Epidemiologic trend of adult bacterial meningitis in southern Taiwan (2006–2015)

Global Case Fatality of Bacterial Meningitis During an 80-Year Period: A Systematic Review and Meta-Analysis

Importance

The impact of vaccination, antibiotics, and anti-inflammatory treatment on pathogen distribution and outcome of bacterial meningitis over the past century is uncertain.

Objective

To describe worldwide pathogen distribution and case fatality ratios of community-acquired bacterial meningitis.

Data Sources

Google Scholar and MEDLINE were searched in January 2022 using the search terms bacterial meningitis and mortality.

Study Selection

Included studies reported at least 10 patients with bacterial meningitis and survival status. Studies that selected participants by a specific risk factor, had a mean observation period before 1940, or had more than 10% of patients with health care-associated meningitis, tuberculous meningitis, or missing outcome were excluded.

Data Extraction and Synthesis

Data were extracted by 1 author and verified by a second author. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Random-effects models stratified by age (ie, neonates, children, adults), Human Development Index (ie, low-income or high-income countries), and decade and meta-regression using the study period's year as an estimator variable were used.

Main Outcome and Measure

Case fatality ratios of bacterial meningitis.

Results

This review included 371 studies performed in 108 countries from January 1, 1935, to December 31, 2019, describing 157 656 episodes. Of the 33 295 episodes for which the patients' sex was reported, 13 452 (40%) occurred in females. Causative pathogens were reported in 104 598 episodes with Neisseria meningitidis in 26 344 (25%) episodes, Streptococcus pneumoniae in 26 035 (25%) episodes, Haemophilus influenzae in 22 722 (22%), other bacteria in 19 161 (18%) episodes, and unidentified pathogen in 10 336 (10%) episodes. The overall case fatality ratio was 18% (95% CI, 16%-19%), decreasing from 32% (95% CI, 24%-40%) before 1961 to 15% (95% CI, 12%-19%) after 2010. It was highest in meningitis caused by Listeria monocytogenes at 27% (95% CI, 24%-31%) and pneumococci at 24% (95% CI, 22%-26%), compared with meningitis caused by meningococci at 9% (95% CI, 8%-10%) or H influenzae at 11% (95% CI, 10%-13%). Meta-regression showed decreasing case fatality ratios overall and stratified by S pneumoniae, Escherichia coli, or Streptococcus agalactiae (P < .001).

Conclusions and Relevance

In this meta-analysis with meta-regression, declining case fatality ratios of community-acquired bacterial meningitis throughout the last century were observed, but a high burden of disease remained.

The clinical characteristics and therapeutic outcomes of adult patients with community-acquired spontaneous bacterial meningitis with a fulminant clinical course in Taiwan

PURPOSE

To examine the clinical characteristics of adult patients with community-acquired spontaneous bacterial meningitis (CASBM) with a fulminant clinical course.

MATERIALS AND METHODS

The clinical features and therapeutic outcomes of 127 adult CASBM patients were analyzed. The patients were divided into two groups as those with and without a fulminant clinical course. Fulminant clinical course was defined as meningitis presenting initially with marked consciousness disturbance (Glasgow Coma Scale score < 8) or a rapid deterioration in consciousness level within 48 h of hospitalization.

RESULTS

Among the 127 enrolled patients, 69 had a fulminant clinical course (47 men and 22 women) and 58 did not. The patients with a fulminant clinical course had a significantly higher incidence of end-stage renal disease (ESRD), severe clinical manifestations and higher mortality rate, and the survivors had significantly worse therapeutic outcomes. Klebsiella (K.) pneumoniae (50 strains) was the most important pathogen for the development of a fulminant clinical course, and all strains were susceptible to ceftriaxone and ceftazidime. With treatment, 50.7% (35/69) of the patients with a fulminant clinical course died, and the presence of K. pneumoniae infection was significant prognostic factor.

CONCLUSIONS

The presence of ESRD, initial presentation of altered consciousness, septic shock, seizures and CSF total protein level and K. pneumoniae infection were significantly associated with a fulminant clinical course of adult CASBM, and patients with this specific infectious syndrome had high mortality and morbidity rates. The presence of K. pneumoniae infection is a significant prognostic factor.

