Overview
Definition:
Haemophilus influenzae type b (Hib) is a Gram-negative bacterium that was historically a leading cause of bacterial meningitis, epiglottitis, pneumonia, and sepsis in young children worldwide
The introduction of highly effective Hib conjugate vaccines has dramatically reduced the incidence of invasive Hib disease, but it remains an important pathogen, particularly in unvaccinated or under-vaccinated populations, and can still cause disease in the post-vaccination era.
Epidemiology:
Prior to widespread vaccination, Hib caused an estimated 3 million severe infections and 386,000 deaths annually globally, primarily in children under 5 years
Following the introduction of Hib conjugate vaccines in developed countries in the 1990s, invasive Hib disease incidence has decreased by >95%
However, disease incidence varies significantly in regions with lower vaccination coverage
Outbreaks can occur in pockets of unvaccinated individuals or due to vaccine failure, which is rare but possible.
Clinical Significance:
Despite dramatic reductions, Hib remains a significant cause of potentially life-threatening infections in children
Understanding its clinical presentation, diagnostic approach, and management is crucial for all pediatricians and residents preparing for DNB and NEET SS examinations
Recognizing the nuances of breakthrough infections and the importance of maintaining high vaccination rates are key
The sequelae of untreated or inadequately treated Hib infections, such as neurological deficits, can be devastating.
Clinical Presentation
Symptoms:
Fever, often high-grade
Irritability and lethargy
Vomiting
Poor feeding or refusal to feed
Seizures
Stiff neck and photophobia (meningitis)
Drooling, stridor, and respiratory distress (epiglottitis)
Sore throat and dysphagia
Skin rash (meningococcemia-like or petechial)
Swollen joints or bone pain (septic arthritis/osteomyelitis).
Signs:
Tachycardia and tachypnea
Altered mental status, ranging from somnolence to coma
Nuchal rigidity and positive Kernig's/Brudzinski's signs (meningitis)
Cherry-red epiglottis on direct visualization (epiglottitis) - this is a medical emergency and visualization should be done with extreme caution and preparedness
Drooling, tripod position
Petechial or purpuric rash
Localized swelling, erythema, and tenderness over affected joints or bones.
Diagnostic Criteria:
Diagnosis is typically made by identifying H
influenzae type b from normally sterile body sites such as blood or cerebrospinal fluid (CSF) via culture, antigen detection tests, or PCR
Clinical suspicion is high in children presenting with compatible symptoms, especially if unvaccinated or under-vaccinated
Specific diagnostic criteria are not formally established but are based on isolation of the organism from a sterile site in the context of suggestive clinical illness.
Diagnostic Approach
History Taking:
Detailed history of vaccination status is paramount
inquire about the number of Hib vaccine doses received and the timing
Assess the onset and progression of symptoms
Note any recent illnesses, such as upper respiratory tract infections
Inquire about sick contacts
Family history of invasive bacterial infections
Presence of immunocompromise or underlying medical conditions.
Physical Examination:
Comprehensive physical examination including vital signs
Neurological assessment for signs of meningitis or encephalitis
Thorough examination of the oropharynx for signs of epiglottitis
Assessment for respiratory distress
Examination of skin for rash
Palpation of joints and limbs for signs of septic arthritis or osteomyelitis
Abdominal examination.
Investigations:
Blood cultures: essential for identifying bacteremia
Cerebrospinal fluid (CSF) analysis: cell count, differential, protein, glucose, Gram stain, culture, and PCR for H
influenzae type b
Rapid antigen detection tests for CSF or urine: can provide quick results but are less sensitive and specific than culture/PCR
Complete blood count (CBC) with differential: leukocytosis is common
Chest X-ray: may show pneumonia or pleural effusion
Imaging of affected bones/joints: X-rays, ultrasound, CT, or MRI may be indicated for suspected osteomyelitis or septic arthritis.
Differential Diagnosis:
Other causes of bacterial meningitis (e.g., Streptococcus pneumoniae, Neisseria meningitidis, group B Streptococcus in neonates)
Viral meningitis or encephalitis
Other causes of epiglottitis (e.g., Streptococcus pyogenes, Staphylococcus aureus)
Pneumonia due to other bacterial or viral pathogens
Septic arthritis or osteomyelitis due to other bacteria
Sepsis of unknown origin.
