What antibiotic is recommended for M. catarrhalis and H. influenzae infections?

Antibiotic Treatment for Moraxella catarrhalis and Haemophilus influenzae Infections

For infections caused by Moraxella catarrhalis and Haemophilus influenzae, amoxicillin-clavulanate is the recommended first-line antibiotic treatment due to its excellent coverage against both pathogens, including β-lactamase-producing strains. This recommendation is based on the high prevalence of β-lactamase production in these organisms and the proven efficacy of amoxicillin-clavulanate against these pathogens 1, 2.

Rationale for Antibiotic Selection

Pathogen Characteristics and Resistance Patterns

• M. catarrhalis: 90-100% of strains produce β-lactamase 1, 3
• H. influenzae: 20-35% of strains produce β-lactamase 1, 4

First-line Treatment Options

Amoxicillin-Clavulanate

• Recommended dosage:
  • Adults: 875 mg amoxicillin/125 mg clavulanate twice daily
  • Children: 90 mg/kg/day of amoxicillin with 6.4 mg/kg/day of clavulanate in two divided doses 1, 5
• Advantages:
  • FDA-approved specifically for H. influenzae and M. catarrhalis infections 2
  • Effective against β-lactamase-producing strains
  • Well-established safety profile
  • Readily available and cost-effective

Alternative Treatment Options

For Patients with Penicillin Allergy:

1. Respiratory Fluoroquinolones (adults only)

   • Levofloxacin (500 mg daily) or moxifloxacin (400 mg daily) 1, 5
   • Excellent activity against both pathogens, including β-lactamase producers 6, 7
   • Not approved for use in children

2. Doxycycline

   • Adult dosage: 100 mg twice daily 1, 5
   • Effective against approximately 98% of H. influenzae and M. catarrhalis 1
   • Contraindicated in children under 8 years

3. Second or Third-generation Cephalosporins

   • Cefuroxime axetil (adults: 500 mg twice daily; children: 30 mg/kg/day in 2 divided doses) 1
   • Cefdinir (adults: 300 mg twice daily; children: 14 mg/kg/day in 1-2 doses) 1, 5
   • Both provide good coverage against β-lactamase-producing strains

Antibiotics to Avoid

1. Amoxicillin alone

   • Ineffective against β-lactamase-producing strains of both pathogens 1, 5

2. Macrolides as monotherapy

   • Poor activity against H. influenzae 1, 5
   • Not recommended as first-line therapy

3. Trimethoprim-Sulfamethoxazole

   • High resistance rates (14-33% for H. influenzae, 1.5-50% for M. catarrhalis) 3, 4, 8

Treatment Duration and Monitoring

• Standard treatment duration: 7-10 days 1, 5
• Clinical response should be evident within 48-72 hours of initiating therapy 1
• If no improvement after 72 hours, consider:
  • Alternative antibiotic
  • Obtaining cultures if not already done
  • Evaluating for complications or alternative diagnoses

Special Considerations

Severe Infections

• For severe infections requiring hospitalization, consider:
  • Ceftriaxone 1-2g IV daily 1, 5
  • Switch to oral therapy once clinical improvement is observed

Pediatric Considerations

• High-dose amoxicillin-clavulanate is the preferred treatment for children 1, 5
• For children with non-type I penicillin allergies, cefdinir or cefuroxime are appropriate alternatives 1

Infection Site-Specific Considerations

• For otitis media: High-dose amoxicillin-clavulanate is particularly effective 1
• For sinusitis: Treatment duration may need to be extended to 10-14 days 1
• For lower respiratory tract infections: Consider severity and comorbidities when selecting antibiotics 1

By following these evidence-based recommendations, clinicians can effectively treat infections caused by M. catarrhalis and H. influenzae while minimizing the risk of treatment failure due to antimicrobial resistance.