Polymicrobial Bacterial Meningitis in a Patient with Chronic Suppurative Otitis Media: Case Report and Literature Review

Polymicrobial meningitis is a rare entity in the adult population, especially in the antibiotic era. However, disorders such as chronic suppurative otitis media (CSOM) or even poor oral hygiene are considered risk factors for the development of such cerebral infection. We report a case of polymicrobial meningitis associated with oto-mastoiditis in a 64-year-old female patient known to have CSOM. The patient presented atypical symptoms for community-acquired meningitis, showing subacute evolution of headache, without fever or neck stiffness. The aerobe microorganisms Streptococcus anginosus and Corynebacterium spp., sensitive to beta-lactamines, and the anaerobe Prevotella spp., resistant to penicillin and metronidazole, were isolated from CSF specimens, while Proteus mirabilis and Enterococcus faecalis were identified from the ear drainage. The diversity of pathogens identified in our case led us to the hypothesis of two different sources of meningitis: otogenic and/or odontogenic. Favorable evolution was obtained after a multi-disciplinary approach, combining surgery and broad-spectrum antibiotics. In addition, we performed a literature review that highlights the low incidence of polymicrobial mixed aerobe-anaerobe meningitis.

Hypervirulent carbapenem-resistant Klebsiella pneumoniae causing highly fatal meningitis in southeastern China

Klebsiella pneumoniae (K. pneumoniae) is one of the most common causes of bacterial meningitis worldwide. The purpose of this study was to investigate the clinical and microbiological characteristics of K. pneumoniae meningitis, as well as the association of antimicrobial resistance, virulence, and patient prognosis. The clinical data of patients with K. pneumoniae meningitis from 2014 to 2020 in a tertiary teaching hospital were retrospectively evaluated. Antimicrobial susceptibility profiles were performed by the agar dilution method and broth microdilution method. The isolates were detected for virulence-related genes, resistance genes, capsular serotypes, and molecular subtypes. A total of 36 individuals with K. pneumoniae meningitis were included in the study, accounting for 11.3% (36/318) of all cases of bacterial meningitis. Of the 36 available isolates, K1, K47, and K64 were tied for the most frequent serotype (7/36, 19.4%). MLST analysis classified the isolates into 14 distinct STs, with ST11 being the most common (14/36, 38.9%). Carbapenem resistance was found in 44.4% (16/36) of the isolates, while hypervirulent K. pneumoniae (HvKP) was found in 66.7% (24/36) of the isolates. The isolates of hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP) were then confirmed to be 36.1% (13/36). Importantly, individuals with meningitis caused by Hv-CRKP had a statistically significant higher mortality than the other patients (92.3%, 12/13 vs. 56.5%, 13/23; P < 0.05). The high percentage and fatality of K. pneumoniae-caused meningitis, particularly in Hv-CRKP strains, should be of significant concern. More effective surveillance and treatment solutions will be required in future to avoid the spread of these life-threatening infections over the world.

Use of the FilmArray® Meningitis/Encephalitis panel to detect pathogenic microorganisms in cerebrospinal fluid specimens: a single-center retrospective study

OBJECTIVE

Meningitis and encephalitis are neurological emergencies requiring rapid diagnosis and treatment. The performance of the FilmArray® Meningitis/Encephalitis (ME) panel, a multiplex polymerase chain reaction test, and conventional methods for diagnosing meningitis and encephalitis was compared.

METHODS

This retrospective study assessed 20 patients diagnosed with meningitis or encephalitis according to clinical symptoms and laboratory examination findings between January 2018 and December 2019. The results of the FilmArray® ME panel were compared with those of conventional methods.

RESULTS

Pathogens were identified in 11 (55%) patients using the FilmArray® ME panel and in nine (45%) patients using conventional methods. The test identified herpes simplex virus type 1 in two patients, herpes simplex virus type 2 in one, varicella-zoster virus in four, Streptococcus pneumoniae in three, and Cryptococcus neoformans in one. Furthermore, additional pathogens were detected (n = 1, S. pneumoniae and n = 1, varicella-zoster virus). The median times to pathogen identification were 2 hours using the FilmArray® ME panel and 96 hours with conventional methods.

CONCLUSIONS

The sensitivity of the FilmArray® ME panel for rapidly detecting the most common pathogens was similar to that of conventional methods. Hence, this method could decrease the time to definitive diagnosis and treatment initiation.

