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Bacterial Meningitis Causes Lifelong Effects in One-Third of Children

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Meningitis is an infection of the membranes (meninges) that surround the central nervous system. It is an illness feared by many parents due to its potential to cause severe disability and even death.

The different types of meningitis infections

Meningitis can be caused by several species of bacteria, fungi, viruses and parasites. While bacterial meningitis is rarer than viral meningitis, it is also more dangerous and can be fatal within 24 hours. Four species of bacteria contribute to over 50% of meningitis deaths globally: Neisseria meningitidis (N. meningitidis), Streptococcus pneumoniae (S. pneumoniae), Haemophilus influenzae (H. influenzae) and Streptococcus agalactiae (S. agalactiae).

Though bacterial meningitis can affect individuals of any age, it is more common in young children and adolescents. The standard-of-care treatment protocol for bacterial meningitis typically involves the administration of intravenous antibiotic therapy and, in some circumstances, corticosteroids.

In many cases, this protocol is effective and there are no long-term side effects from the infection. But for some patients, bacterial meningitis causes lifelong challenges, the burden of which is not yet fully understood. A new study by researchers at the Karolinska Institute, published in JAMA Network Open, sheds some light.

How bacterial meningitis infections affect the brain

“Bacterial meningitis is not only an infectious disease,” explained Dr. Federico Iovino, associate professor, principal investigator and group leader in the laboratory of neuro-infections and neuroinflammation at the Karolinska Institute in Sweden. “Even when the infection is fought successfully, the infection of the brain causes neuronal damage that leads to permanent neurological disabilities. Such disabilities tremendously affect life quality. It is therefore a critical socio-economic burden, not only in Sweden.”

Research exploring the long-term effects of childhood bacterial meningitis has focused on well-recognized disabilities such as hearing loss. Iovino’s laboratory wanted to investigate the risks of less visible disabilities, such as behavioral disorders or psychiatric diseases.

Iovino and colleagues created a study in Sweden that matched individuals diagnosed with childhood bacterial meningitis from January 1, 1987, to December 31, 2021, with members of the general public. In the primary analysis, they explored the risk of post-meningitis functional disabilities in six categories:

  • Cognitive disabilities
  • Seizures
  • Hearing loss
  • Motor function disorders
  • Visual disturbances
  • Behavioral and emotional disorders

They also examined the risk of a type of post-meningitis complication called intracranial structural injuries. The six functional disabilities and one complication analyzed are collectively referred to as “disabilities” in the paper.

The researchers then further stratified these risks by the three major causes of bacterial meningitis, S. pneumoniae, N. meningitidis and H. influenzae, and by age at diagnosis. In their secondary analyses, they investigated the number of disabilities across the matched groups.

In total, Iovino and colleagues compared 3,500 individuals that contracted childhood bacterial meningitis with 32,000 matched controls, over an average follow-up period of 23 years.

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One-third of childhood bacterial meningitis cases result in long-term disability

Individuals diagnosed with childhood bacterial meningitis had a higher incidence of all 7 disabilities analyzed, with 29% having at least 1 disability.

The highest risks were observed for hearing loss, behavioral and emotional disorders as well as visual disturbances.

Risks for cognitive disabilities, seizures, hearing loss and motor function disorders were significantly higher for S. pneumoniae infections compared to H. influenzae and N. meningitidis infections. Expanding on this finding, Iovino said: “One of our latest research studies shows that bacterial invasion affects all brain regions. Our sensory-motor functions are controlled by different parts of the brain; therefore, it was expected to observe such a variety of neurological sequelae considering that all brain regions are affected by bacterial invasion during meningitis pathogenesis.”

Meningitis outcomes – timing of treatment is key

Given that the diagnoses analyzed in the study were across a prolonged period of time (1987–2021), it’s possible that evolving criteria for the diagnosis and treatment of bacterial meningitis could have affected patient outcomes.

Technology Networks asked Iovino if the research uncovered any particular treatment plans that were associated with a higher or lower risk of long-term disability. “Absolutely,” he said. “Antibiotics can treat the infection; what is challenging is the timeline of treatment. Meningitis onset develops incredibly fast, if not promptly treated it can kill within 24–48 hours. Unfortunately, antibiotic treatment takes several days, because antibiotics have low capability to penetrate the blood-brain barrier, and also antibiotic-resistance is a constant threat in the clinics. Over these days, neurons are continuously damaged by the infection, and unlike many cells in our body, damaged neurons can be neither repaired nor replaced.”

Iovino emphasized that new therapeutic approaches are sorely needed to protect neurons from bacteria attacking the brain, which is a large focus of his current research at the Karolinska Institute.

Meningitis prevention

While the study focused on Swedish individuals, Iovino expects the results would be similar across other regions: “In low-income countries in which vaccination programs are not implemented (such as sub-Saharan Africa, the so called “meningitis belt”), the incidence of neurological sequelae post-meningitis is most likely even higher,” he said.

The study sheds light on the importance of vaccination programs to prevent meningitis infections. The Centers for Disease Control and Prevention provides comprehensive information on meningitis symptoms and available immunization strategies. 

Dr. Federico Iovino was speaking to Molly Campbell, Senior Science Writer for Technology Networks.

About the interviewee

Dr. Federico Iovino is an associate professor, principal investigator and group leader in his laboratory at the Karolinska Institute. His research investigates bacterial interactions within brain cells during bacterial meningoencephalitis pathogenesis. Iovino studied human biology and biomedical sciences at the University of Pavia in Italy, before completing a PhD in medical microbiology at the University Medical Center of Groningen. After graduating from his PhD, Iovino began a postdoctoral position in the department of microbiology, tumor and cell biology at the Karolinska Institute. In January 2021, he started his own independent laboratory of neuro-infections and neuroinflammation in the department of neuroscience at the Karolinska Institute.

Reference: Mohanty S, Johansson Kostenniemi U, Silfverdal SA, et al. Increased risk of long-term disabilities following childhood bacterial meningitis in Sweden. JAMA Netw Open. 2024;7(1):e2352402-e2352402. doi: 10.1001/jamanetworkopen.2023.52402