Epidemiological and molecular characteristics of a highly lethal pneumococcal meningitis epidemic in Burkina Faso

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.

Serotype 1 pneumococcus: epidemiology, genomics, and disease mechanisms

Streptococcus pneumoniae (the 'pneumococcus') is a significant cause of morbidity and mortality worldwide, causing life-threatening diseases such as pneumonia, bacteraemia, and meningitis, with an annual death burden of over one million. Discovered over a century ago, pneumococcal serotype 1 (S1) is a significant cause of these life-threatening diseases. Our understanding of the epidemiology and biology of pneumococcal S1 has significantly improved over the past two decades, informing the development of preventative and surveillance strategies. However, many questions remain unanswered. Here, we review the current state of knowledge of pneumococcal S1, with a special emphasis on clinical epidemiology, genomics, and disease mechanisms.

Proteins of Streptococcus pneumoniae Involved in Iron Acquisition

Streptococcus pneumoniae is a human pathogen bacterium capable of using hemoglobin (Hb) and haem as a single iron source but not in presence of lactoferrin. This bacterium has developed a mechanism through the expression of several membrane proteins that bind to iron sources, between them a lipoprotein of 37 kDa called Spbhp-37 (Streptococcus pneumoniae haem-binding protein) involved in iron acquisition. The Spbhp-37 role is to maintain the viability of S. pneumoniae in presence of Hb or haem. This mechanism is relevant during the invasion of S. pneumoniae to human tissue for the acquisition of iron from hemoglobin or haem as an iron source.

Pneumococcal Meningitis Outbreaks in Africa, 2000-2018: Systematic Literature Review and Meningitis Surveillance Database Analyses

BACKGROUND

The meningitis belt of sub-Saharan Africa has traditionally experienced large outbreaks of meningitis mainly caused by Neisseria meningitidis. More recently, Streptococcus pneumoniae has been recognized as a cause of meningitis outbreaks in the region. Little is known about the natural history and epidemiology of these outbreaks, and, in contrast to meningococcal meningitis, there is no agreed definition for a pneumococcal meningitis epidemic. The aim of this analysis was to systematically review and understand pneumococcal meningitis outbreaks in Africa between 2000 and 2018.

METHODS

Meningitis outbreaks were identified using a systematic literature review and analyses of meningitis surveillance databases. Potential outbreaks were included in the final analysis if they reported at least 10 laboratory-confirmed meningitis cases above baseline per week with ≥50% of cases confirmed as pneumococcus.

RESULTS

A total of 10 potential pneumococcal meningitis outbreaks were identified in Africa between 2000 and 2018. Of these, 2 were classified as confirmed, 7 were classified as possible, and 1 was classified as unlikely. Three outbreaks spanned more than 1 year. In general, the outbreaks demonstrated lower peak attack rates than meningococcal meningitis outbreaks and had a predominance of serotype 1. Patients with pneumococcal meningitis tended to be older and had higher case fatality rates than meningococcal meningitis cases. An outbreak definition, which includes a weekly district-level incidence of at least 10 suspected cases per 100 000 population per week, with >10 cumulative confirmed cases of pneumococcus per year, would have identified all 10 potential outbreaks.

CONCLUSIONS

Given the frequency of and high case fatality from pneumococcal meningitis outbreaks, public health recommendations on vaccination strategies and the management of outbreaks are needed. Improved laboratory testing for S. pneumoniae is critical for early outbreak identification.

Utilization of Pneumococcal Vaccine and Penicillin Prophylaxis in Sickle Cell Disease in Three African Countries: Assessment among Healthcare Providers in SickleInAfrica

Sickle cell disease is a genetic disease with a predisposition to infections caused by encapsulated organisms, especially Streptococcus pneumoniae. Pneumococcal vaccines and prophylactic penicillin have reduced the rate of this infection and mortality in sickle cell disease. However, implementation of these interventions is limited in Africa. The objectives of the study were to assess health care providers' behaviors with the implementation of pneumococcal vaccination and penicillin prophylaxis and to identify barriers to their use. A 25-item online questionnaire was administered through SickleinAfrica: a network of researchers, and healthcare providers, in Ghana, Nigeria, and Tanzania, working to improve health outcomes of sickle cell disease in Africa. Data was collected and managed using the Research Electronic Data Capture (REDCap), tools and data analysis was done using STATA version 13 and R statistical software. Eighty-two medical practitioners responded to the questionnaire. Only 54.0 and 48.7% of respondents indicated the availability of published guidelines on sickle cell disease management and pneumococcal vaccine use, respectively, at their facilities. The majority (54.0%) perceived that the vaccines are effective but over 20.0% were uncertain of their usefulness. All respondents from Ghana and Tanzania affirmed the availability of guidelines for penicillin prophylaxis in contrast to 44.1% in Nigeria. Eighty-five percent of respondents affirmed the need for penicillin prophylaxis but 15.0% had a contrary opinion for reasons including the rarity of isolation of Streptococcus pneumoniae in African studies, and therefore, the uncertainty of its benefit. Lack of published guidelines on the management of sickle cell disease and doubts about the necessity of prophylactic measures are potential barriers to the implementation of effective interventions.

Changes in Invasive Pneumococcal Disease Caused by Streptococcus pneumoniae Serotype 1 Following Introduction of PCV10 and PCV13: Findings from the PSERENADE Project

Streptococcus pneumoniae serotype 1 (ST1) was an important cause of invasive pneumococcal disease (IPD) globally before the introduction of pneumococcal conjugate vaccines (PCVs) containing ST1 antigen. The Pneumococcal Serotype Replacement and Distribution Estimation (PSERENADE) project gathered ST1 IPD surveillance data from sites globally and aimed to estimate PCV10/13 impact on ST1 IPD incidence. We estimated ST1 IPD incidence rate ratios (IRRs) comparing the pre-PCV10/13 period to each post-PCV10/13 year by site using a Bayesian multi-level, mixed-effects Poisson regression and all-site IRRs using a linear mixed-effects regression (N = 45 sites). Following PCV10/13 introduction, the incidence rate (IR) of ST1 IPD declined among all ages. After six years of PCV10/13 use, the all-site IRR was 0.05 (95% credibility interval 0.04–0.06) for all ages, 0.05 (0.04–0.05) for <5 years of age, 0.08 (0.06–0.09) for 5–17 years, 0.06 (0.05–0.08) for 18–49 years, 0.06 (0.05–0.07) for 50–64 years, and 0.05 (0.04–0.06) for ≥65 years. PCV10/13 use in infant immunization programs was followed by a 95% reduction in ST1 IPD in all ages after approximately 6 years. Limited data availability from the highest ST1 disease burden countries using a 3 + 0 schedule constrains generalizability and data from these settings are needed.

Bacterial genome-wide association study of hyper-virulent pneumococcal serotype 1 identifies genetic variation associated with neurotropism

Hyper-virulent Streptococcus pneumoniae serotype 1 strains are endemic in Sub-Saharan Africa and frequently cause lethal meningitis outbreaks. It remains unknown whether genetic variation in serotype 1 strains modulates tropism into cerebrospinal fluid to cause central nervous system (CNS) infections, particularly meningitis. Here, we address this question through a large-scale linear mixed model genome-wide association study of 909 African pneumococcal serotype 1 isolates collected from CNS and non-CNS human samples. By controlling for host age, geography, and strain population structure, we identify genome-wide statistically significant genotype-phenotype associations in surface-exposed choline-binding (P = 5.00 × 10-08) and helicase proteins (P = 1.32 × 10-06) important for invasion, immune evasion and pneumococcal tropism to CNS. The small effect sizes and negligible heritability indicated that causation of CNS infection requires multiple genetic and other factors reflecting a complex and polygenic aetiology. Our findings suggest that certain pathogen genetic variation modulate pneumococcal survival and tropism to CNS tissue, and therefore, virulence for meningitis.

Declines in Pediatric Bacterial Meningitis in the Republic of Benin Following Introduction of Pneumococcal Conjugate Vaccine: Epidemiological and Etiological Findings, 2011-2016

BACKGROUND

Pediatric bacterial meningitis (PBM) remains an important cause of disease in children in Africa. We describe findings from sentinel site bacterial meningitis surveillance in children <5 years of age in the Republic of Benin, 2011-2016.