Case report: Meningitis and intracranial aneurysm caused by mixed infection of oral microflora dominated by anaerobes

Introduction

Meningitis caused by oral anaerobic bacteria is rare, especially when complicated with an infected intracranial aneurysm. This paper has described an extremely rare case of bacterial meningitis caused by a mixed infection of oral microflora dominated by anaerobes, which developed cerebral infarcts, brain abscess, intracranial aneurysm, and severe hydrocephalus during treatment.

Case report

We describe a 65-year-old male patient who was presented with fever and headache as the initial symptoms and then developed left ophthalmoplegia, right hemiplegia, and disturbance of consciousness. Brain imaging showed that intracranial lesions were increased progressively, and cerebral infarcts, brain abscesses, intracranial aneurysm, and severe hydrocephalus were appeared gradually. Eventually, we diagnosed it as anaerobic meningitis by making deoxyribonucleic acid sequencing from the brain abscess pus. After using an anti-microbial regimen that can sufficiently cover anaerobes, the patient's condition was effectively controlled.

Conclusion

Anaerobic meningitis can cause a series of intracranial complications. Among them, the intracranial aneurysm is extremely rare. When evidence shows that the infection originates from oral flora, physicians should consider the possibility of this type of encephalitis. An early diagnosis and timely treatment are crucial to improving the prognosis.

Convergence of carbapenem-resistance and hypervirulence leads to high mortality in patients with postoperative Klebsiella pneumoniae meningitis

OBJECTIVE

To investigate the characteristics of Klebsiella pneumoniae meningitis and impact of convergence of carbapenem-resistance and hypervirulence on mortality.

METHODS

Drug-resistance and virulence-related genes were investigated in 25 K. pneumoniae strains causing meningitis. The clinical data of 25 patients (February 2009 to February 2019) were evaluated. Multilocus sequence typing, serotyping, mobile genetic element, and pulsed-field gel electrophoresis analysis were applied to generate the data. GraphPad Prism 8 was used for statistical analysis.

RESULTS

A mortality rate of 30.0% was found in the patients with K. pneumoniae meningitis. Significant differences were observed between the non-survivor and survivor groups in terms of mechanical ventilation, peripheral deep vein catheter insertion, ICU stay, and GCS and not in sex, age, and meningeal integrity destruction. Multi-drug resistance was found in 21 strains. Different detection rates were observed for each virulence gene, ranging from 8.0% in wzy-K1 to 100.0% in entB. Detection rates of carbapenem-resistant K. pneumoniae (CRKP), hypervirulent K. pneumoniae (HvKP), and hypervirulent carbapenem-resistant K. pneumoniae (Hv-CRKP) were 68.0%, 68.0%, and 48.0%, respectively. Totally 16 clusters and 19 clones were identified among the 25 strains. Mortality rates were significantly different between the non-Hv-CRKP (1/11) and Hv-CRKP groups (5/9), but comparable among the carbapenem-susceptible K. pneumoniae (CSKP)/CRKP groups and classical K. pneumoniae (cKP)/HvKP groups.

CONCLUSIONS

K. pneumoniae meningitis is associated with high mortality. K. pneumoniae-induced meningitis has highly divergent origins. Convergence of carbapenem-resistance and hypervirulence leads to high mortality in patients with K. pneumoniae meningitis, which is of great clinical concern.

Spontaneous community-acquired bacterial meningitis in adults admitted to the intensive care units in the Caribbean French West Indies: Unusual prevalence of Klebsiella pneumonia

An unusual prevalence of Klebsiella pneumoniae (24%) was observed in 25 adults admitted to the intensive care units of two University Hospitals in the French West Indies, for spontaneous community-acquired bacterial meningitis. All tested isolates had several prominent features of hypervirulent isolates, including rmpa and iuc genes, K1 or K2 capsular serotypes.

