UAB Study Yields New Findings About Bacterial Meningitis

Researchers at UAB (University of Alabama at Birmingham) have discovered a new pathway by which the bacterium Streptococcus pneumoniae (pneumococci), the most common cause of meningitis, pneumonia and inner ear infections, enters the brain, according to a study published recently in the Proceedings of the National Academy of Sciences. Researchers believe this finding could pave the way for the development of a new nasal vaccine to treat pneumococcal infections.

December 2, 2003

Birmingham, Ala. -- Researchers at UAB (University of Alabama at Birmingham) have discovered a new pathway by which the bacterium Streptococcus pneumoniae (pneumococci), the most common cause of meningitis, pneumonia and inner ear infections, enters the brain, according to a study published recently in the Proceedings of the National Academy of Sciences. Researchers believe this finding could pave the way for the development of a new nasal vaccine to treat pneumococcal infections.

“It’s widely assumed that these bacteria, following colonization of the nasal tract, infect the lungs and subsequently travel via the blood stream to the brain,” said Frederik van Ginkel, Ph.D., research assistant professor of microbiology at UAB and lead investigator. “Our findings show bacteria enter the brain directly from the nasal cavity by way of olfactory nerves connecting nasal and brain tissue.”

“This is an extremely important finding about how this deadly infection occurs,” said David Briles, Ph.D., professor of microbiology and co-investigator. “It opens the door for the development of new nasal vaccines that may be more effective and less expensive than the current vaccine.”

Worldwide, pneumococcal infections are a leading cause of death. “There is a high rate of infection, particularly among children,” Briles said. “It’s estimated that up to 30 percent of children in day care centers may be infected by pneumococci in their nasal tract. Although only a few will develop disease, these nasal carriers are important in spreading the bacteria to others. The only way to prevent disease and the spread of pneumococcal infection is to prevent the bacteria from colonizing the nasal cavity. Based on our findings a vaccine that decreases nasal carriage could be a possibility in the future. ”

Researchers learned the bacteria travel directly from the nasal cavity to the brain by way of olfactory nerve cells, which cover a large surface area in the nose. “Gangliosides, complex molecules found on the surface of these nerve cells as well as other cells, are cleaved by an enzyme called neuraminidase produced by pneumococci,” van Ginkel said. “The alteration of gangliosides by this enzyme exposes receptors on the cell surface to which bacteria attach, enabling them to enter nerve cells. These nerve cells then carry the bacteria into the brain.”

UAB researchers already are developing a nasal vaccine. “A nasal vaccine may prove the only effective means of preventing bacteria from colonizing the nasal cavity,” Briles said. “The current vaccine, given by injection, is simply not effective. It’s also costly – too expensive for many in this country and not an option for millions living in developing countries.”

Researchers also learned that, contrary to popular belief, it is not just the occasional bacterium that escapes the nasal cavity to invade the brain. “In infected mice, the brain is continually warding off invading bacteria,” van Ginkel said. “This surprising discovery suggests the brain is quite apt at defending itself from attack.”

Other UAB microbiologists who collaborated on the study are: Jerry McGhee, Ph.D., James Watt, Ph.D., Antonia Campos-Torres, Ph.D., and Lindsay Parish.