METHODS

Cerebrospinal fluid (CSF) was collected from children admitted to Parakou, Natitingou, and Tanguieta sentinel hospitals with suspected meningitis. Identification of Streptococcus pneumoniae (pneumococcus), Haemophilus influenzae, and Neisseria meningitidis (meningococcus) was performed by rapid diagnostic tests, microbiological culture, and/or polymerase chain reaction; where possible, serotyping/grouping was performed.

RESULTS

A total of 10 919 suspected cases of meningitis were admitted to the sentinel hospitals. Most patients were 0-11 months old (4863 [44.5%]) and there were 542 (5.0%) in-hospital deaths. Overall, 4168 CSF samples were screened for pathogens and a total of 194 (4.7%) PBM cases were confirmed, predominantly caused by pneumococcus (98 [50.5%]). Following pneumococcal conjugate vaccine (PCV) introduction in 2011, annual suspected meningitis cases and deaths (case fatality rate) progressively declined from 2534 to 1359 and from 164 (6.5%) to 14 (1.0%) in 2012 and 2016, respectively (P < .001). Additionally, there was a gradual decline in the proportion of meningitis cases caused by pneumococcus, from 77.3% (17/22) in 2011 to 32.4% (11/34) in 2016 (odds ratio, 7.11 [95% confidence interval, 2.08-24.30]). Haemophilus influenzae meningitis fluctuated over the surveillance period and was the predominant pathogen (16/34 [47.1%]) by 2016.

CONCLUSIONS

The observed decrease in pneumococcal meningitis after PCV introduction may be indicative of changing patterns of PBM etiology in Benin. Maintaining vigilant and effective surveillance is critical for understanding these changes and their wider public health implications.

Evaluation of pneumococcal meningitis clusters in Burkina Faso and implications for potential reactive vaccination

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From 2011 to 2017, Burkina Faso had 20 pneumococcal meningitis clusters of ≥ 5 cases per district/week.

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Clusters had a maximum weekly incidence of 7 cases and a maximum duration of 4 weeks.

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Most clusters occurred prior to 13-valent pneumococcal conjugate vaccine introduction.

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Clusters were caused by a mixture of serotypes, with serotype 1 being most common.

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Due to the limited cluster size and duration, there were no clear indications for reactive vaccination.

Background

To better understand how to prevent and respond to pneumococcal meningitis outbreaks in the meningitis belt, we retrospectively examined Burkina Faso’s case-based meningitis surveillance data for pneumococcal meningitis clusters and assessed potential usefulness of response strategies.

Methods

Demographic and clinical information, and cerebrospinal fluid laboratory results for meningitis cases were collected through nationwide surveillance. Pneumococcal cases were confirmed by culture, polymerase chain reaction (PCR), or latex agglutination; strains were serotyped using PCR. We reviewed data from 2011 to 2017 to identify and describe clusters of ≥ 5 confirmed pneumococcal meningitis cases per week in a single district. We assessed whether identified clusters met the 2016 WHO provisional pneumococcal meningitis outbreak definition: a district with a weekly incidence of >5 suspected meningitis cases/100,000 persons, >60% of confirmed meningitis cases caused by Streptococcus pneumoniae, and >10 confirmed pneumococcal meningitis cases.

Results

Twenty pneumococcal meningitis clusters were identified, with a maximum weekly incidence of 7 cases and a maximum duration of 4 weeks. Most identified clusters (15/20; 75%) occurred before nationwide introduction of 13-valent pneumococcal conjugate vaccine (PCV13) in October 2013. Most cases were due to serotype 1 (74%), 10% were due to PCV13 serotypes besides serotype 1, and 8 clusters had >1 serotype. While 6 identified clusters had a weekly incidence of >5 suspected cases/100,000 and all 20 clusters had >60% of confirmed meningitis cases due to S. pneumoniae, no cluster had >10 confirmed pneumococcal meningitis cases in a single week.

Conclusions

Following PCV13 introduction, pneumococcal meningitis clusters were rarely detected, and none met the WHO provisional pneumococcal outbreak definition. Due to the limited cluster size and duration, there were no clear instances where reactive vaccination could have been useful. More data are needed to inform potential response strategies.

Impact of 13-Valent Pneumococcal Conjugate Vaccine on Pneumococcal Meningitis, Burkina Faso, 2016-2017

BACKGROUND

In 2013, Burkina Faso introduced 13-valent pneumococcal conjugate vaccine (PCV13) into the routine childhood immunization program, to be administered to children at 8, 12, and 16 weeks of age. We evaluated the impact of PCV13 on pneumococcal meningitis.

METHODS

Using nationwide surveillance, we gathered demographic/clinical information and cerebrospinal fluid (CSF) results for meningitis cases. Pneumococcal cases were confirmed by culture, polymerase chain reaction (PCR), or latex agglutination; strains were serotyped using PCR. We compared annual incidence (cases per 100 000) 4 years after PCV13's introduction (2017) to average pre-PCV13 incidence (2011-2013). We adjusted incidence for age and proportion of cases with CSF tested at national laboratories.

RESULTS

In 2017, pneumococcal meningitis incidence was 2.7 overall and 10.5 (<1 year), 3.8 (1-4 years), 3.5 (5-14 years), and 1.4 (≥15 years) by age group. Compared to 2011-2013, PCV13-serotype incidence was significantly lower among all age groups, with the greatest decline among children aged <1 year (77%; 95% confidence interval [CI], 65%-84%). Among all ages, the drop in incidence was larger for PCV13 serotypes excluding serotype 1 (79%; 95% CI, 72%-84%) than for serotype 1 (52%; 95% CI, 44%-59%); incidence of non-PCV13 serotypes also declined (53%; 95% CI, 37%-65%). In 2017, 45% of serotyped cases among all ages were serotype 1 and 12% were other PCV13 serotypes.

CONCLUSIONS

In Burkina Faso, meningitis caused by PCV13 serotypes continues to decrease, especially among young children. However, the concurrent decline in non-PCV13 serotypes and short pre-PCV13 observation period complicate evaluation of PCV13's impact. Efforts to improve control of serotype 1, such as switching from a 3 + 0 schedule to a 2 + 1 schedule, may improve overall control of pneumococcal meningitis in this setting.

Construction of a pneumolysin deficient mutant in streptococcus pneumoniae serotype 1 strain 519/43 and phenotypic characterisation

Streptococcus pneumoniae capsular serotype 1 continues to pose a huge infectious disease burden in low- and middle-income countries, particularly in West Africa. However, studies on this important serotype have been hampered by the inability to genetically modify these strains. In this study we have genetically modified a serotype 1 strain (519/43), the first time that this has been achieved for this serotype, providing the methodology for a deeper understanding of its biology and pathogenicity. As proof of principle we constructed a defined pneumolysin mutant and showed that it lost its ability to lyse red blood cells. We also showed that when mice were infected intranasally with the mutant 519/43Δply there was no significant difference between the load of bacteria in lungs and blood when compared to the wild type 519/43. When mice were infected intraperitoneally there were significantly fewer bacteria recovered from blood for the mutant 519/43Δply strain, although all mice still displayed signs of disease. Our study demonstrates S. pneumoniae serotype 1 strains can be genetically manipulated using our methodology and demonstrate that the ability to cause pneumonia in mice is independent of active pneumolysin for the 519/43 serotype 1 strain.

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Mutagenesis in Serotype 1 S. pneumoniae is possible in strain 519/43.

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519/43 possess pneumolysin D380 N, however it is not more haemolytic than the pneumolysin present in D39.

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519/43 strain is capable of causing disease independently of pneumolysin.

Mortality from HIV-associated meningitis in sub-Saharan Africa: a systematic review and meta-analysis

INTRODUCTION

HIV-associated cryptococcal, TB and pneumococcal meningitis are the leading causes of adult meningitis in sub-Saharan Africa (SSA). We performed a systematic review and meta-analysis with the primary aim of estimating mortality from major causes of adult meningitis in routine care settings, and to contrast this with outcomes from clinical trial settings.

METHODS

We searched PubMed, EMBASE and the Cochrane Library for published clinical trials (defined as randomized-controlled trials (RCTs) or investigator-managed prospective cohorts) and observational studies that evaluated outcomes of adult meningitis in SSA from 1 January 1990 through 15 September 2019. We performed random effects modelling to estimate pooled mortality, both in clinical trial and routine care settings. Outcomes were stratified as short-term (in-hospital or two weeks), medium-term (up to 10 weeks) and long-term (up to six months).

