NEW ORLEANS - While the incidence of Haemophilus influenzae type b (Hib) meningitis has decreased because of widespread use of conjugate vaccines, rates of meningitis caused by Neisseria meningitidis and Streptococcus pneumoniae remain stable. How to best treat these diseases is not a certainty, and some questions remain about how to best prevent and detect them.
The standard length of antibiotic treatment for bacterial meningitis depends on the underlying cause. For children with meningococcal meningitis, treatment lasts five to seven days. For treatment of Hib meningitis, the recommended duration of antibiotics is seven to 10 days; for pneumococcal meningitis, treatment usually lasts for 10 days.
However, the different durations of treatment may not be needed, said Ellen R. Wald, MD, from the Children's Hospital of Pittsburgh, adding doctors tend to worry more about diseases with more severe consequences, such as S. pneumoniae meningitis, and increase the length of treatment.
Although there is great variation among patients, concentrations of ß-lactam antibiotics in the cerebrospinal fluid (CSF) tend to be greatest in the first three days. The concentration drops to <5% after day seven, explained Wald, a member of the Infectious Diseases in Children editorial advisory board.
Initial drug therapy includes vancomycin and a third-generation cephalosporin to provide antibacterial coverage for the possibility that S. pneumoniae may be resistant to b-lactam antibiotics, said Wald at the 38th Annual Meeting of the Infectious Diseases Society of America held here.
When patients are allergic to ß-lactam antibiotics, alternative regimens include vancomycin and rifampin or meropenem (Merrem, AstraZeneca).
Chemoprophylaxis is not required for children who come in casual contact with the index case, Wald said. Transmission of N. meningitidis requires intimate contact over a long time. Contact among school children is generally not intimate enough to spread the disease.
Prophylaxis should be considered for children who share a bedroom, live in the same household or attend the same nursery school or day care center as the index patient. Children who share meals, toothbrushes or beds may also benefit from chemoprophylaxis.
For pregnant women who have intimate contact with an infected child or who are concerned about transmission, a single dose of ceftriaxone (Rocephin, Roche) is recommended.
Testing for bacterial meningitis can be challenging. A latex agglutination test to detect meningococcal polysaccharide antigens in urine or serum is not very sensitive, Wald said.
"We can diagnose probable N. meningitidis with a positive latex agglutination test of the CSF, a clinical picture and CSF profile that is compatible with meningitis, but we cannot say it's a definite case," Wald said.
Even if a culture does not confirm the diagnosis, but the latex agglutination test in the CSF is positive, switching the patient from broad-spectrum antimicrobials to penicillin is recommended.
"If it's going to be positive, a CSF culture will usually be so within the first 24 hours, but you can't conclude it's negative until 48 or 72 hours. By the end of that time, the patient will most likely have had three days of advanced generation cephalosporins which could clear up the infection," Wald added.
For patients who receive dexamethasone or who are not responding as well as hoped after initial therapy, a repeat lumbar puncture may be indicated. "Some S. pneumoniae are highly resistant and dexamethasone could mask a lack of response in patients infected with these resistant strains," she said. "A second lumbar puncture after one day of therapy can be valuable."
Bacterial meningitis is primarily a childhood disease, with incidence peaking in the first year of life, Wald said. The polysaccharide-coated organisms that cause bacterial meningitis begin to appear at about 3 to 6 months of age, when the maternal antibodies wane. The incidence declines between 2 and 3 years of age.
Epidemics that occur in the military or on college campuses represent secondary peaks. Although the media is often quick to play on the public's fear of meningitis outbreaks, only about 5% of cases of meningococcal disease in the United States are associated with outbreaks. Most cases are sporadic.
For more information:
- Wald ER, Täuber M. Management of meningitis. Meet the Professor session 25. Presented at the 38th Annual Meeting of the Infectious Diseases Society of America. Sept. 7-10, 2000. New Orleans.
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