Hyponatremia in Infectious Diseases-A Literature Review

Hyponatremia is one of the most common water-electrolyte imbalances in the human organism. A serum sodium concentration threshold of less than 135 mmol/L is diagnostic for hyponatremia. The disorder is usually secondary to various diseases, including infections. Our review aims to summarize the diagnostic value and impact of hyponatremia on the prognosis, length of the hospitalization, and mortality among patients with active infection. The scientific literature regarding hyponatremia was reviewed using PubMed, ClinicalKey, and Web of Science databases. Studies published between 2011 and 2020 were screened and eligible studies were selected according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement and specific inclusion criteria. The most common infections that were associated with hyponatremia were viral and bacterial infections, including COVID-19 (coronavirus disease 2019). The etiology varied according to the infection site, setting and patient cohort it concerned. In several studies, hyponatremia was associated with prolonged hospitalization, worse outcomes, and higher mortality rates. Hyponatremia can also play a diagnostic role in differentiating pathogens that cause a certain infection type, as it was observed in community-acquired pneumonia. Although many mechanisms leading to hyponatremia have already been described, it is impossible with any certainty to ascribe the etiology of hyponatremia to any of them.

Septic Meningitis and Liver Abscess due to Hypermucoviscous Klebsiella pneumoniae Complicated with Chronic Strongyloidiasis in a Human T-lymphotropic Virus 1 Carrier

Recently, severe cases of infection due to hypermucoviscous Klebsiella pneumonia (hmKP) have been reported in Japan. The Amami Islands in Japan are also endemic regions for Strongyloides stercoralis. Disseminated strongyloidiasis strain often causes severe enterobacteria infection; however, whether or not chronic strongyloidiasis induces it remains unclear. We herein report a 71-year-old man who developed meningitis and liver abscess due to hmKP complicated with chronic strongyloidiasis. He died on the seventh hospital day. Strongyloides stercoralis were only found around the polyp in the cecum. Chronic strongyloidiasis can also induce severe infection due to enterobacteria, especially hypervirulent pathogens like hmKP, through the induction of mucosal rupture.

High incidence of severe neurological manifestations and high mortality rate for adult Listeria monocytogenes meningitis in Taiwan

The clinical characteristics and therapeutic outcomes of adult Listeria monocytogenes meningitis are not commonly examined in isolation in the literature. During a study period of 19 years (2000-2018), 366 patients with culture-proven adult bacterial meningitis (ABM) were identified in the author's hospital (264 patients in 2000-2010 and 102 patients in 2011-2018). Of the 366 ABM patients, 330 had monomicrobial infections while the other 36 had mixed infections. L. monocytogenes infection was identified in 11 of the 330 patients with monomicrobial ABM (3 in 2000-2010 and 8 in 2011-2018). These 11 patients included 5 males and 6 females, aged 47 to 76 years (median age = 61.7). None of the 11 patients had a postneurosurgical state as the underlying cause, but 3 of them contracted the infection nosocomially. Common underlying conditions included liver cirrhosis (4), systemic malignancy (3), diabetes mellitus (3), and renal disease (2). The most common clinical manifestations were fever (11), altered consciousness (8), seizure (8), bacteremia (7) and hydrocephalus (5). The therapeutic result revealed a mortality rate of 72.7% (8/11), but no significant prognostic factors were identified. The clinical features of 8 additional Taiwanese L. monocytogenes ABM patients reported in the literature, were also included for analysis. The present study revealed an increase in L. monocytogenes ABM in recent years and most patients presented with severe neurological manifestations. The current study is a preliminary overview of L. monocytogenes meningitis in adults and a further large-scale study is needed for improved delineation of this specific infectious syndrome.

The clinical characteristics, implicated pathogens and therapeutic outcomes of culture-proven septic cavernous sinus thrombosis

In this magnetic resonance imaging-based study, we investigated the clinical features, neuroimaging features and therapeutic outcomes of 14 adults (eight men and six women; mean age 60.4 years; range 37-77 years) with septic cavernous sinus thrombosis (CST). Of the underlying conditions, 10 had diabetes mellitus and 13 had concomitant sphenoid sinusitis. Headache (n = 13) and ophthalmoplegia (n = 13) were the most common clinical presentations, followed by fever (n = 9) and other neuro-vascular signs and symptoms. The duration from the onset of symptoms to diagnosis ranged from 1 to 61 days, and more than 64% (9/14) of the septic CST patients were diagnosed >7 days after symptom onset. Expansion of the cavernous sinus was the most common neuroimaging feature, followed by convexity of the lateral wall of the cavernous sinus (5) and filling defect of the cavernous sinus (4). Staphylococcal species (spp.) was the most commonly implicated pathogen, followed by Aspergillus spp. Despite treatment, 7% (1/14) of the patients died in the hospital and 67% (8/12) of the survivors had neurological deficits. The duration of onset-to-diagnosis and the presence of hemiparesis were significant prognostic factors. These results provide a preliminary view of this uncommon infectious syndrome. Further large-scale studies are needed to better delineate septic CST in adults.