RESULTS AND DISCUSSION

Seventy-nine studies met inclusion criteria. In routine care settings, pooled short-term mortality from cryptococcal meningitis was 44% (95% confidence interval (95% CI):39% to 49%, 40 studies), which did not differ between amphotericin (either alone or with fluconazole) and fluconazole-based induction regimens, and was twofold higher than pooled mortality in clinical trials using amphotericin based treatment (21% (95% CI:17% to 25%), 17 studies). Pooled short-term mortality of TB meningitis was 46% (95% CI: 33% to 59%, 11 studies, all routine care). For pneumococcal meningitis, pooled short-term mortality was 54% in routine care settings (95% CI:44% to 64%, nine studies), with similar mortality reported in two included randomized-controlled trials. Few studies evaluated long-term outcomes.

CONCLUSIONS

Mortality rates from HIV-associated meningitis in SSA are very high under routine care conditions. Better strategies are needed to reduce mortality from HIV-associated meningitis in the region.

Future Directions for Meningitis Surveillance and Vaccine Evaluation in the Meningitis Belt of Sub-Saharan Africa

In sub-Saharan Africa, bacterial meningitis remains a significant public health problem, especially in the countries of the meningitis belt, where Neisseria meningitidis serogroup A historically caused large-scale epidemics. In 2014, MenAfriNet was established as a consortium of partners supporting strategic implementation of case-based meningitis surveillance to monitor meningitis epidemiology and impact of meningococcal serogroup A conjugate vaccine (MACV). MenAfriNet improved data quality through use of standardized tools, procedures, and laboratory diagnostics. MenAfriNet surveillance and study data provided evidence of ongoing MACV impact, characterized the burden of non-serogroup A meningococcal disease (including the emergence of a new epidemic clone of serogroup C), and documented the impact of pneumococcal conjugate vaccine. New vaccines and schedules have been proposed for future implementation to address the remaining burden of meningitis. To support the goals of "Defeating Meningitis by 2030," MenAfriNet will continue to strengthen surveillance and support research and modeling to monitor the impact of these programs on meningitis burden in sub-Saharan Africa.

Bacterial Meningitis Epidemiology in Five Countries in the Meningitis Belt of Sub-Saharan Africa, 2015-2017

BACKGROUND

The MenAfriNet Consortium supports strategic implementation of case-based meningitis surveillance in key high-risk countries of the African meningitis belt: Burkina Faso, Chad, Mali, Niger, and Togo. We describe bacterial meningitis epidemiology in these 5 countries in 2015-2017.

METHODS

Case-based meningitis surveillance collects case-level demographic and clinical information and cerebrospinal fluid (CSF) laboratory results. Neisseria meningitidis, Streptococcus pneumoniae, or Haemophilus influenzae cases were confirmed and N. meningitidis/H. influenzae were serogrouped/serotyped by real-time polymerase chain reaction, culture, or latex agglutination. We calculated annual incidence in participating districts in each country in cases/100 000 population.

RESULTS

From 2015-2017, 18 262 suspected meningitis cases were reported; 92% had a CSF specimen available, of which 26% were confirmed as N. meningitidis (n = 2433; 56%), S. pneumoniae (n = 1758; 40%), or H. influenzae (n = 180; 4%). Average annual incidences for N. meningitidis, S. pneumoniae, and H. influenzae, respectively, were 7.5, 2.5, and 0.3. N. meningitidis incidence was 1.5 in Burkina Faso, 2.7 in Chad, 0.4 in Mali, 14.7 in Niger, and 12.5 in Togo. Several outbreaks occurred: NmC in Niger in 2015-2017, NmC in Mali in 2016, and NmW in Togo in 2016-2017. Of N. meningitidis cases, 53% were NmC, 30% NmW, and 13% NmX. Five NmA cases were reported (Burkina Faso, 2015). NmX increased from 0.6% of N. meningitidis cases in 2015 to 27% in 2017.

CONCLUSIONS

Although bacterial meningitis epidemiology varied widely by country, NmC and NmW caused several outbreaks, NmX increased although was not associated with outbreaks, and overall NmA incidence remained low. An effective low-cost multivalent meningococcal conjugate vaccine could help further control meningococcal meningitis in the region.

Reactive vaccination as a control strategy for pneumococcal meningitis outbreaks in the African meningitis belt: Analysis of outbreak data from Ghana

Streptococcus pneumoniae is increasingly recognised as an important cause of bacterial meningitis in the African meningitis belt. The World Health Organization sets guidelines for response to outbreaks of meningococcal meningitis, but there are no current guidelines for outbreaks where S. pneumoniae is implicated. We aimed to evaluate the impact of using a similar response to target outbreaks of vaccine-preventable pneumococcal meningitis in the meningitis belt. Here, we adapt a previous model of reactive vaccination for meningococcal outbreaks to estimate the potential impact of reactive vaccination in a recent pneumococcal meningitis outbreak in the Brong-Ahafo region of central Ghana using weekly line list data on all suspected cases over a period of five months. We determine the sensitivity and specificity of various epidemic thresholds and model the cases and deaths averted by reactive vaccination. An epidemic threshold of 10 suspected cases per 100,000 population per week performed the best, predicting large outbreaks with 100% sensitivity and more than 85% specificity. In this outbreak, reactive vaccination would have prevented a lower number of cases per individual vaccinated (approximately 15,300 doses per case averted) than previously estimated for meningococcal outbreaks. Since the burden of death and disability from pneumococcal meningitis is higher than that from meningococcal meningitis, there may still be merit in considering reactive vaccination for outbreaks of pneumococcal meningitis. More outbreak data are needed to refine our model estimates. Whatever policy is followed, we emphasize the importance of timely laboratory confirmation of suspected cases to enable appropriate decisions about outbreak response.

Environmental factors which can affect the burden of pneumococcal disease and the immune response to pneumococcal vaccines: the need for more precisely delineated vaccine recommendations

Introduction: Precision medicine describes the customization of healthcare tailored to the individual patient. Generally, vaccines are considered as public health tools rather than from the individual patient perspective. However, adult vaccination programs in particular should consider many different factors, at the individual level and also from societal, cultural and country-specific perspectives. Currently, most immunization programs, including those for pneumococcal vaccines, have only been adopted on the basis of age or medical risk. Areas covered: Based on a broad literature search, this review addresses possible environmental factors which can affect the burden of pneumococcal disease and the immune response to pneumococcal vaccines. Expert opinion: Factors which influence the incidence of pneumococcal disease and the reaction against pneumococcal vaccination, including personal conditions, geographic/ethnic factors and social risks, are diverse. To maximize the effects of pneumococcal vaccination, not only for public health but also to induce optimal effects at the individual level, vaccines need to be verified under diverse situations and with collaboration among relevant medical societies, governments, and the pharmaceutical industry. Whereas vaccines are generally considered only from the public health perspective, flexible, comprehensive and tailored pneumococcal immunization programs, with appropriate policy support, can generate a greater positive impact on public health.

Outbreak of Pneumococcal Meningitis, Paoua Subprefecture, Central African Republic, 2016-2017

We report a pneumococcal meningitis outbreak in the Central African Republic (251 suspected cases; 60 confirmed by latex agglutination test) in 2016–2017. Case-fatality rates (10% for confirmed case-patients) were low. In areas where a recent pneumococcal conjugate vaccine campaign was conducted, a smaller proportion of cases was seen in youngest children.

Seasonal upsurge of pneumococcal meningitis in the Central African Republic

A high incidence of bacterial meningitis was observed in the Central African Republic (CAR) from December 2015 to May 2017 in three hospitals in the northwest of the country that are within the African meningitis belt. The majority of cases were caused by Streptococcus pneumoniae (249/328; 75.9%), which occurred disproportionately during the dry season (November-April) with a high case-fatality ratio of 41.6% (95% confidence interval [CI] 33.0, 50.8%). High rates of bacterial meningitis during the dry season in the meningitis belt have typically been caused by Neisseria meningitidis (meningococcal meningitis), and our observations suggest that the risk of contracting S. pneumoniae (pneumococcal) meningitis is increased by the same environmental factors. Cases of meningococcal meningitis (67/328; 20.4%) observed over the same period were predominantly group W and had a lower case fatality rate of 9.6% (95% CI 3.6, 21.8%). Due to conflict and difficulties in accessing medical facilities, it is likely that the reported cases represented only a small proportion of the overall burden. Nationwide vaccination campaigns in the CAR against meningitis have been limited to the use of MenAfriVac, which targets only meningococcal meningitis group A. We therefore highlight the need for expanded vaccine coverage to prevent additional causes of seasonal outbreaks.

