How do you differentiate and treat fungal vs bacterial sinusitis?

Differentiating Fungal vs Bacterial Sinusitis

Bacterial sinusitis and fungal sinusitis present with distinct clinical features that guide diagnosis and treatment approaches, with fungal sinusitis requiring more aggressive intervention, especially in immunocompromised patients.

Clinical Presentation

Bacterial Sinusitis

• Timing: Typically follows upper respiratory tract infection that persists beyond 10-14 days 1
• Key symptoms:
  • Nasal congestion
  • Purulent rhinorrhea
  • Facial-dental pain
  • Postnasal drainage
  • Headache
  • Cough 1
• Clinical signs:
  • Sinus tenderness on palpation
  • Mucosal erythema
  • Purulent nasal secretions
  • Increased pharyngeal secretions 1

Fungal Sinusitis

Fungal sinusitis is classified into three invasive and two non-invasive forms:

Invasive Forms:

1. Acute invasive fungal sinusitis:

   • Occurs primarily in immunocompromised patients (diabetics, leukemia patients, transplant recipients)
   • Presents with fever, headache, epistaxis, mental status changes
   • May have insensate nasal ulcers
   • Can rapidly progress to facial pain, proptosis, ophthalmoplegia, facial necrosis 1
   • Often fatal without prompt treatment 2

2. Chronic invasive fungal sinusitis:

   • Associated with diabetes mellitus and corticosteroid treatment
   • Presents with orbital apex syndrome
   • Shows dense accumulation of hyphae resembling mycetoma 3

3. Granulomatous invasive fungal sinusitis:

   • Patients usually appear immunocompetent
   • Typically presents with proptosis 3

Non-invasive Forms:

1. Allergic fungal sinusitis
2. Fungal ball (mycetoma) 4

Diagnostic Approach

For Bacterial Sinusitis:

1. Clinical history: Focus on duration of symptoms (>10-14 days suggests bacterial infection)
2. Physical examination: Look for purulent rhinorrhea, facial pain, and sinus tenderness
3. Consider imaging: CT scan if complications are suspected

For Fungal Sinusitis:

1. High index of suspicion in immunocompromised patients 2
2. Endoscopic examination: Look for brick red or black necrotic areas 1
3. Biopsy: Essential for diagnosis, with samples sent for fungal staining and culture 1
4. Imaging: CT or MRI to assess extent of disease and invasion 4

Treatment Approaches

Bacterial Sinusitis:

• First-line therapy: Antibiotics based on likely pathogens
  • Common pathogens: Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis
  • Consider resistance patterns (25-50% of S. pneumoniae are penicillin-resistant) 1
• For chronic bacterial sinusitis: Consider S. aureus, gram-negative enteric organisms, and anaerobes 1

Fungal Sinusitis:

• Invasive fungal sinusitis:

  • Surgical debridement: Aggressive and immediate 1
  • Systemic antifungal therapy: Often voriconazole for Aspergillus species 5
  • Hospital admission for IV antifungal therapy may be necessary 2
  • Monitoring: Frequent assessment for disease progression

• Non-invasive fungal sinusitis:

  • Surgical removal of fungal material
  • Antifungal therapy may not be necessary in immunocompetent patients with localized disease 6

Key Distinguishing Features

1. Patient factors: Immunocompromised status strongly suggests possible fungal etiology
2. Progression: Rapid progression with orbital or neurological symptoms suggests invasive fungal disease
3. Appearance: Black necrotic areas on endoscopy are characteristic of invasive fungal sinusitis
4. Biopsy findings: Vascular invasion by fungal elements is diagnostic of invasive fungal disease 3

Common Pitfalls to Avoid

1. Delayed diagnosis: Failing to suspect fungal sinusitis in immunocompromised patients
2. Inadequate sampling: Insufficient biopsy material can lead to false negatives 7
3. Antibiotic overuse: Viral sinusitis (40-90% of cases with CT evidence of sinusitis) resolves without antibiotics within 21 days 1
4. Incomplete treatment: Fungal sinusitis requires both surgical debridement and antifungal therapy in invasive forms

Special Considerations

• Nosocomial sinusitis: Typically caused by gram-negative enterics rather than the usual community-acquired pathogens 1
• Recent antibiotic use: Can alter culture results; stop antibiotics for at least 48 hours before obtaining cultures 7
• Imaging limitations: CT changes consistent with sinusitis are present in up to 90% of viral upper respiratory infections 1