Usefulness of the FilmArray meningitis/encephalitis (M/E) panel for the diagnosis of infectious meningitis and encephalitis in Taiwan

BACKGROUND/PURPOSE

Early recognition of causative pathogens is critical for the appropriate management of central nervous system infection and improved outcomes. The BioFire^® FilmArray^® Meningitis/Encephalitis Panel (BioFire^® ME Panel, BioFire Diagnostics) is the first U.S. Food and Drug Administration (FDA)-approved multiplex PCR assay that allows the rapid detection of 14 pathogens, including bacteria (n = 6), viruses (n = 7), and fungi (n = 1), from cerebrospinal fluid (CSF). The performance of the panel is expected to be dependent on the epidemiology of M/E in different geographical regions.

METHODS

In this preliminary study, we used the BioFire^® ME Panel in 42 subjects who presented to the emergency department with symptoms of M/E in our hospital. The results were compared to conventional culture, antigen detection, PCR, and various laboratory findings.

RESULTS

The panel detected six positive samples, of which five were viral and one bacterial. We observed an overall agreement rate of 88% between the BioFire^® ME Panel results and the conventional methods. There were no false-positive findings, but five discordant results were observed for enterovirus, herpes simplex virus type 1, Escherichia coli, and Cryptococcus species.

CONCLUSIONS

The BioFire^® ME Panel performed equivalently to the traditional PCR methods for virus detection, and better than bacterial cultures. This revolutionary system represents a paradigm shift in the diagnosis of M/E and may aid in the rapid identification of community-acquired M/E. However, the usefulness of this tool is limited in regions with a high prevalence of infectious M/E caused by microorganisms not included in the panel.

The clinical characteristics of spontaneous Gram-negative bacterial meningitis in adults: A hospital-based study

The epidemiologic trend of acute bacterial meningitis can change more dramatically than any other bacterial disease, and a decrease in spontaneous adult bacterial meningitis (ABM) has been noted in serial studies of the epidemiologic trend of ABM in Taiwan. The purpose of this study was to analyze the clinical characteristics, laboratory data and therapeutic outcomes of 149 patients with spontaneous Gram-negative (G(-)) ABM collected during a study period of 31 years (1986-2016). The 149 patients included 107 men and 42 women, aged 18-86 years. The common underlying conditions were diabetes mellitus, liver cirrhosis and alcoholism, and the leading clinical presentations were fever, altered consciousness and septic shock. Compared the clinical characteristics of the patients identified in the study period of 2001-2106 to the patients identified in the study period of 1986-2000, the former group of patients had a significantly higher incidence of systemic malignance. In the recent 16 years (2001-2016), Klebsiella pneumoniae, Pseudomonas spp. and Escherichia coli were the leading three implicated bacterial pathogens of spontaneous G(-) ABM, accounting for 61.3% (38/62), 11.3% (7/62) and 11.3% (7/62%) of all cases, respectively. The overall mortality rate from spontaneous G(-) ABM was high (47.0%, 70/149) and the presence of septic shock and lower cerebrospinal fluid glucose level were significant prognostic factors. Because of the decreasing incidence of spontaneous ABM in Taiwan, close examination of this specific infectious syndrome is important in order to monitor the epidemiologic trend and improve the therapeutic strategy.

The clinical characteristics and therapeutic outcomes of cryptococcal meningitis in elderly patients: a hospital-based study

BACKGROUND

The elderly, and especially those with an immuno-compromised status, are vulnerable to infectious diseases. The purpose of this study was to examine the clinical characteristics and therapeutic outcomes of cryptococcal meningitis (CM) in elderly patients in Taiwan.

METHODS

Ninety-nine adult patients with CM were identified during a 15-year study period (2002-2016), of whom 38 elderly (≥ 65 years) patients (16 men and 22 women, median age 72.9 years; range 65-86 years) were included for analysis. The clinical characteristics and therapeutic outcomes of these patients were analyzed and compared to non-elderly adult patients (< 65 years) with CM.