Seasonal upsurge of pneumococcal meningitis in the Central African Republic

A high incidence of bacterial meningitis was observed in the Central African Republic (CAR) from December 2015 to May 2017 in three hospitals in the northwest of the country that are within the African meningitis belt. The majority of cases were caused by Streptococcus pneumoniae (249/328; 75.9%), which occurred disproportionately during the dry season (November-April) with a high case-fatality ratio of 41.6% (95% confidence interval [CI] 33.0, 50.8%). High rates of bacterial meningitis during the dry season in the meningitis belt have typically been caused by Neisseria meningitidis (meningococcal meningitis), and our observations suggest that the risk of contracting S. pneumoniae (pneumococcal) meningitis is increased by the same environmental factors. Cases of meningococcal meningitis (67/328; 20.4%) observed over the same period were predominantly group W and had a lower case fatality rate of 9.6% (95% CI 3.6, 21.8%). Due to conflict and difficulties in accessing medical facilities, it is likely that the reported cases represented only a small proportion of the overall burden. Nationwide vaccination campaigns in the CAR against meningitis have been limited to the use of MenAfriVac, which targets only meningococcal meningitis group A. We therefore highlight the need for expanded vaccine coverage to prevent additional causes of seasonal outbreaks.

Diagnosis of bacterial meningitis in Ghana: Polymerase chain reaction versus latex agglutination methods

Bacterial meningitis is a public health crisis in the northern part of Ghana, where it contributes to very high mortality and morbidity rates. Early detection of the causative organism will lead to better management and effective treatment. Our aim was to evaluate the diagnostic accuracy of Pastorex and Wellcogen latex agglutination tests for the detection of bacterial meningitis in a resource-limited setting. CSF samples from 330 suspected meningitis patients within the northern zone of Ghana were analysed for bacterial agents at the zonal Public Health Reference Laboratory in Tamale using polymerase chain reaction (PCR) and two latex agglutination test kits; Pastorex and Wellcogen. The overall positivity rate of samples tested for bacterial meningitis was 46.4%. Streptococcus pneumoniae was the most common cause of bacterial meningitis within the sub-region, with positivity rate of 25.2%, 28.2% and 28.8% when diagnosed using Wellcogen, Pastorex and PCR respectively. The Pastorex method was 97.4% sensitive while the Wellcogen technique was 87.6% sensitive. Both techniques however produced the same specificity of 99.4%. Our study revealed that the Pastorex method has a better diagnostic value for bacterial meningitis than the Wellcogen method and should be the method of choice in the absence of PCR.

Streptococcus mitis Expressing Pneumococcal Serotype 1 Capsule

Streptococcus pneumoniae's polysaccharide capsule is an important virulence factor; vaccine-induced immunity to specific capsular polysaccharide effectively prevents disease. Serotype 1 S. pneumoniae is rarely found in healthy persons, but is highly invasive and a common cause of meningitis outbreaks and invasive disease outside of the United States. Here we show that genes for polysaccharide capsule similar to those expressed by pneumococci were commonly detected by polymerase chain reaction among upper respiratory tract samples from older US adults not carrying pneumococci. Serotype 1-specific genes were predominantly detected. In five oropharyngeal samples tested, serotype 1 gene belonging to S. mitis expressed capsules immunologically indistinct from pneumococcal capsules. Whole genome sequencing revealed three distinct S. mitis clones, each representing a cps1 operon highly similar to the pneumococcal cps1 reference operon. These findings raise important questions about the contribution of commensal streptococci to natural immunity against pneumococci, a leading cause of mortality worldwide.

Combined testing for herpes simplex virus and Mycobacterium tuberculosis DNA in cerebrospinal fluid of patients with aseptic meningitis in Burkina Faso, West Africa

BACKGROUND

Little is known about the involvement of herpes simplex virus (HSV) or Mycobacterium tuberculosis (MTB) as potentially curable causes of central nervous system (CNS) infections in sub-Saharan Africa.

OBJECTIVE

In this study, we developed a PCR assay dedicated to simultaneous testing of HSV1/HSV2 and MTB in Burkina Faso, a country where HSV is neglected as a cause of CNS infection and where TB prevalence is high.

METHODS

A consensus HSV1/HSV2 set of primers and probe were designed and combined to primers and probe targeting the IS6110 repetitive insertion sequence of MTB. Analytical performances of the assay were evaluated on reference materials. Cerebrospinal fluid (CSF) collected from subjects with aseptic meningitis was tested for HSV1/HSV2 and MTB DNA.

RESULTS

The UL29 gene was chosen as a highly conserved region targeted by the HSV1/HSV2 nucleic acid test. The lower limits of detection were estimated to be 2.45 copies/µL for HSV1, 1.72 copies/µL for HSV2, and 2.54 IS6110 copies per µL for MTB. The PCR was used in 202 CSF collected from subjects suspected of aseptic meningitis. Five samples (2.46%) tested positive, including two children positive for HSV1 (0.99%) and three adults tested positive for MTB (1.47%).

CONCLUSION

Using an in-house real-time PCR assay, we showed that both HSV and MTB are etiologic pathogens contributing to aseptic meningitis in Burkina Faso. This molecular test may have clinical utility for early diagnosis for those treatable CNS infections.

Meningococcus serogroup C clonal complex ST-10217 outbreak in Zamfara State, Northern Nigeria

After the successful roll out of MenAfriVac, Nigeria has experienced sequential meningitis outbreaks attributed to meningococcus serogroup C (NmC). Zamfara State in North-western Nigeria recently was at the epicentre of the largest NmC outbreak in the 21^st Century with 7,140 suspected meningitis cases and 553 deaths reported between December 2016 and May 2017. The overall attack rate was 155 per 100,000 population and children 5–14 years accounted for 47% (3,369/7,140) of suspected cases. The case fatality rate (CFR) among children 5–9 years was 10%, double that reported among adults ≥ 30 years (5%). NmC and pneumococcus accounted for 94% (172/184) and 5% (9/184) of the laboratory-confirmed cases, respectively. The sequenced NmC belonged to the ST-10217 clonal complex (CC). All serotyped pneumococci were PCV10 serotypes. The emergence of NmC ST-10217 CC outbreaks threatens the public health gains made by MenAfriVac, which calls for an urgent strategic action against meningitis outbreaks.

Continued occurrence of serotype 1 pneumococcal meningitis in two regions located in the meningitis belt in Ghana five years after introduction of 13-valent pneumococcal conjugate vaccine

Background

Increases in pneumococcal meningitis were reported from Ghanaian regions that lie in the meningitis belt in 2016–2017, despite introduction of 13-valent pneumococcal conjugate vaccine (PCV13) in 2012 using a 3-dose schedule (6, 10, and 14 weeks). We describe pneumococcal meningitis epidemiology in the Ghanaian Northern and Upper West regions across two meningitis seasons.

Methods

Suspected meningitis cases were identified using World Health Organization standard definitions. Pneumococcal meningitis was confirmed if pneumococcus was the sole pathogen detected by polymerase chain reaction, culture, or latex agglutination in cerebrospinal fluid collected from a person with suspected meningitis during December 2015-March 2017. Pneumococcal serotyping was done using PCR. Annual age-specific pneumococcal meningitis incidence (cases per 100,000 population) was calculated, adjusting for suspected meningitis cases lacking confirmatory testing.

Findings

Among 153 pneumococcal meningitis cases, 137 (89.5%) were serotyped; 100 (73.0%) were PCV13-type, including 85 (62.0%) that were serotype 1, a PCV13-targeted serotype. Persons aged ≥5 years accounted for 96.7% (148/153) of cases. Comparing 2015–2016 and 2016–2017 seasons, the proportion of non-serotype 1 PCV13-type cases decreased from 20.0% (9/45) to 4.1% (3/74) (p = 0.008), whereas the proportion that was serotype 1 was stable (71.1% (32/45) vs. 58.1% (43/74); p = 0.16). Estimated adjusted pneumococcal meningitis incidence was 1.8 in children aged <5 years and ranged from 6.8–10.5 in older children and adults.

Conclusions

High pneumococcal meningitis incidence with a large proportion of serotype 1 disease in older children and adults suggests infant PCV13 vaccination has not induced herd protection with this schedule in this high-transmission setting.

