Scheld, who presented an overview of bacterial meningitis at the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy here, noted that during the same 10-year period there was more than a 95% decrease in Haemophilus influenzae meningitis in children. "Some people are even talking about the potential elimination of [H. influenzae meningitis] in the United States," he said.
Yet pneumococcal meningitis remains a major challenge and can still lead to death. Among the serogroups responsible for invasive meningococcal disease in the United States in 1995, serogroup C caused about 35% of cases, B about 25%, Y about 30% and A was extremely rare. This breakdown is "much different than in the late 1980s, when serogroup B was about 50%, C about 25% and Y was very unusual," Scheld said.
The current regimen of choice for treating bacterial meningitis is a third-generation cephalosporin, along with vancomycin. "I would not rely on vancomycin alone," said Scheld. An alternative drug is meropenem (Merrem, Zeneca). "This drug has been evaluated in a very large number of patients with bacterial meningitis around the world. It is licensed in the United States and approved for pediatric meningitis, but not yet for adult."
Meropenem is appealing because it is active against most penicillin-resistant pneumococci and the other major meningopathogens, as well as combating Listeria monocytogenes. "So theoretically you could use a single drug," Scheld explained. "But I'm reluctant to recommend meropenem as first-line therapy until we have more information, especially published information."
The most interesting aspect of meningitis research is in mechanisms of neuronal injury. "There is growing evidence that there is a combination of reactive oxygen and nitrogen species, including nitric oxygen," said Scheld. "Toxic amino acids are also being studied."
One of the new diagnostic tests on the horizon for several forms of bacterial meningitis is polymerase chain reaction (PCR). "New diagnostic techniques are potentially going to make the differentiation between viral and bacterial meningitis easier," Scheld noted. "In the normal patient, the real use for PCR at the present time is in the diagnosis of difficult infections, like tuberculous meningitis or perhaps Lyme disease in the central nervous system."
In the future, Scheld predicts an increased focus on different antibiotics, other adjunctive treatments and new vaccines. Dexamethasone as adjunctive treatment is also advantageous; however, "it either needs to be given before or simultaneously with the first dose of an antimicrobial agent."
Scheld noted that one recent trial showed a "very dramatic effect on the reduction of pneumococcal bacteremia" in children given the pneumococcal conjugate vaccine. "It would be a major breakthrough if we had this kind of vaccine for use at 2, 4 and 6 months of age to prevent invasive pneumococcal disease."
For your information:
- Scheld WM. Bacterial meningitis. Presented at the 38th Interscience Conference on Antimicrobial Agents and Chemotherapy. Sept. 24-27. San Diego.