Hospital-Acquired Pneumonia
System: Respiratory Infections · Parent MOC: MOC - Diseases by System
Includes: Ventilator-associated pneumonia (VAP) as the ventilated subset · see also Device-Associated Infections
One-Sentence Definition
Pneumonia acquired ≥48 hours after hospital admission (VAP: after endotracheal intubation), typically involving healthcare-associated Gram-negatives and S. aureus, with high AMR risk.
Clinical Presentation
- New/worsening infiltrate + fever, leukocytosis, purulent secretions, worsening oxygenation
- VAP: same after ≥48h mechanical ventilation
Pathogens
| Context | Organism | Notes |
|---|---|---|
| Common GNR | Pseudomonas aeruginosa · Klebsiella pneumoniae · Escherichia coli | MDR risk |
| Gram-positive | Staphylococcus aureus (MSSA/MRSA) | Local MRSA rates matter |
| Other | Acinetobacter, Stenotrophomonas (TBD) | Often MDR |
Pathogenesis
- Microaspiration of colonizing ICU flora; biofilm on ETT (Biofilm)
- Prior antibiotics select resistant populations (Mutation and Selection · HGT)
Diagnosis
| Step | Test | Note |
|---|---|---|
| Clinical + imaging | CXR/CT | Nonspecific in ICU |
| Lower tract sample | ETA / BAL culture (quant when available) | Interpret colonization carefully |
| Blood cultures | Concurrent bacteremia | Source staging |
| MRSA/PCR nasal | Rule-out adjunct | Negative predictive value used in stewardship |
Treatment Principles
- Empiric: cover Pseudomonas + MSSA/MRSA per risk and local antibiogram
- Narrow at 48–72h with cultures; prefer shorter courses when improving
- Source: ventilation bundle, minimize devices
Prevention
- HOB elevation, oral care, sedation vacation, DVT/PUD prophylaxis bundles
- Stewardship to limit unnecessary broad agents
Differential / Pitfalls
- ARDS, atelectasis, aspiration without infection, CHF
- Treating colonizers in ETA culture without clinical pneumonia
Learning Aids
Clinical Example
Example
Case: Day 6 ICU, vented; new infiltrate, purulent ETA; Gram-neg rods on smear.
Question: Empiric thinking and which organism is classic?
Answer: HAP/VAP — cover Pseudomonas aeruginosa ± MRSA per risk; obtain cultures; narrow with AST; review device care (Device-Associated Infections).
Related
- Community-Acquired Pneumonia · Device-Associated Infections
- Pseudomonas aeruginosa · Staphylococcus aureus · MOC - Antimicrobial Resistance (AMR)
Active Recall
- Time threshold that defines HAP vs CAP?
- Why is antibiogram essential in HAP empiric choice?
- Role of biofilm on the endotracheal tube?