RESULTS

Among the 38 patients, diabetes mellitus was the most common underlying condition (15), followed by adrenal insufficiency (7), malignancy (6), hematologic disorders (5), chronic obstructive pulmonary disease (5), autoimmune diseases (3), liver cirrhosis (3) and acquired immunodeficiency syndrome (1). Altered consciousness (29), fever (21) and headache (17) were the leading clinical manifestations. Positive cerebrospinal fluid and blood cultures for Cryptococcus (C.) neoformans were found in 26 and 9 patients, respectively. There were significant differences in gender, altered consciousness and recent cerebral infarction between the elderly and non-elderly groups. The elderly group had a high mortality rate (36.8%, 14/38), and the presence of cryptococcemia was the most significant prognostic factor.

CONCLUSIONS

This study offers a preliminary view of the clinical characteristics of CM in the elderly. The results suggest that elderly patients (≥ 65 years) are more vulnerable to CM than adults aged < 65 years. Compared to the non-elderly group, the elderly group had female predominance, higher rates of altered consciousness and recent cerebral infarction as the clinical presentation. The presence of cryptococcemia was a significant prognostic factor in the elderly group. This study is limited by the small number of patients, and further large-scale studies are needed to better delineate this specific infectious syndrome.

Endovascular Metal Devices for the Treatment of Cerebrovascular Diseases

Cerebrovascular disease involves various medical disorders that obstruct brain blood vessels or deteriorate cerebral circulation, resulting in ischemic or hemorrhagic stroke. Nowadays, platinum coils with or without biological modification have become routine embolization devices to reduce the risk of cerebral aneurysm bleeding. Additionally, many intracranial stents, flow diverters, and stent retrievers have been invented with uniquely designed structures. To accelerate the translation of these devices into clinical usage, an in-depth understanding of the mechanical and material performance of these metal-based devices is critical. However, considering the more distal location and tortuous anatomic characteristics of cerebral arteries, present devices still risk failing to arrive at target lesions. Consequently, more flexible endovascular devices and novel designs are under urgent demand to overcome the deficiencies of existing devices. Herein, the pros and cons of the current structural designs are discussed when these devices are applied to the treatment of diseases ranging broadly from hemorrhages to ischemic strokes, in order to encourage further development of such kind of devices and investigation of their use in the clinic. Moreover, novel biodegradable materials and drug elution techniques, and the design, safety, and efficacy of personalized devices for further clinical applications in cerebral vasculature are discussed.

Global etiology of bacterial meningitis: A systematic review and meta-analysis

Bacterial meningitis is a global public health concern, with several responsible etiologic agents that vary by age group and geographical area. The aim of this systematic review and meta-analysis was to assess the etiology of bacterial meningitis in different age groups across global regions. PubMed and EMBASE were systematically searched for English language studies on bacterial meningitis, limited to articles published in the last five years. The methodological quality of the studies was assessed using a customized scoring system. Meta-analyses were conducted to determine the frequency (percentages) of seven bacterial types known to cause meningitis: Escherichia coli, Haemophilus influenzae, Neisseria meningitidis, Streptococcus pneumoniae, group B Streptococcus agalactiae, Staphylococcus aureus, and Listeria monocytogenes, with results being stratified by six geographical regions as determined by the World Health Organization, and seven age groups. Of the 3227 studies retrieved, 56 were eligible for the final analysis. In all age groups, S. pneumoniae and N. meningitidis were the predominant pathogens in all regions, accounting for 25.1-41.2% and 9.1-36.2% of bacterial meningitis cases, respectively. S. pneumoniae infection was the most common cause of bacterial meningitis in the 'all children' group, ranging from 22.5% (Europe) to 41.1% (Africa), and in all adults ranging from 9.6% (Western Pacific) to 75.2% (Africa). E. coli and S. pneumoniae were the most common pathogens that caused bacterial meningitis in neonates in Africa (17.7% and 20.4%, respectively). N. meningitidis was the most common in children aged ±1-5 years in Europe (47.0%). Due to paucity of data, meta-analyses could not be performed in all age groups for all regions. A clear difference in the weighted frequency of bacterial meningitis cases caused by the different etiological agents was observed between age groups and between geographic regions. These findings may facilitate bacterial meningitis prevention and treatment strategies.