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Slide 7 Rapid diagnostic tests such as coagglutination and latex agglutination which directly detect soluble bacterial antigens, may be useful. These may provide true positive results when culture and gram stain results are negative and for patients who have already received antimicrobial therapy. Antigen detection methods should never be substituted for culture and gram stain. If only a small amount of CSF is received, gram stain and culture should always have priority over antigen detection tests.

Slide 8 Blood cultures should be obtained in every patient suspected of having bacterial meningitis. A positive blood culture in the presence of signs and symptoms of meningitis would suggest the possible etiologic agent of the meningitis. In patients with otitis media and concomitant meningitis, needle aspiration of middle ear fluid may permit early identification of the likely organism. Cultures from the throat, nasopharynx and urine have not been rewarding and do not correlate with organisms recovered from the CSF or blood.

Slide 9 In cases where lumbar puncture is contraindicated and the anterior fontanel is open, a cranial ultrasound may be useful in detecting the presence of complications of bacterial meningitis such as hydrocephalus, effusion, empyema, malacic changes, ventriculitis or mass lesions. In a local study by Lee, out of 224 cases of bacterial meningitis, 202 had abnormal findings, while 22 patients had normal results. Thus a normal ultrasound does not rule out the presence of meningitis. *Lee, LV et al, Phil J. Neurology 1994; 2:30-38

Slide 10 Meningitis may be diagnosed using CT scan and Magnetic resonance imaging by detecting an increased degree of enhancement and thickening of the meninges beyond the normal range. However, these changes may be subtle and difficult to perceive because of the density of the overlying skull. Nonspecific abnormalities include widening of spaces containing CSF or mild basilar enhancement. In a prospective study by Cabral, et al, out of 41 children with proven bacterial meningitis, only 14 had abnormal CT scan findings. MRI is a far more sensitive imaging technique than CT scan in demonstrating abnormalities of the brain parenchyma and showing changes that affect the meninges. However, meningeal enhancement demonstrated on MRI are nonspecific and is also seen with involvement by a tumor, intracranial hemorrhage, trauma or radiation therapy. Also the use of the MRI is limited by its high cost. Thus these imaging techniques should be considered for patients with signs of increased intracranial pressure prior to obtaining a lumbar puncture, and for patients with persistent neurologic dysfunction (prolonged obtundation, irritability, seizures, focal neurological abnormalities, enlarging head circumference), persistent elevation of CSF protein, persistent preponderance of PMNs in the CSF, or recurrence of disease. *Cabral DA, et al. J Pediatrics 1987; 11:423-32

Slide 11 Bacterial meningitis is a medical emergency that require immediate institution of antimicrobial therapy. Even if a lumbar puncture cannot be performed empirical therapy should be started. The initial regimen chosen should be broad enough to affect all the likely pathogens for the age group involved. Thus local data is essential in order to choose the most appropriate treatment.

Slide 12 Since meningitis is a leading cause of mortality in the Philippines, specially for those less than 5 years old, knowledge of the top CSF isolates in each age group is essential. Unfortunately, studies on etiology specific meningitis is lacking. A study done by Arciaga (1992) showed that H. influenzae and S. pneumoniae were the most common causes in meningitis beyond the neonatal age group. In those less than one year old, gram negative bacilli most common. The incidence of H. influenzae B and S. pneumoniae has probably not changed in the last ten years because immunizations for these two diseases are not routinely given due to their high cost. In contrast to other Western countries, Group B streptococcus is a rare cause of meningitis and Listeria monocytogenes has not been isolated in the CSF even in neonates. In a developing country like the Philippines with limited resources, the most cost effective drug must be chosen.

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