Treatment of Sinusitis Caused by Moraxella catarrhalis

First-Line Antibiotic Selection

The American Academy of Otolaryngology-Head and Neck Surgery recommends amoxicillin-clavulanate as the preferred agent for adults with sinusitis caused by Moraxella catarrhalis, due to its effectiveness against beta-lactamase-producing strains 4, 5, 6
The American Academy of Otolaryngology-Head and Neck Surgery suggests that high-dose amoxicillin-clavulanate (90 mg/6.4 mg per kg per day) is the first-line choice for pediatric patients with sinusitis caused by Moraxella catarrhalis, accounting for the fact that nearly 100% of M. catarrhalis isolates are beta-lactamase positive and nonsusceptible to amoxicillin alone 5, 7
Treatment duration is 5-7 days for uncomplicated cases, which is as effective as 10 days with fewer adverse effects 6

For adults with a true penicillin allergy, the American Academy of Otolaryngology-Head and Neck Surgery recommends levofloxacin 500 mg once daily for 5-10 days as a preferred alternative 6
The American Academy of Otolaryngology-Head and Neck Surgery suggests that moxifloxacin 400 mg once daily for 5-10 days is equally effective for adults with a true penicillin allergy 6
Cefuroxime axetil or cefprozil provide significantly enhanced activity against beta-lactamase-producing M. catarrhalis with twice-daily dosing, and are appropriate for non-Type I hypersensitivity reactions to penicillin 1, 2, 5, 7

The American Academy of Otolaryngology-Head and Neck Surgery advises against using plain amoxicillin due to its ineffectiveness against 90-100% of M. catarrhalis strains that produce beta-lactamase 1, 2, 3
First-generation cephalosporins (cephalexin, cefadroxil) have poor coverage for M. catarrhalis and should be avoided 1, 2
Cefaclor has inadequate activity against all beta-lactamase-producing M. catarrhalis and is associated with a high risk of serum sickness-like reactions, making it an unsuitable choice 1, 2
Azithromycin or clarithromycin have predicted clinical efficacy of only 77-81% with bacterial failure rates of 20-25% possible, and should not be used as first-line therapy 5, 8

If symptoms fail to improve or worsen within 72 hours, the American Academy of Otolaryngology-Head and Neck Surgery recommends switching to an alternative antibiotic class, such as a respiratory fluoroquinolone (levofloxacin or moxifloxacin) 5, 6
Consider using ceftriaxone 1 g IM/IV daily for 5 days as an alternative therapy 5

The American Academy of Otolaryngology-Head and Neck Surgery advises against prescribing fluoroquinolones as first-line therapy for uncomplicated cases to prevent promoting resistance, and recommends reserving them for treatment failures or true penicillin allergy 6, 8
Plain amoxicillin should not be used, even at high doses, as beta-lactamase production cannot be overcome by dose escalation 1, 2, 3
Recent antibiotic use within 4-6 weeks, age >65 years or <2 years, diabetes or chronic comorbidities, immunocompromised status, and close contact with daycare children are risk factors that require high-dose therapy 4, 5, 7