IV/PO q12h 3, 6, 7

Obtain lower respiratory tract samples (distal quantitative, proximal quantitative, or qualitative culture) before initiating antibiotics to guide de-escalation 1
Distal quantitative samples in stable patients reduce antibiotic exposure and improve diagnostic accuracy 1
Reassess at 48-72 hours using temperature trends, white blood cell count, chest radiography, oxygenation parameters, and hemodynamic stability 8
Tailor therapy to culture susceptibilities by day 3—this represents good practice 1, 2, 4
De-escalate from combination to monotherapy once cultures identify susceptible organisms, unless treating XDR/PDR nonfermenting gram-negatives or carbapenem-resistant Enterobacteriaceae 1, 2, 4, 5

Treat for 7-8 days in patients with good clinical response, no immunodeficiency, and no complications (lung abscess, empyema, cavitation, necrotizing pneumonia) 4, 5, 3, 8
Longer courses may be necessary for immunocompromised patients, those with complications, or inadequate initial empiric therapy 8

Local antibiograms should guide empiric therapy—the ICU-specific resistance rate (not hospital-wide) is the relevant factor 1, 2, 4
Negative culture results are most reliable when obtained before antibiotics or within 72 hours of antibiotic changes 8