Bacterial meningitis is a rare disease and it affects children of age younger than 2 years.
Meningitis most commonly presents with subtle signs and symptoms.
1. Etiology of Bacterial Meningitis
– 0 to 3 Months of Age
The most common bacterial agents responsible for infection in infants 0 to 3 months of life (in declining order of frequency) are:
- group B Streptococcus (GBS),
- Escherichia coli,
- Gram-negative enteric bacilli other than E coli,
- fungi, and
The preterm infant is considered an immunocompromised host and thus, all agents should be considered, including bacteria,viruses,Mycoplasma,Ureaplasma, and fungi, as potential causes of infection in this group.
Period of Infancy
– 3 Months to 3 Years
Since the advent of the Haemophilus conjugate vaccines, the principal causes of bacterial meningitis in this age group are N meningitidis and S pneumoniae.
– 3 to 21 Years
The most common bacterial agents for meningitis in this age group are N meningitidis and S pneumoniae. Viral meningitis,principallycaused bythe enteroviruses, arboviruses and herpesviruses, account for most of the disease in this age group.
2. Clinical evaluation
Signs and symptoms of meningitis include fever, headache, neck pain or stiffness, nausea, vomiting, photophobia, and irritability. Young infants may exhibit only signs of irritability, and low-grade fever.
Physical findings include lethargy, somnolence, stiff neck, rash, petechia, purpura,and hemodynamic instability.
Lumbar puncture remains the most important early diagnostic test.
Rapid antigen testing of the CSF and urine are specific but not sensitive indicators of disease, and with the exception of Haemophilus meningitis, it rarely provides helpful information in guiding initial therapy.
Gram stain of a CSF smear is very helpful. CSF protein levels greater than 100 to 120 mg/dL are suggestive of bacterial meningitis, but these also can be seen in congenital infection, tuberculous meningitis, and rarely, in viral CNS disease.
The standard for diagnosis of meningitis remains a positive culture taken before initiation of antibiotic therapy.
Blood culture, Gram stain of a CSF smear, CSF culture, urinalysis, and urine culture should be performed routinely in all children who are suspected clinically of having meningitis. If the CSF indices suggest viral,fungal, ortuberculous disease, specific stains and cultures should be requested.
CSF analysis must include cell count, differential, and protein and glucose concentrations.
When viral meningitis is suspected, rectal swabs, CSF and peripheral buffy coat viral cultures, and PCR should be considered. Isolation of virus from any site suggests the possibility of viral meningitis if the CSF indices are abnormal, but coinfection with bacteria can occur. For the immunocompromised patient, cryptococcal antigen or an India ink-stained smear of CSF provides quick identification.
Complete blood count, platelet count, and serum electrolyte concentrations are helpful as baseline studies. Liver enzymes can be greatlyelevated with enterovirus and disseminated herpetic infection.
3. Management of bacterial meningitis
Term infants in the first month of life are treated with a combination of ampicillin with either gentamicin or cefotaxime. For low-birth weight preterm infants in the nursery who present with late-onset meningitis, an antistaphylococcal agent such as methicillin or vancomycin and an aminoglycoside are used until culture results are available.
Infants 1 to 2 months of age are treated with ampicillin and cefotaxime or ampicillin and ceftriaxone, which provide coverage against enterococci and Listeria as well as the normal pathogens beyond the newborn period.
Infants and children older than 2 months of age : Resistant strains of S pneumoniae have become a major problem. Initial meningitis therapy must include vancomycin in dosages of 60 mg/kg per day in four divided doses in addition to either cefotaxime or ceftriaxone.
Dexamethasone : If CSF indices suggest bacterial meningitis or if organisms are seen on Gram stain ofa CSF smear, dexamethasone is recommended in a dosage of 0.6 mg/kg per day in two to four divided doses for 2 to 4 days. The initial dose of steroid should be infused before the initial dose of parenteral antibiotics.