Leading Cause of Meningitis Shifts from S. Pneumoniae to K. Pneumoniae

Klebsiella pneumoniae (K. pneumoniae)overtook Streptococcus pneumoniae (S. pneumoniae) as the leading cause of adult community-acquired bacterial meningitis from 2009 to 2023 in Korea, according to a study published in the International Journal of Infectious Diseases.¹ With S. pneumoniae on the decline due to increased vaccination efforts, researchers believe increased awareness toward K. pneumoniae meningitisis warranted.

“In Korea, a national immunization program (NIP) against S. pneumoniae has been implemented for both children and older adults, yielding preventive benefits,” wrote authors of the study. “Nevertheless, the high rates of penicillin resistance and multidrug resistance in S. pneumoniae now pose a significant challenge to effective treatment. In addition, hypervirulent K. pneumoniae (HvKp) has emerged and spread as a major community pathogen.”

Despite the challenges in managing potential pneumococcal infections, vaccination has made instances of meningitis caused by S. pneumoniae significantly less prominent. According to the Meningitis Research Foundation, an estimated 1.6 million lives will be saved from vaccination by the year 2024.² However, despite the development of agents protecting against S. pneumoniae, this type of pneumococcal infection is still regarded as one of the leading causes of bacterial meningitis, along with Haemophilus influenzae, Neisseria meningitidis, and Listeria monocytogenes.^1,3

READ MORE: Pneumococcal Conjugate Vaccine Booster Maximizes Protection Against IPD

Amid these developments in protecting patients against bacterial meningitis and S. pneumoniae infection, there is currently no vaccine available to protect against K. pneumoniae, causing it to rise among patients in communities, like in Korea, where the current study was conducted. However, in places like the US, community-acquired K. pneumoniae meningitis is rare, causing researchers to investigate its prominence in a locale that has provided a lack of research on the occurrence.^1,4

“No recent multicenter study with a sufficiently large sample size was available to represent the current national situation,” they continued.¹ “We therefore undertook a nationwide, multicenter study covering 2009-2023 to describe current etiologic patterns of adult community-acquired bacterial meningitis in Korea and identify epidemiologic and clinical factors associated with patient outcomes.”

To better understand the trends in community-acquired bacterial meningitis caused by either K. pneumoniae or S. pneumoniae, researchers conducted a 15-year retrospective study across 17 hospitals in Korea. The study data spanned from January 2009 to May 2023, and it only included adults 18 or older that were admitted and had a discharge diagnosis of bacterial meningitis or identification of a bacterial pathogen from cerebrospinal fluid (CSF) or blood culture, or a positive multiplex polymerase chain reaction result from CSF.

As part of the study, patients’ outcomes were assessed at the final day of an antibiotic treatment plan. The clinical outcomes explored in the investigation were all-cause mortality; attributable mortality, otherwise known as death directly related to bacterial meningitis; and the development of neurologic sequelae. All neurologic sequelae included in the study were cerebral infarction, intracranial hemorrhage, hydrocephalus, brain abscess, and hearing disturbance.¹

The final analysis included a total of 248 adults (mean age, 61.1 years; 58.7% men) with community-acquired bacterial meningitis.

“This multicenter study provides updated epidemiologic data on community-acquired bacterial meningitis in Korea, highlighting a declining incidence of S. pneumoniae and a rising incidence of K. pneumoniae over the past 15 years,” they wrote.¹ “K. pneumoniae has increased substantially, rising from the third most common pathogen to the leading cause during the final third of the study period (2019-2023). This trend aligns with a recent single-center study from Korea published in 2021, which reported K. pneumoniae as the most frequently isolated pathogen (25.6%), followed by S. pneumoniae (18.6%).”

As previously mentioned, throughout the background ofinfections causing meningitis, as well as the vaccine developments in recent history, K. pneumoniaeis notably on the rise among adults in Korea when compared with instances of S. pneumoniae meningitis. Regarding the clinical outcomes explored among each type of infection, K. pneumoniae reported the highest all-cause mortality and attributable mortality.

With these findings and the ways in which they overlap with previous evidence, researchers suggested adjusting attention from S. pneumoniae meningitis to the growing prominence of K. pneumoniae meningitis. Amid this shift in prominence, they believe a shift in awareness is also warranted.

“This 15-year nationwide multicenter study of adult community-acquired bacterial meningitis in Korea, where pneumococcal vaccination is widespread among children and older adults and HvKp has emerged as an important community pathogen, reveals that the incidence of S. pneumoniae has declined, while K. pneumoniae has risen to become the predominant cause of meningitis,” concluded the authors of the study.¹ “Given its potential to cause poor clinical outcomes, K. pneumoniae meningitis warrants increased clinical awareness.”

READ MORE: Pneumococcal Resource Center

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REFERENCES

1. Kang MS, Lee SH, Jung SI, et al. Shift from Streptococcus pneumoniae to Klebsiella pneumoniae: a 15-year nationwide study of bacterial meningitis in Korea. IJID. Published online October 10, 2025:108114. https://doi.org/10.1016/j.ijid.2025.108114

2. Pneumococcal vaccines. Meningitis Research Foundation. April 7, 2025. Accessed October 13, 2025. https://www.meningitis.org/meningitis/vaccine-information/pneumococcal-vaccines

3. Meningitis. Mayo Clinic Staff. October 17, 2024. Accessed October 13, 2025. https://www.mayoclinic.org/diseases-conditions/meningitis/symptoms-causes/syc-20350508

4. Lee B, Yeroushalmi K, Me HM, Sojitra P, Jilani U, Iqbal S, Ahmed S, Verley J, Akella J. Community acquired Klebsiella pneumoniae meningitis: a case report. Germs. 2018 Jun 4;8(2):92-95. doi: 10.18683/germs.2018.1136.