What is the recommended treatment for Moraxella (Moraxella catarrhalis) bacteria in an 8-year-old child allergic to Penicillin (PCN)?

Treatment of Moraxella catarrhalis in an 8-year-old with Penicillin Allergy

For an 8-year-old child with Moraxella catarrhalis infection who is allergic to penicillin, a macrolide antibiotic such as azithromycin or a cephalosporin such as cefdinir is recommended as first-line therapy, depending on the type of penicillin allergy and site of infection.

Understanding Moraxella catarrhalis

• Moraxella catarrhalis is a common respiratory pathogen in children, causing otitis media, sinusitis, and lower respiratory tract infections 1, 2
• Over 80% of M. catarrhalis strains produce beta-lactamase, making them resistant to penicillin and ampicillin 3, 2
• M. catarrhalis remains highly susceptible to macrolides, cephalosporins, and trimethoprim-sulfamethoxazole 1, 3

Treatment Options Based on Penicillin Allergy Type

For Non-Immediate/Non-Anaphylactic Penicillin Allergy:

1. Cephalosporins (First Choice)

   • Cefdinir: 14 mg/kg/day divided in 1-2 doses (maximum 600 mg/day) 4
   • Cefdinir is FDA-approved for treatment of infections caused by M. catarrhalis, including respiratory infections 4
   • Alternative cephalosporins: cefpodoxime, cefuroxime, or cefprozil 5

2. Monitoring:

   • Assess clinical response within 72 hours 5
   • If no improvement after 72 hours, consider alternative therapy or reevaluation 5

For Immediate/Anaphylactic Penicillin Allergy:

1. Macrolides (First Choice)

   • Azithromycin: 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg (maximum 250 mg) once daily on days 2-5 6
   • Alternative: Clarithromycin 15 mg/kg/day in 2 doses (maximum 1 g/day) 5

2. Alternative Options:

   • Trimethoprim-sulfamethoxazole: 8-12 mg/kg/day (based on trimethoprim component) in 2 divided doses 5
   • Clindamycin: 10-20 mg/kg/day in 3 divided doses (if susceptibility confirmed) 5

Treatment Considerations by Infection Site

For Otitis Media

• Azithromycin is effective against M. catarrhalis in otitis media with documented eradication rates of 100% at day 10 and 100% at days 24-28 6
• Cefdinir is FDA-approved for acute bacterial otitis media caused by M. catarrhalis 4

For Sinusitis

• Azithromycin has demonstrated clinical success rates of 93% at day 7 and 87% at day 28 for M. catarrhalis in sinusitis 6
• For children with moderate sinusitis and penicillin allergy, cefdinir is preferred due to high patient acceptance 5

For Lower Respiratory Tract Infections

• Azithromycin or clarithromycin for presumed atypical pneumonia 5
• Cefdinir is FDA-approved for community-acquired pneumonia caused by M. catarrhalis 4

Important Clinical Considerations

• M. catarrhalis infections are more common in fall through early spring 7
• For children with immediate hypersensitivity reactions to β-lactams, desensitization may be considered in severe cases where cephalosporins are contraindicated 5
• Approximately 10% of penicillin-allergic patients may also be allergic to cephalosporins, so caution is needed when using cephalosporins in these patients 5
• Treatment duration typically ranges from 5 days for azithromycin to 10 days for other antibiotics 5, 6

Monitoring and Follow-up

• Assess clinical response within 48-72 hours of initiating therapy 5
• If no improvement occurs after 72 hours, consider:
  1. Switching to an alternative antibiotic class
  2. Obtaining cultures to confirm susceptibility
  3. Reevaluating the diagnosis 5