Management
Initial Management:
Immediate referral to a hospital
Prompt administration of broad-spectrum intravenous antibiotics
If epiglottitis is suspected, secure airway management is the priority
intubation should be readily available
Fluid resuscitation if signs of shock are present
Oxygen therapy as needed.
Medical Management:
Antibiotic therapy: Ceftriaxone is the drug of choice for susceptible strains, typically given intravenously at 100 mg/kg/day in two divided doses (max 4 g/day) for meningitis, 75-100 mg/kg/day for other severe infections
Duration of therapy is typically 7-10 days for meningitis, 5-7 days for other infections, adjusted based on clinical response
Dexamethasone may be administered prior to or with the first dose of antibiotics in cases of bacterial meningitis to reduce inflammation and neurological sequelae
dosage is 0.6 mg/kg/day divided into four doses for 2-4 days.
Surgical Management:
Rarely required for invasive Hib disease
May be indicated for complications such as brain abscess requiring drainage or significant joint effusion requiring aspiration/drainage for septic arthritis
Airway management for epiglottitis is critical and may involve intubation or, in rare, severe cases, tracheostomy.
Supportive Care:
Close monitoring of vital signs and neurological status
Management of seizures
Nutritional support, including intravenous fluids and, as tolerated, oral feeding
Pain management
Isolation precautions for suspected meningitis until 24 hours after initiation of effective antibiotics
Prophylaxis with rifampicin for close contacts of patients with invasive Hib disease to reduce secondary transmission.
Complications
Early Complications:
Neurological sequelae from meningitis: hearing loss, developmental delay, intellectual disability, seizures
Airway obstruction from epiglottitis
Sepsis with shock and disseminated intravascular coagulation (DIC)
Osteomyelitis or septic arthritis with joint destruction.
Late Complications:
Chronic neurological deficits
Recurrent infections
Growth impairment.
Prevention Strategies:
Widespread immunization with Hib conjugate vaccines is the most effective preventive strategy
Ensuring high vaccination coverage rates in the population
Post-exposure prophylaxis with rifampicin for unvaccinated close contacts of individuals with invasive Hib disease
Public health awareness campaigns promoting vaccination.
Prognosis
Factors Affecting Prognosis:
Age at onset (younger children generally have worse prognosis)
Severity of illness at presentation
Promptness of diagnosis and initiation of appropriate treatment
Presence of complications such as seizures, shock, or DIC
Underlying host immune status.
Outcomes:
With prompt and appropriate treatment, the fatality rate for invasive Hib disease has significantly decreased, especially in vaccinated populations
However, a substantial proportion of survivors, particularly those who experienced meningitis, may have long-term sequelae
Early recognition and aggressive management improve outcomes significantly.
Follow Up:
Patients who have recovered from invasive Hib disease require careful follow-up to monitor for neurological development, hearing, and overall growth
Audiology and neurodevelopmental assessments are crucial for children who had meningitis
Long-term surveillance for vaccine-preventable diseases and adherence to immunization schedules are essential.
Key Points
Exam Focus:
Focus on the dramatic impact of Hib conjugate vaccines
Understand the typical clinical presentations of meningitis and epiglottitis caused by Hib
Know the key investigations: CSF analysis, blood cultures, and PCR
Recognize ceftriaxone as the drug of choice and the role of dexamethasone in meningitis
Emphasize prophylaxis for close contacts.
Clinical Pearls:
Always check vaccination status for any child presenting with fever and signs of severe illness
High index of suspicion for epiglottitis in a child with stridor and drooling
prepare for airway intervention
Don't delay antibiotics in suspected bacterial meningitis
Remember rifampicin prophylaxis for close contacts to prevent secondary cases.
Common Mistakes:
Underestimating the severity of Hib infections, especially in the post-vaccination era
Delaying empirical antibiotic treatment while awaiting culture results
Inadequate airway preparedness for suspected epiglottitis
Failing to consider post-exposure prophylaxis for unvaccinated contacts.