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

Most Common Causative Agent in Nosocomial Sinusitis in the ICU

Pseudomonas aeruginosa is the most common causative agent in nosocomial sinusitis in the ICU. 1, 2, 3, 4

Microbiology of Nosocomial Sinusitis

The microbiology of nosocomial sinusitis differs significantly from community-acquired sinusitis, with gram-negative organisms predominating in the hospital setting, particularly in critically ill patients:

Primary Pathogens

• Pseudomonas aeruginosa: Consistently identified as the most common pathogen, representing 15-29% of isolates 2, 4
• Gram-negative enterics:
  • Acinetobacter baumannii
  • Proteus mirabilis
  • Klebsiella pneumoniae
  • Enterobacter species
  • Serratia marcescens
• Gram-positive cocci:
  • Staphylococcus aureus (second most common pathogen)

Microbiological Profile

• Often polymicrobial infections 5
• Anaerobes and fungi may be present as co-pathogens
• Streptococcus pneumoniae and Haemophilus influenzae (common in community-acquired sinusitis) are far less frequently isolated in nosocomial cases 5

Risk Factors for Nosocomial Sinusitis in ICU

Several factors contribute to the development of nosocomial sinusitis in ICU patients:

• Mechanical ventilation (especially prolonged)
• Nasotracheal intubation (higher risk than orotracheal)
• Nasogastric tubes
• Head trauma
• Prolonged ICU stay
• Impaired consciousness
• Immunosuppression

Diagnostic Considerations

Diagnosis of nosocomial sinusitis requires:

• CT scan of paranasal sinuses (gold standard imaging)
• Maxillary sinus puncture for microbiological confirmation
  • Nasal swabs have limited diagnostic value (63% correlation with sinus puncture) 2
  • Quantitative cultures should be performed (infection is documented when bacterial species is recovered at ≥10³-10⁴ CFU/mL) 1

Clinical Significance

Nosocomial sinusitis in ICU patients:

• Often underdiagnosed due to lack of specific clinical signs
• Associated with increased risk of ventilator-associated pneumonia 3
• Serves as a bacterial reservoir that may seed the tracheobronchial tree
• Particularly concerning when caused by multidrug-resistant organisms

Treatment Approach

Treatment should include:

• Removal of all nasal tubes when possible
• Sinus drainage and lavage
• Appropriate antibiotic therapy based on culture results
• Consideration of high resistance patterns (particularly with Pseudomonas aeruginosa)

Answer to Multiple Choice Question

The correct answer is A. Pseudomonas aeruginosa, which is consistently identified as the most common causative agent in nosocomial sinusitis in ICU patients across multiple studies.