Genetic Determinants of Tetracycline Resistance in Clinical Streptococcus pneumoniae Serotype 1 Isolates from Niger

Streptococcus pneumoniae serotype 1 is the first cause of pneumococcal meningitis Niger. To determine the underlying mechanism of resistance to tetracycline in serotype 1 Streptococcus pneumoniae, a collection of 37 isolates recovered from meningitis patients over the period of 2002 to 2009 in Niger were analyzed for drug susceptibility, and whole genome sequencing (WGS) was performed for molecular analyses. MIC level was determined for 31/37 (83.8%) isolates and allowed detection of full resistance (MIC = 8 µg) in 24/31 (77.4%) isolates. No resistance was found to macrolides and quinolones. Sequence-types deduced from WGS were ST217 (54.1%), ST303 (35.1%), ST2206 (5.4%), ST2839 (2.7%) and one undetermined ST (2.7%). All tetracycline resistant isolates carried a Tn5253 like element, which was found to be an association of two smaller transposons of Tn916 and Tn5252 families. No tet(O) and tet(Q) genes were detected. However, a tet(M) like sequence was identified in all Tn5253 positive strains and was found associated to Tn916 composite. Only one isolate was phenotypically resistant to chloramphenicol, wherein a chloramphenicol acetyl transferase (cat) gene sequence homologous to cat_pC194 from the Staphylococcus aureus plasmid pC194 was detected. In conclusion, clinical Streptococcus pneumoniae type 1 isolated during 2002 to 2009 meningitis surveillance in Niger were fully susceptible to macrolides and quinolones but highly resistant to tetracycline (77.4%) through acquisition of a defective Tn5253 like element composed of Tn5252 and Tn916 transposons. Of the 31 tested isolates, only one was exceptionally resistant to chloramphenicol and carried a Tn5253 transposon that contained cat gene sequence.

Early impact of 13-valent pneumococcal conjugate vaccine on pneumococcal meningitis-Burkina Faso, 2014-2015

OBJECTIVES

We evaluate early impact of 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal meningitis in Burkina Faso.

METHODS

Nationwide surveillance gathered demographic/clinical information and cerebrospinal fluid (CSF) results for meningitis cases. Pneumococcal cases were confirmed by culture, polymerase chain reaction (PCR), or latex agglutination, and strains serotyped using PCR. We compared incidence (cases per 100,000) in the early post-PCV13 period (2014 and 2015) to average pre-PCV13 incidence (2011-2013).

RESULTS

In 2015, age-specific pneumococcal meningitis incidences were 8.7 (<1 year), 2.4 (1-4 years), 6.5 (5-14 years), and 2.6 (≥15 years). Compared to 2011-2013, PCV13-serotype incidence among all ages decreased by 32% (95%CI: 23%-39%), with significant decreases among children aged <1 year (76%; 95%CI: 64%-84%) and 1-4 years (58%, 95%CI: 40%-71%). Among all ages, incidence of PCV13 serotypes besides serotype 1 decreased (68%; 95%CI: 59%-75%), but serotype 1 incidence did not. Incidence of non-PCV13 serotypes also decreased (47%; 95%CI: 29%-60%). Among children aged <1 year, serotypes 12F/12A/12B/44/46 (17%), 1 (12%), and 5 (10%) predominated.

CONCLUSIONS

Following PCV13 introduction, PCV13-serotype meningitis incidence in young children significantly decreased. PCV13 impact on serotype 1 and disease in older children and adults requires continued monitoring.

Comparative Genomic Analysis and In Vivo Modeling of Streptococcus pneumoniae ST3081 and ST618 Isolates Reveal Key Genetic and Phenotypic Differences Contributing to Clonal Replacement of Serotype 1 in The Gambia

Streptococcus pneumoniae serotype 1 is one of the leading causes of invasive pneumococcal disease (IPD) in West Africa, with ST618 being the dominant cause of IPD in The Gambia. Recently however, a rare example of clonal replacement was observed, where the ST3081 clone of serotype 1 replaced the predominant ST618 clone as the main cause of IPD. In the current study, we sought to find the reasons for this unusual replacement event. Using whole-genome sequence analysis and clinically relevant models of in vivo infection, we identified distinct genetic and phenotypic characteristics of the emerging ST3081 clone. We show that ST3081 is significantly more virulent than ST618 in models of invasive pneumonia, and is carried at higher densities than ST618 during nasopharyngeal carriage. We also observe sequence type-specific accessory genes and a unique sequence type-specific fixed mutation in the pneumococcal toxin pneumolysin, which is associated with increased hemolytic activity in ST3081 and may contribute to increased virulence in this clone. Our study provides evidence that, within the same serotype 1 clonal complex, biological properties differ significantly from one clone to another in terms of virulence and host invasiveness, and that these differences may be the result of key genetic differences within the genome.

Four years of case-based surveillance of meningitis following the introduction of MenAfriVac in Moissala, Chad: lessons learned

OBJECTIVE

Case-based surveillance of bacterial meningitis in sentinel districts has been recommended after the introduction of the conjugated vaccine against Neisseria meningitidis serogroup A (NmA), MenAfriVac, in the African meningitis belt. Here we report data and lessons learnt from four years of surveillance in the district of Moissala, Chad.

METHODS

All suspected cases of meningitis were referred free of charge to the district hospital for lumbar puncture and treatment. Cerebrospinal fluid samples were tested with Pastorex latex agglutination in Moissala, and inoculated trans-isolate media were used for culture and PCR at the national reference laboratory and/or at the Norwegian Institute of Public Health.

RESULTS

From July 2012 to December 2016, 237 suspected cases of meningitis were notified, and a specimen was collected from 224. Eighty-three samples were positive for a bacterial pathogen by culture, PCR or Pastorex, including 58 cases due to Streptococcus pneumoniae with only 28 of 49 pneumococcal meningitis confirmed by culture or PCR correctly identified by Pastorex. Four cases of NmA were detected by Pastorex, but none were confirmed by PCR.

CONCLUSION

Implementation of case-based surveillance for meningitis is feasible in Chad, but has required political and technical engagement. Given the high proportion of S. pneumoniae and its poor detection by Pastorex, continued use of PCR is warranted for surveillance outside of outbreaks, and efforts to accelerate the introduction of pneumococcal conjugate vaccines are needed. Introduction of MenAfriVac in routine immunisation and future availability of a pentavalent meningococcal conjugate vaccine will be key elements for the sustained reduction in meningitis outbreaks in the area.

Immunogenicity and safety of 13-valent pneumococcal conjugate vaccine (PCV13) formulated with 2-phenoxyethanol in multidose vials given with routine vaccination in healthy infants: An open-label randomized controlled trial

BACKGROUND

This open-label randomized controlled trial in infants compared safety, tolerability, and immunogenicity of the 13-valent pneumococcal conjugate vaccine (PCV13) formulated with the preservative 2-phenoxyethanol (2-PE) in a multidose vial (MDV) to the current PCV13 without 2-PE in a single-dose syringe (SDS).

METHODS

Gambian infants were randomized 1:1 to receive PCV13 as either MDV or SDS at ages 2, 3, and 4months. Serotype-specific antipneumococcal antibody responses and opsonophagocytic activity ([OPA]; subset) were measured at age 5months. Noninferiority was declared if the lower bound of the 97.5% CI for the difference (MDV-SDS) in proportions of subjects achieving IgG concentrations ≥0.35μg/mL (primary endpoint) was greater than -10%. IgG geometric mean concentrations (GMCs) were noninferior if the lower limit of the two-sided 97.5% CI of the geometric mean ratio (MDV vs SDS) was greater than 0.5. Reactogenicity and other adverse events were collected.

RESULTS

500 participants were randomized and vaccinated; 489 (MDV: n=245; SDS: n=244) completed the trial. Noninferiority of MDV was demonstrated for all serotypes as measured by percentage of subjects achieving antibody responses above ≥0.35μg/mL. IgG GMCs (coprimary endpoint) also demonstrated noninferiority of MDV; OPA results supported these findings. Safety and tolerability were comparable between groups.

CONCLUSIONS

PCV13 in MDV was safe and immunogenic when administered according to the routine schedule to infants. MDV was noninferior to SDS for all 13 pneumococcal serotypes. Comparable immunogenicity and safety profiles of PCV13 MDV and SDS suggest PCV13 MDV can help optimize vaccination in resource-limited settings. ClinicalTrials.gov NCT01964716 https://clinicaltrials.gov/ct2/show/NCT01964716.

