Yes, Moraxella catarrhalis is a common cause of acute sinus infections, particularly in children.
Moraxella catarrhalis accounts for approximately 10-20% of acute bacterial sinusitis cases, making it one of the three most common bacterial pathogens alongside Streptococcus pneumoniae and Haemophilus influenzae 1, 2.
Bacterial Distribution in Acute Sinusitis
The microbiology of acute bacterial sinusitis is well-established through direct maxillary sinus aspiration studies:
- Streptococcus pneumoniae: ~30% of cases
- Haemophilus influenzae: ~30% of cases
- Moraxella catarrhalis: ~10-20% of cases 2
In children specifically, M. catarrhalis represents approximately 20% of acute bacterial sinusitis cases 2, making it relatively more common in pediatric populations than adults.
Key Clinical Context
Important caveat: Most sinus infections are viral, not bacterial 1, 3. Viral upper respiratory infections frequently precede bacterial superinfection by these three organisms 1. Only about 0.5-2% of viral upper respiratory infections progress to acute bacterial sinusitis 3.
Antibiotic Resistance Pattern
Nearly 100% of M. catarrhalis strains produce β-lactamase, making them resistant to amoxicillin alone 2, 4. This is why amoxicillin-clavulanate is preferred over amoxicillin for empiric treatment when bacterial sinusitis is suspected 2, 5.
Chronic vs. Acute Sinusitis
The microbiology shifts in chronic sinusitis. While M. catarrhalis can still be present, Staphylococcus aureus and anaerobic bacteria become the predominant pathogens in chronic disease 1, 6, 7. M. catarrhalis is primarily relevant in acute bacterial sinusitis, not chronic forms.