What are the diagnostic criteria and treatment guidelines for hospital-acquired pneumonia (HAP)?

Hospital-Acquired Pneumonia Diagnostic Criteria and Treatment Guidelines

Hospital-acquired pneumonia (HAP) should be diagnosed using clinical criteria including new or progressive radiographic infiltrates plus at least two of the following: fever, leukocytosis or leukopenia, and purulent secretions. 1

Diagnostic Criteria

Definition

• HAP is defined as pneumonia that occurs 48 hours or more after hospital admission and was not incubating at the time of admission 2
• Ventilator-associated pneumonia (VAP) refers to pneumonia that arises more than 48-72 hours after endotracheal intubation 2

Clinical and Radiological Criteria

HAP diagnosis requires:

• New or progressive radiographic infiltrates on chest imaging 2
• Plus at least one of the following:
  • Body temperature > 38.3°C without any other cause
  • Leukocytes < 4,000/mm³ or > 12,000/mm³
• And at least two of the following:
  • Purulent sputum
  • Cough or dyspnea
  • Declining oxygenation or increased oxygen requirements 2

Important Diagnostic Considerations

• Chest radiography is essential for confirming HAP diagnosis, as clinical symptoms alone are not specific 3
• Studies show that up to 35% of patients treated for HAP may not meet objective radiological criteria 4
• Microbiological confirmation should be attempted before starting antibiotics 1
• Respiratory samples should be obtained from all patients with suspected HAP 2

Microbiological Diagnosis

Sampling Methods

• Lower respiratory tract samples should be collected before antibiotic changes 2
• Sampling options include:
  • Endotracheal aspirates
  • Bronchoalveolar lavage (BAL)
  • Protected specimen brush (PSB) 2
• Blood cultures should be collected in all patients with suspected VAP 2

Common Pathogens

• Early-onset HAP (<5 days of hospitalization):
  • Methicillin-susceptible Staphylococcus aureus
  • Streptococcus pneumoniae
  • Haemophilus influenzae 2
• Late-onset HAP (≥5 days):
  • Enterobacteriaceae
  • Pseudomonas aeruginosa
  • Acinetobacter baumannii
  • Methicillin-resistant S. aureus 2, 5
• Polymicrobial infection occurs in approximately 30% of cases 2, 5

Risk Stratification

Risk Factors for Multidrug-Resistant (MDR) Pathogens

• Late-onset pneumonia (≥5 days of hospitalization)
• Prior antibiotic use within 90 days
• High local prevalence of antibiotic resistance (>25%)
• Healthcare-associated risk factors:
  • Hospitalization for ≥2 days within past 90 days
  • Residence in nursing home or long-term care facility
  • Recent IV antibiotics, chemotherapy, or wound care within past 30 days
  • Hemodialysis clinic attendance 2, 1
• Previous surgery and/or endotracheal intubation 4

Treatment Guidelines

Empiric Antibiotic Therapy

For Patients at Low Risk for MDR Pathogens

• Narrow-spectrum antibiotics:
  • Ceftriaxone or
  • Ampicillin-sulbactam or
  • Ertapenem 1

For Patients at High Risk for MDR Pathogens

• Antipseudomonal β-lactam (choose one):
  • Piperacillin-tazobactam 4.5g IV every 6 hours 6
  • Cefepime
  • Meropenem
  • Imipenem
• Plus MRSA coverage if risk factors present (choose one):
  • Vancomycin
  • Linezolid 1
• For suspected Pseudomonas infection, combination therapy with an aminoglycoside is recommended 6, 5

Treatment Duration

• Standard duration: 7-8 days for patients with good clinical response 1
• Extended duration (10-14 days) may be necessary for:
  • Infections with non-fermenting gram-negative bacilli
  • Inadequate initial clinical response 2

Management Approach

1. Obtain appropriate cultures before starting antibiotics
2. Start empiric therapy based on risk factors for MDR pathogens
3. Reassess at 48-72 hours based on clinical response and culture results
4. De-escalate therapy when possible, narrowing to the most focused regimen based on culture data 2, 1

Assessing Treatment Response

Clinical Improvement

• Clinical improvement usually takes 48-72 hours
• Do not change therapy during this time unless there is rapid clinical decline 2

Non-Response to Therapy

If patient fails to improve after 72 hours, consider:

• Non-infectious mimics of pneumonia
• Unsuspected or drug-resistant organisms
• Extrapulmonary sites of infection
• Complications of pneumonia 2, 1

Common Pitfalls to Avoid

• Overdiagnosis: Studies show up to 35% of patients treated for HAP may not meet objective radiological criteria 4
• Delayed therapy: Increases mortality 1
• Inadequate initial coverage: Use local antibiograms to guide empiric therapy 1
• Failure to obtain cultures: Always collect respiratory samples before starting antibiotics 1
• Treating colonization: Antibiotic treatment of simple colonization is strongly discouraged 2
• Failure to de-escalate: Continuing broad-spectrum therapy unnecessarily contributes to antibiotic resistance 2