The global distribution and diversity of protein vaccine candidate antigens in the highly virulent Streptococcus pnuemoniae serotype 1

Serotype 1 is one of the most common causes of pneumococcal disease worldwide. Pneumococcal protein vaccines are currently being developed as an alternate intervention strategy to pneumococcal conjugate vaccines. Pre-requisites for an efficacious pneumococcal protein vaccine are universal presence and minimal variation of the target antigen in the pneumococcal population, and the capability to induce a robust human immune response. We used in silico analysis to assess the prevalence of seven protein vaccine candidates (CbpA, PcpA, PhtD, PspA, SP0148, SP1912, SP2108) among 445 serotype 1 pneumococci from 26 different countries, across four continents. CbpA (76%), PspA (68%), PhtD (28%), PcpA (11%) were not universally encoded in the study population, and would not provide full coverage against serotype 1. PcpA was widely present in the European (82%), but not in the African (2%) population. A multi-valent vaccine incorporating CbpA, PcpA, PhtD and PspA was predicted to provide coverage against 86% of the global population. SP0148, SP1912 and SP2108 were universally encoded and we further assessed their predicted amino acid, antigenic and structural variation. Multiple allelic variants of these proteins were identified, different allelic variants dominated in different continents; the observed variation was predicted to impact the antigenicity and structure of two SP0148 variants, one SP1912 variant and four SP2108 variants, however these variants were each only present in a small fraction of the global population (<2%). The vast majority of the observed variation was predicted to have no impact on the efficaciousness of a protein vaccine incorporating a single variant of SP0148, SP1912 and/or SP2108 from S. pneumoniae TIGR4. Our findings emphasise the importance of taking geographic differences into account when designing global vaccine interventions and support the continued development of SP0148, SP1912 and SP2108 as protein vaccine candidates against this important pneumococcal serotype.

Burden of Pneumococcal Disease in Northern Togo before the Introduction of Pneumococcal Conjugate Vaccine

Background

S. pneumoniae is a leading cause of meningitis morbidity and mortality in the African meningitis belt, but little is known of its contribution to the burden of pneumonia in the region. We aimed to estimate the incidence of pneumococcal disease in children and adults in northern Togo, before the introduction of pneumococcal conjugate vaccine (PCV).

Methods and findings

From May 1st 2010 to April 30th 2013, we systematically enrolled all hospitalized patients meeting a case definition of suspected meningitis or clinical pneumonia, residing in Tone or Cinkasse districts, northern Togo and providing informed consent. We collected clinical data and tested biological specimens according to standardized procedures, including bacteriology and PCR testing of cerebro-spinal fluid for meningitis patients and blood cultures and whole blood lytA PCR for pneumonia patients. Chest X-rays (CXR) were interpreted using the WHO methodology. We included 404 patients with meningitis (104 <5 years of age) and 1550 with pneumonia (251 <5 years) over the study period. Of these, 78 (19%) had pneumococcal meningitis (13 <5 years), 574 (37%) had radiologically-confirmed pneumonia (83 <5 years) and 73 (5%) had culture-confirmed pneumococcal pneumonia (2 <5 years). PCV13 serotypes caused 79% (54/68) of laboratory-confirmed pneumococcal meningitis and 83% (29/35) of culture-confirmed pneumococcal pneumonia. Serotype 1 predominated in meningitis (n = 33) but not in pneumonia patients (n = 1). The incidence of pneumococcal disease was 7.5 per 100,000 among children <5 years of age and 14.8 in persons 5 years of age and above in the study area. When considering CXR-confirmed and blood PCR-positive pneumonia cases as likely pneumococcal, incidence estimates increased to 43.7 and 66.0 per 100,000 in each of these age groups, respectively. Incidence was at least 3-fold higher when we restricted the analysis to the urban area immediately around the study hospitals.

Conclusions

Our findings highlight the important role of S. pneumoniae as a meningitis and pneumonia-causing pathogen in the African meningitis belt. Pneumococcal disease incidence in our population was substantially lower than expected from global models; we hypothesize that poor access to hospital care led us to substantially underestimate the burden of disease. Surveillance is ongoing and will enable an evaluation of PCV impact, providing novel, high quality data from the region.

Nationwide Trends in Bacterial Meningitis before the Introduction of 13-Valent Pneumococcal Conjugate Vaccine-Burkina Faso, 2011-2013

BACKGROUND

Following introduction of Haemophilus influenzae type b vaccine in 2006 and serogroup A meningococcal conjugate vaccine in 2010, Streptococcus pneumoniae (Sp) became the leading cause of bacterial meningitis in Burkina Faso. We describe bacterial meningitis epidemiology, focusing on pneumococcal meningitis, before 13-valent pneumococcal conjugate vaccine (PCV13) introduction in the pediatric routine immunization program in October 2013.

METHODS

Nationwide population-based meningitis surveillance collects case-level demographic and clinical information and cerebrospinal fluid (CSF) laboratory results. Sp infections are confirmed by culture, real-time polymerase chain reaction (rt-PCR), or latex agglutination, and CSF serotyped using real-time and conventional PCR. We calculated incidence rates in cases per 100,000 persons, adjusting for age and proportion of cases with CSF tested at national reference laboratories, and case fatality ratios (CFR).

RESULTS

During 2011-2013, 1,528 pneumococcal meningitis cases were reported. Average annual adjusted incidence rates were 26.9 (<1 year), 5.4 (1-4 years), 7.2 (5-14 years), and 3.0 (≥15 years). Overall CFR was 23% and highest among children aged <1 year (32%) and adults ≥30 years (30%). Of 1,528 cases, 1,036 (68%) were serotyped: 71% were PCV13-associated serotypes, 14% were non-PCV13-associated serotypes, and 15% were non-typeable by PCR. Serotypes 1 (45%) and 12F/12A/12B/44/46 (8%) were most common. Among children aged <1 year, serotypes 5 (15%), 6A/6B (13%) and 1 (12%) predominated.

CONCLUSIONS

In Burkina Faso, the highest morbidity and mortality due to pneumococcal meningitis occurred among children aged <1 year. The majority of cases were due to PCV13-associated serotypes; introduction of PCV13 should substantially decrease this burden.

Understanding pneumococcal serotype 1 biology through population genomic analysis

BACKGROUND

Pneumococcus kills over one million children annually and over 90 % of these deaths occur in low-income countries especially in Sub-Saharan Africa (SSA) where HIV exacerbates the disease burden. In SSA, serotype 1 pneumococci particularly the endemic ST217 clone, causes majority of the pneumococcal disease burden. To understand the evolution of the virulent ST217 clone, we analysed ST217 whole genomes from isolates sampled from African and Asian countries.

METHODS

We analysed 226 whole genome sequences from the ST217 lineage sampled from 9 African and 4 Asian countries. We constructed a whole genome alignment and used it for phylogenetic and coalescent analyses. We also screened the genomes to determine presence of antibiotic resistance conferring genes.

RESULTS

Population structure analysis grouped the ST217 isolates into five sequence clusters (SCs), which were highly associated with different geographical regions and showed limited intracontinental and intercontinental spread. The SCs showed lower than expected genomic sequence, which suggested strong purifying selection and small population sizes caused by bottlenecks. Recombination rates varied between the SCs but were lower than in other successful clones such as PMEN1. African isolates showed higher prevalence of antibiotic resistance genes than Asian isolates. Interestingly, certain West African isolates harbored a defective chloramphenicol and tetracycline resistance-conferring element (Tn5253) with a deletion in the loci encoding the chloramphenicol resistance gene (cat pC194), which caused lower chloramphenicol than tetracycline resistance. Furthermore, certain genes that promote colonisation were absent in the isolates, which may contribute to serotype 1's rarity in carriage and consequently its lower recombination rates.

CONCLUSIONS

The high phylogeographic diversity of the ST217 clone shows that this clone has been in circulation globally for a long time, which allowed its diversification and adaptation in different geographical regions. Such geographic adaptation reflects local variations in selection pressures in different locales. Further studies will be required to fully understand the biological mechanisms which makes the ST217 clone highly invasive but unable to successfully colonise the human nasopharynx for long durations which results in lower recombination rates.

