What is the most common causative agent of nosocomial (hospital-acquired) sinusitis in Intensive Care Unit (ICU) patients?

Most Common Causative Agent in Nosocomial Sinusitis in the ICU

Pseudomonas aeruginosa is the most common causative agent in nosocomial sinusitis in ICU patients, representing approximately 15-29% of isolates. 1, 2

Microbiology of Nosocomial Sinusitis

• Nosocomial sinusitis in ICU patients is typically polymicrobial and predominantly caused by gram-negative bacilli 3, 1
• The most frequently isolated pathogens include:
  • Pseudomonas aeruginosa (15.9-29% of isolates) 1, 2
  • Proteus mirabilis (26% of isolates) 2
  • Acinetobacter baumannii (14% of isolates) 2, 4
  • Staphylococcus aureus (10.6% of isolates) - the most common gram-positive isolate 1
• Fungi represent approximately 8.5% of isolates 1

Pathophysiology and Risk Factors

• Nosocomial sinusitis is a common complication in critically ill patients, particularly those with:
  • Nasotracheal intubation (higher risk than orotracheal intubation) 4
  • Nasogastric tubes 4
  • Head trauma 4
  • Prolonged mechanical ventilation 4
• The presence of these devices can obstruct normal sinus drainage, creating an environment conducive to bacterial growth 3
• Radiographic sinusitis occurs in 25-75% of critically ill patients, with 18-32% of endotracheally intubated patients developing sinusitis 1

Clinical Presentation and Diagnosis

• Clinical features of nosocomial sinusitis in ICU patients are often subtle and may be limited to:
  • Unexplained fever (most common presentation) 3
  • Mucopurulent nasal discharge (may be present) 3
• Diagnosis requires a high index of suspicion in ICU patients with risk factors 3
• Diagnostic approach:
  • CT scan of paranasal sinuses (preferred imaging modality) 1
  • Sinus aspiration for culture and sensitivity testing 3, 1
• Nasal swabs have limited diagnostic value (63% correlation with sinus puncture findings) 2

Treatment Considerations

• Treatment involves:
  • Removal of all nasal tubes when possible 4
  • Sinus drainage and lavage 4
  • Appropriate antimicrobial therapy based on culture results 3
• Antimicrobial resistance is a significant concern:
  • High rates of resistance are observed in isolates from ICU patients with nosocomial sinusitis 2
  • For severe infections with multidrug-resistant Pseudomonas aeruginosa, combination therapy may be necessary 5

Clinical Significance

• Nosocomial sinusitis is associated with increased risk of developing pneumonia 4
• The sinus can serve as a bacterial reservoir from which organisms may seed the tracheobronchial tree 4
• This association is particularly strong with Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii 4

Common Pitfalls

• Failure to consider sinusitis in ICU patients with unexplained fever 3
• Relying on nasal swabs alone for diagnosis (sinus puncture is more reliable) 2
• Discrepancy between radiological findings and actual infection (radiological findings require microbiological confirmation) 3
• Inadequate empiric antimicrobial coverage for Pseudomonas aeruginosa in high-risk patients 5