In developed countries the diagnosis of bacterial meningitis benefits from several tools; for example the measurement of serum or cerebrospinal fluid (CSF) C Reactive Protein, CSF lactates, CSF interleukins (Il) IL-6, IL-8, CSF lactoferrin, tumor necrosis factor alpha (TNF alpha), plasma procalcitonin, CSF nitrates and nitrites (4-19), in addition to the classical CSF gram staining and culture.

Less developed countries lag far behind in terms of general public health policies and have therefore higher mortality and morbidity rates. The reasons for this are multiple; late diagnosis (children being brought too late to hospitals or primary health centers), insufficient diagnostic tools (poorly equipped or non-existent laboratories), expensive and unaffordable antibiotics such as the third generation cephalosporins for example.

Meningitis develops when bacterial pathogenic virulence factors overcome host defense mechanisms. The most common bacteria (Streptococcus pneumoniae, Heamophilus influenzae, Nisseria meningitidis, Esherichia coli, Streptococcus agalactiae (Group B Streptococci)) have a certain ability to evade the host natural defenses by developing evasion mechanisms that help in overcoming each of the barriers (20). Slide I summarizes these evasion mechanisms. Meningitis is therefore a result of the colonization of mucosal epithelium > Bacterial invasion and survival in the intravascular space > Crossing of blood-brain barrier > Survival in the CSF

Knowledge of the epidemiological features of a disease is necessary because choices of adequate treatment, which are often presumptive, and definition of health policies are both based on it. Studies (21-23) have brought certain global evidences: male children are more affected than female with a male to female ratio around 1.5:1, there is a seasonal trend with most cases of bacterial meningitis occurring during fall and winter, however viral cases are more frequent in summer. The commonest causes of bacterial meningitis are shown in Slide 2.

Before the use of H. influenzae type b (Hib) vaccination in the western countries, cases of bacterial meningitis were most commonly caused by H. influenzae (Children aged < 5 years), N. meningitidis, and S. pneumoniae. Peltola (24) calculated that prior to the use of Hib vaccination there were 357,000 cases of H. influenzae meningitis worldwide with a mortality rate around 108,500 in children aged <5 years. The incidence of cases due to H. influenzae have been decreased by 85 to 90% since the introduction of Hib vaccination; this has placed N. meningitidis as the leading organism followed by S. pneumoniae and H. influenzae.

In Africa, S. pneumoniae is the leading cause followed by N. meningitidis serotype A and H. influenzae. Predisposing factors in black populations are Sickle cell disease and high sensibility to S. pneumoniae invasive infections, etc. For all developing countries Hib vaccination is more than needed as young infants and children loose their natural immunity against H. influenzae received from their mothers by the age of twenty months (25).

Presenting symptoms vary in children with age at onset, one must distinguish following age groups: the newborn (from birth to one month of age), infant (2 months to 2 years) and children over two years of age.

(1) The Newborn and Infant

Signs and symptoms are not specific: the infant may have fever (>38 °C), refuse to feed or feed poorly, be hypotonic, irritable with unusual cry, sleepy or inactive, have bulging anterior fontanelle, present with vomiting. With disease progression seizures may occur, this is the case for 40 % of newborn babies. Premature babies as well as those born at term may have cold extremities, temperature instability (hypo or hyperthermia), apnea, respiratory distress, and listlessness as early symptoms.

(2) The older child (>2years)

More than 85% of children with meningitis have the classic triad of fever, headache and neck stiffness (Slide 3). Papilloedema occurs in only 1% of patients during the acute phase, its presence should suggest an alternative method of diagnosis. Computed head scan should be sought before lumbar puncture and the child started on antibiotics to avoid any delay.