Community-acquired bacterial meningitis

Meningitis is an inflammation of the meninges and subarachnoid space that can also involve the brain cortex and parenchyma. It can be acquired spontaneously in the community - community-acquired bacterial meningitis - or in the hospital as a complication of invasive procedures or head trauma (nosocomial bacterial meningitis). Despite advances in treatment and vaccinations, community-acquired bacterial meningitis remains one of the most important infectious diseases worldwide. Streptococcus pneumoniae and Neisseria meningitidis are the most common causative bacteria and are associated with high mortality and morbidity; vaccines targeting these organisms, which have designs similar to the successful vaccine that targets Haemophilus influenzae type b meningitis, are now being used in many routine vaccination programmes. Experimental and genetic association studies have increased our knowledge about the pathogenesis of bacterial meningitis. Early antibiotic treatment improves the outcome, but the growing emergence of drug resistance as well as shifts in the distribution of serotypes and groups are fuelling further development of new vaccines and treatment strategies. Corticosteroids were found to be beneficial in high-income countries depending on the bacterial species. Further improvements in the outcome are likely to come from dampening the host inflammatory response and implementing preventive measures, especially the development of new vaccines.

An outbreak of pneumococcal meningitis among older children (≥5 years) and adults after the implementation of an infant vaccination programme with the 13-valent pneumococcal conjugate vaccine in Ghana

BACKGROUND

An outbreak of pneumococcal meningitis among non-infant children and adults occurred in the Brong-Ahafo region of Ghana between December 2015 and April 2016 despite the recent nationwide implementation of a vaccination programme for infants with the 13-valent pneumococcal conjugate vaccine (PCV13).

METHODS

Cerebrospinal fluid (CSF) specimens were collected from patients with suspected meningitis in the Brong-Ahafo region. CSF specimens were subjected to Gram staining, culture and rapid antigen testing. Quantitative PCR was performed to identify pneumococcus, meningococcus and Haemophilus influenzae. Latex agglutination and molecular serotyping were performed on samples. Antibiogram and whole genome sequencing were performed on pneumococcal isolates.

RESULTS

Eight hundred eighty six patients were reported with suspected meningitis in the Brong-Ahafo region during the period of the outbreak. In the epicenter district, the prevalence was as high as 363 suspected cases per 100,000 people. Over 95 % of suspected cases occurred in non-infant children and adults, with a median age of 20 years. Bacterial meningitis was confirmed in just under a quarter of CSF specimens tested. Pneumococcus, meningococcus and Group B Streptococcus accounted for 77 %, 22 % and 1 % of confirmed cases respectively. The vast majority of serotyped pneumococci (80 %) belonged to serotype 1. Most of the pneumococcal isolates tested were susceptible to a broad range of antibiotics, with the exception of two pneumococcal serotype 1 strains that were resistant to both penicillin and trimethoprim-sulfamethoxazole. All sequenced pneumococcal serotype 1 strains belong to Sequence Type (ST) 303 in the hypervirulent ST217 clonal complex.

CONCLUSION

The occurrence of a pneumococcal serotype 1 meningitis outbreak three years after the introduction of PCV13 is alarming and calls for strengthening of meningitis surveillance and a re-evaluation of the current vaccination programme in high risk countries.

Serotype distribution and antimicrobial resistance of Streptococcus pneumoniae in children with acute bacterial meningitis in Mozambique: implications for a national immunization strategy

BACKGROUND

S. pneumoniae is the leading cause of acute bacterial meningitis (ABM) in children. Vaccination using the 10-valent conjugate vaccine (PCV-10) was recently introduced into the National Immunization Program in Mozambique, but data on serotype coverage of this vaccine formulation are scarce. In this study, we investigated the serotype distribution and antimicrobial resistance of isolates of S. pneumoniae causing ABM in children < 5 years at the two largest hospitals in Mozambique.

METHODS

Between March 2013 and March 2014, a total of 352 cerebrospinal fluid (CSF) samples were collected from eligible children, of which 119 (33.8 %) were positive for S. pneumoniae. Of these, only 50 samples met the criteria for serotyping and were subsequently serotyped using sequential multiplex PCR (SM-PCR), but 15 samples were non-typable.

RESULTS

The most common serotypes of S. pneumoniae were 1 (18.2 %), 5 (15.2 %), 14 (12.1 %), 9 V (12.1 %), 23 F (9.1 %), 6A (9.1 %), 4 (9.1 %) and 6B (6.1 %). Serotypes 1, 5, 9 V, 6A and 12 were mostly prevalent in Northern Mozambique, while serotypes 23 F, 4, 6B, 3 and 15B were predominant in Southern. Serotype coverage of PCV-10 and PCV-13 vaccine formulations were 81.8 % and 93.9 %, respectively. Serotypes 1, 3, 4, 6B, 14, 23 F were resistant to penicillin and sensitive to ceftriaxone.

CONCLUSIONS

Our findings shows that changing the current in use PCV-10 vaccine formulation to PCV-13 formulation might increase substantially the protection against invasive strains of S. pneumoniae as the PCV-10 vaccine formulation does not cover the serotypes 3 and 6A, which are prevalent in Mozambique.

Characterization of Spbhp-37, a Hemoglobin-Binding Protein of Streptococcus pneumoniae

Streptococcus pneumoniae is a Gram-positive microorganism that is the cause of bacterial pneumonia, sinusitis and otitis media. This human pathogen also can cause invasive diseases such as meningitis, bacteremia and septicemia. Hemoglobin (Hb) and haem can support the growth and viability of S. pneumoniae as sole iron sources. Unfortunately, the acquisition mechanism of Hb and haem in this bacterium has been poorly studied. Previously we identified two proteins of 37 and 22 kDa as putative Hb- and haem-binding proteins (Spbhp-37 and Spbhp-22, respectively). The sequence of Spbhp-37 protein was database annotated as lipoprotein without any function or localization. Here it was immunolocalized in the surface cell by transmission electron microscopy using specific antibodies produced against the recombinant protein. The expression of Spbhp-37 was increased when bacteria were grown in media culture supplied with Hb. In addition, the affinity of Sphbp-37 for Hb was determined. Thus, in this work we are presenting new findings that attempt to explain the mechanism involved in iron acquisition of this pathogen. In the future these results could help to develop new therapy targets in order to avoid the secondary effects caused by the traditional therapies.

Phylogenetic Analysis of Invasive Serotype 1 Pneumococcus in South Africa, 1989 to 2013

Serotype 1 is an important cause of invasive pneumococcal disease in South Africa and has declined following the introduction of the 13-valent pneumococcal conjugate vaccine in 2011. We genetically characterized 912 invasive serotype 1 isolates from 1989 to 2013. Simpson's diversity index (D) and recombination ratios were calculated. Factors associated with sequence types (STs) were assessed. Clonal complex 217 represented 96% (872/912) of the sampled isolates. Following the introduction of the 13-valent pneumococcal conjugate vaccine (PCV13), ST diversity increased in children <5 years (D, 0.39 to 0.63, P = 0.002) and individuals >14 years (D, 0.35 to 0.54, P < 0.001): ST-217 declined proportionately in children <5 years (153/203 [75%] versus 21/37 [57%], P = 0.027) and individuals >14 years (242/305 [79%] versus 96/148 [65%], P = 0.001), whereas ST-9067 increased (4/684 [0.6%] versus 24/228 [11%], P < 0.001). Three subclades were identified within ST-217: ST-217_C1 (353/382 [92%]), ST-217_C2 (15/382 [4%]), and ST-217_C3 (14/382 [4%]). ST-217_C2, ST-217_C3, and single-locus variant (SLV) ST-8314 (20/912 [2%]) were associated with nonsusceptibility to chloramphenicol, tetracycline, and co-trimoxazole. ST-8314 (20/912 [2%]) was also associated with increased nonsusceptibility to penicillin (P < 0.001). ST-217_C3 and newly reported ST-9067 had higher recombination ratios than those of ST-217_C1 (4.344 versus 0.091, P < 0.001; and 0.086 versus 0.013, P < 0.001, respectively). Increases in genetic diversity were noted post-PCV13, and lineages associated with antimicrobial nonsusceptibility were identified.

The Variable Region of Pneumococcal Pathogenicity Island 1 Is Responsible for Unusually High Virulence of a Serotype 1 Isolate

Streptococcus pneumoniae is the leading infectious cause of death in children in the world. However, the mechanisms that drive the progression from asymptomatic colonization to disease are poorly understood. Two virulence-associated genomic accessory regions (ARs) were deleted in a highly virulent serotype 1 clinical isolate (strain 4496) and examined for their contribution to pathogenesis. Deletion of a prophage encoding a platelet-binding protein (PblB) resulted in reduced adherence, biofilm formation, reduced initial infection within the lungs, and a reduction in the number of circulating platelets in infected mice. However, the region's overall contribution to the survival of mice was not significant. In contrast, deletion of the variable region of pneumococcal pathogenicity island 1 (vPPI1) was also responsible for a reduction in adherence and biofilm formation but also reduced survival and invasion of the pleural cavity, blood, and lungs. While the 4496ΔPPI1 strain induced higher expression of the genes encoding interleukin-10 (IL-10) and CD11b in the lungs of challenged mice than the wild-type strain, very few other genes exhibited altered expression. Moreover, while the level of IL-10 protein was increased in the lungs of 4496ΔPPI1 mutant-infected mice compared to strain 4496-infected mice, the levels of gamma interferon (IFN-γ), CXCL10, CCL2, and CCL4 were not different in the two groups. However, the 4496ΔPPI1 mutant was found to be more susceptible than the wild type to phagocytic killing by a macrophage-like cell line. Therefore, our data suggest that vPPI1 may be a major contributing factor to the heightened virulence of certain serotype 1 strains, possibly by influencing resistance to phagocytic killing.

