Haemophilus influenzae: Signs and Treatment
Haemophilus influenzae infections require prompt recognition and treatment with appropriate antibiotics, with co-amoxiclav or a tetracycline being the preferred first-line treatments for most presentations in adults. 1
Clinical Presentations and Signs
H. influenzae can cause two distinct patterns of infection:
Invasive Disease
- Meningitis: Fever, headache, neck stiffness, altered mental status
- Epiglottitis: Rapid onset of sore throat, difficulty swallowing, drooling, respiratory distress
- Septic arthritis: Joint pain, swelling, limited mobility, fever
- Cellulitis: Typically facial or periorbital in children, with erythema and swelling
- Bacteremia: High fever, chills, malaise, tachycardia
Non-invasive/Respiratory Disease
- Pneumonia: Fever, productive cough, dyspnea, chest pain
- Acute otitis media: Ear pain, fever, hearing loss
- Sinusitis: Facial pain/pressure, nasal discharge, headache
- Acute bronchitis: Cough, sputum production, wheezing
Diagnosis
- Gram stain of appropriate specimens may show small gram-negative coccobacilli
- Culture on chocolate agar (blood and other normally sterile fluids)
- Detection of capsular antigen in serum, CSF or urine using immunoelectrophoresis, latex agglutination or ELISA 2
- Blood cultures are essential for suspected invasive disease
Treatment Guidelines
Adults with Non-Severe Infections (Outpatient)
First-line options:
- Co-amoxiclav 500-875 mg orally twice daily for 7 days 1
- Doxycycline 100 mg orally twice daily for 7 days 1
Alternative options (for penicillin allergy):
- Clarithromycin 500 mg orally twice daily for 7 days 1
- Erythromycin 500 mg orally four times daily for 7 days 1
Adults with Severe Infections (Requiring Hospitalization)
First-line options:
- IV co-amoxiclav 1.2 g every 8 hours 1
- IV cefuroxime 750-1500 mg every 8 hours 1
- IV cefotaxime 1-2 g every 8 hours 1
- IV ceftriaxone 1-2 g daily 3
For severe pneumonia, combination therapy:
- IV broad-spectrum β-lactamase stable antibiotic (co-amoxiclav or cephalosporin) PLUS
- IV macrolide (clarithromycin or erythromycin) 1
Children with H. influenzae Infections
First-line for children <12 years:
- Co-amoxiclav (dose adjusted by weight) 1
Alternatives for penicillin allergy:
- Clarithromycin or cefuroxime 1
For children >12 years:
- Doxycycline is an alternative 1
Meningitis Treatment
Special Considerations
Antibiotic Prophylaxis
- Indicated for household contacts when there is a vulnerable individual (child <10 years or immunosuppressed/asplenic person)
- Rifampicin 20 mg/kg/day for 4 days is recommended for prophylaxis 4
Vaccination
- Hib vaccination is crucial for prevention
- All children should receive Hib vaccine as part of routine immunization
- Patients with functional or anatomic asplenia should receive Hib vaccine if not previously immunized 1
Post-Exposure Management
- Children under 10 years who develop invasive Hib disease should receive rifampicin chemoprophylaxis to eliminate carriage
- Hib antibody levels should be tested about four weeks after infection 4
Monitoring and Response Assessment
- Assess clinical response within 48-72 hours after initiating treatment
- For hospitalized patients with pneumonia, improvement in fever and respiratory symptoms should be evident within 2-3 days 1
- Patients initially treated with parenteral antibiotics should be switched to oral therapy once clinically improved and afebrile for 24 hours 1
Treatment Failure
- For non-severe pneumonia not responding to initial therapy, consider switching to a fluoroquinolone with pneumococcal and staphylococcal coverage 1
- Consider additional investigations including imaging and cultures if no response to appropriate therapy
Remember that early recognition and prompt antibiotic treatment are essential to reduce morbidity and mortality, especially for invasive H. influenzae infections.