Bacterial meningitis is one of the most dangerous types of bacterial diseases. It causes inflammation of the brain or central nervous system, and can cause irreparable damage in those who survive an aggressive infection. When left untreated, bacterial meningitis has a fatality rate as high as 70%, and nearly a quarter of patients who survive the infection are left with severe, permanent neurological complications.
The most common cause of bacterial meningitis is pneumococcal bacteria, an infectious organism that can also cause respiratory infections such as pneumonia. Thanks to immunologists and medical research, vaccines exist that effectively target the most common strains of pneumococcal bacteria. Unfortunately, a new study suggests that those existing vaccines may be potentially ineffective against a different type of pneumococcal bacteria; one that seems to be causing cases of meningitis in an unexpected way.
The study, which was published in The Pediatric Infectious Disease Journal, noted that the use of vaccines has resulted in a greatly decreased rate of pneumonia and bacterial blood infections. However, the rate of bacterial meningitis has not seen a similar decrease and may have, in fact, increased during the same time frame. The study’s authors believe the problem stems from new vaccine-resistant strains of bacteria that have evolved since vaccines have been in broad use.
Hiding from Vaccines – The Bacterial Meningitis Vaccine Challenges
Pneumococcal conjugate vaccines (PCVs) target strains of streptococcus pneumoniae bacteria that are covered by a protective capsule that prevents the body’s immune system from effectively fighting the bacteria in the bloodstream. New strains of bacteria, however, are covered by a different type of capsule that current vaccines can’t penetrate.
“Widespread use of vaccines resulted in the emergence of a broad diversity of replacement non-PCV type strains,” said Reshmi Mukerji, MPH, and David E. Briles, PhD, of University of Alabama at Birmingham.
The new bacteria also seem to be causing meningitis infections in an unexpected way. Unlike the PCV strains, which tend to travel to the brain via the bloodstream, the new non-PCV bacteria don’t often cause blood infections, possibly because their capsules are not effective in resisting the blood’s immune system.
Instead, the study’s authors believe that the non-PCV bacteria build colonies in the nose, throat, or ears and then migrate directly to the brain from those locations.