Treatment of Haemophilus influenzae Meningitis
For H. influenzae meningitis, third-generation cephalosporins (ceftriaxone or cefotaxime) are the drugs of choice, administered for 10 days in adults and 7-10 days in children who recover rapidly. 1
Definitive Antimicrobial Therapy
Adult Patients
Once H. influenzae is identified, continue ceftriaxone 2 grams IV every 12 hours or cefotaxime 2 grams IV every 6 hours for 10 days. 1
- Alternative therapy includes cefepime, chloramphenicol, fluoroquinolones, or meropenem if third-generation cephalosporins cannot be used 1
- Moxifloxacin 400 mg once daily is an acceptable alternative for patients with cephalosporin allergy 1
Pediatric Patients (≥3 months of age)
For children weighing <50 kg, administer ceftriaxone 50 mg/kg every 12 hours (maximum 2 grams every 12 hours) or cefotaxime 75 mg/kg every 6-8 hours. 1
- Children weighing ≥50 kg should receive adult dosing: ceftriaxone 2 grams IV every 12 hours 1
- Meropenem 40 mg/kg every 8 hours (maximum 2 grams every 8 hours) is FDA-approved for H. influenzae meningitis in children ≥3 months and represents an important alternative. 2
Treatment Duration
Treatment can be discontinued after 7 days in children with rapid initial recovery (defined by absence of fever, normal clinical signs, and normalized C-reactive protein by day 4-5). 3
- Standard duration is 10 days for adults and 7-10 days for children 1, 4
- Treatment duration may need extension if the patient is not responding adequately 1
Empirical Therapy Considerations
β-Lactamase Production
The emergence of β-lactamase-producing H. influenzae strains has made third-generation cephalosporins essential for empirical therapy, as these organisms are resistant to ampicillin. 1
- If β-lactamase-negative H. influenzae is confirmed by susceptibility testing, ampicillin can be used as an alternative 1
- Third-generation cephalosporins have proven superior to chloramphenicol and second-generation cephalosporins (cefuroxime) in clinical trials 1
Age-Specific Empirical Regimens
For infants <3 months of age, use ampicillin plus cefotaxime (not ceftriaxone due to bilirubin displacement concerns) until H. influenzae is confirmed. 1, 5
- Cefotaxime dosing for neonates 1-4 weeks: 50 mg/kg every 6-8 hours 1
- Ceftriaxone should be avoided in neonates due to risk of kernicterus 5
Adjunctive Dexamethasone Therapy
Adjunctive dexamethasone (0.15 mg/kg every 6 hours for 2-4 days) should be administered with or before the first antibiotic dose in children with suspected or proven H. influenzae meningitis. 1
- Dexamethasone has confirmed benefit for H. influenzae type b meningitis, particularly for preventing hearing impairment (combined OR 0.31; 95% CI 0.14-0.69) 1
- The first dexamethasone dose must be given 10-20 minutes before or concomitant with antibiotics to be effective 1
Critical Pitfalls to Avoid
Never use ampicillin alone for empirical therapy of suspected H. influenzae meningitis, as 20-40% of strains produce β-lactamase and are resistant. 1, 6
- Do not use second-generation cephalosporins (cefuroxime), as they have inferior CSF penetration and clinical outcomes compared to third-generation agents 1
- Avoid imipenem due to 33% seizure risk in children with bacterial meningitis 1
- Do not discontinue therapy prematurely—ensure at least 7 days of treatment even in rapidly recovering patients 3
Monitoring and Follow-up
Perform hearing assessment post-therapy, as 20-30% of patients develop some degree of hearing loss despite appropriate treatment. 2
- CSF sterilization typically occurs within 24 hours of initiating third-generation cephalosporins 3, 5
- Clinical improvement should be evident by day 2-3; if not, consider repeat lumbar puncture to assess treatment response 7
Chemoprophylaxis
Administer rifampin prophylaxis to close contacts of H. influenzae meningitis cases to prevent secondary transmission. 4