Response thresholds for epidemic meningitis in sub-Saharan Africa following the introduction of MenAfriVac®

BACKGROUND

Since 2010, countries in the African meningitis belt have been introducing a new serogroup A meningococcal conjugate vaccine (MenAfriVac(®)) through mass campaigns. With the subsequent decline in meningitis due to Neisseria meningitidis serogroup A (NmA) and relative increase in meningitis due to other serogroups, mainly N. meningitidis serogroup W (NmW), the World Health Organisation (WHO) initiated a review of the incidence thresholds that guide response to meningitis epidemics in the African meningitis belt.

METHODS

Meningitis surveillance data from African meningitis belt countries from 2002 to 2013 were used to construct a single NmW dataset. The performance of different weekly attack rates, used as thresholds to initiate vaccination response, on preventing further cases was estimated. The cumulative seasonal attack rate used to define an epidemic was also varied.

RESULTS

Considerable variation in effect at different thresholds was observed. In predicting epidemics defined as a seasonal cumulative incidence of 100/10(5) population, an epidemic threshold of 10 cases/10(5) population/week performed well. Based on this same epidemic threshold, with a 6 week interval between crossing the epidemic threshold and population protection from a meningococcal vaccination campaign, an estimated 17 cases per event would be prevented by vaccination. Lowering the threshold increased the number of cases per event potentially prevented, as did shortening the response interval. If the interval was shortened to 4 weeks at the threshold of 10/10(5), the number of cases prevented would increase to 54 per event.

CONCLUSIONS

Accelerating time to vaccination could prevent more cases per event than lowering the threshold. Once the meningitis epidemic threshold is crossed, it is of critical importance that vaccination campaigns, where appropriate, are initiated rapidly.

Frequency of Pathogenic Paediatric Bacterial Meningitis in Mozambique: The Critical Role of Multiplex Real-Time Polymerase Chain Reaction to Estimate the Burden of Disease

BACKGROUND

In Sub-Saharan Africa, including Mozambique, acute bacterial meningitis (ABM) represents a main cause of childhood mortality. The burden of ABM is seriously underestimated because of the poor performance of culture sampling, the primary method of ABM surveillance in the region. Low quality cerebrospinal fluid (CSF) samples and frequent consumption of antibiotics prior to sample collection lead to a high rate of false-negative results. To our knowledge, this study is the first to determine the frequency of ABM in Mozambique using real-time polymerase chain reaction (qPCR) and to compare results to those of culture sampling.

METHOD

Between March 2013 and March 2014, CSF samples were collected at 3 regional hospitals from patients under 5 years of age, who met World Health Organization case definition criteria for ABM. Macroscopic examination, cytochemical study, culture, and qPCR were performed on all samples.

RESULTS

A total of 369 CSF samples were collected from children clinically suspected of ABM. qPCR showed a significantly higher detection rate of ABM-causing pathogens when compared to culture (52.3% [193/369] versus 7.3% [27/369], p = 0.000). The frequency of Streptococcus pneumoniae, Haemophilus influenzae, group B Streptococci, and Neisseria meningitidis were 32.8% (121⁄369), 12.2%, (45⁄369), 3.0% (16⁄369) and 4.3% (11⁄369), respectively, significantly higher compared to that obtained on culture (p < 0.001 for each).

CONCLUSION

Our findings demonstrate that culture is less effective for the diagnosis of ABM than qPCR. The common use of culture rather than qPCR to identify ABM results in serious underestimation of the burden of the disease, and our findings strongly suggest that qPCR should be incorporated into surveillance activities for ABM. In addition, our data showed that S. pneumoniae represents the most common cause of ABM in children under 5 years of age.

Virulence Factors of Streptococcus pneumoniae. Comparison between African and French Invasive Isolates and Implication for Future Vaccines

Background

Many surface proteins thought to promote Streptocococcus pneumoniae virulence have recently been discovered and are currently being considered as future vaccine targets. We assessed the prevalence of 16 virulence genes among 435 S. pneumoniae invasive isolates from France and the “African meningitis belt” region, with particular focus on serotype 1 (Sp1), to compare their geographical distribution, assess their association with site of infection and evaluate their potential interest as new vaccine candidates.

Methods

Detection by PCR of pspA (+families), pspC (+pspC.4), pavA, lytA, phtA,B,D,E, nanA,B,C, rrgA (Pilus-1), sipA (Pilus-2), pcpA and psrp was performed on all isolates, as well as antibiotic resistance testing and MLVA typing (+MLST on 54 representative strains). Determination of ply alleles was performed by sequencing (Sp1 isolates).

Results

MLVA and virulence genes profiles segregated Sp1 isolates into 2 groups that followed continent distribution. The ply allele 5 and most of the genes that were variable (nanC, Pilus-2, psrp, pcpA, phtD) were present in the French Sp1 isolates (PMEN clone Sweden¹-28, ST306) but absent from the African ones. Whereas all African Sp1 isolates clustered into a single MLST CC (CC217), MLVA distinguished two CCs that followed temporal evolution. Pilus-2 and psrp were more prevalent in bacteraemic pneumonia yielded isolates and phtB in meningitis-related isolates. Considering vaccine candidates, phtD was less prevalent than anticipated (50%) and pcpA varied importantly between France and Africa (98% versus 34%). Pilus-1 was carried by 7-11% of isolates and associated with β-lactams resistance.

Conclusions

Most virulence genes were carried by the European ST306 clone but were lacking on Sp1 isolates circulating in the African meningitis belt, where a more serious pattern of infection is observed. While virulence proteins are now considered as vaccine targets, the geographical differences in their prevalence could affect the efficacy expected from future vaccines.

Temporal changes in nasopharyngeal carriage of Streptococcus pneumoniae serotype 1 genotypes in healthy Gambians before and after the 7-valent pneumococcal conjugate vaccine

Streptococcus pneumoniae serotype 1 is one of the leading causes of invasive pneumococcal disease. However, this invasive serotype is hardly found in nasopharyngeal asymptomatic carriage and therefore large epidemiological studies are needed to assess the dynamics of serotype 1 infection. Within the context of a large cluster randomized trial conducted in rural Gambia to assess the impact of PCV-7 vaccination on nasopharyngeal carriage, we present an ancillary analysis describing the prevalence of nasopharyngeal carriage of pneumococcal serotype 1 and temporal changes of its more frequent genotypes. Nasopharyngeal swabs (NPS) were collected before PCV-7 vaccination (December 2003-May 2004) and up to 30 months after PCV-7 vaccination. The post-vaccination time was divided in three periods to ensure an equal distribution of the number of samples: (1) July 2006-March 2007, (2) April 2007-March 2008 and (3) April 2008-Feb 2009. S. pneumoniae serotype 1 were genotyped by MLST. Serotype 1 was recovered from 87 (0.71%) of 12,319 NPS samples collected. In the pre-vaccination period, prevalence of serotype 1 was 0.47% in both study arms. In the post-vaccination periods, prevalence in the fully vaccinated villages ranged between 0.08% in period 1 and 0.165% in period 2, while prevalence in partly vaccinated villages was between 0.17% in period 3 and 1.34% in period 2. Overall, four different genotypes were obtained, with ST3081 the most prevalent (60.71%), followed by ST618 (29.76%). ST3081 was found only in post-vaccination period 2 and 3, while ST618 had disappeared in post-vaccination period 3. Distribution of these major genotypes was similar in both study arms. Emergence of ST3081 and concomitant disappearance of ST618 may suggest a change in the molecular epidemiology of pneumococcal serotype 1 in this region. This change is not likely to be associated with the introduction of PCV-7 which lacks serotype 1, as it was observed simultaneously in both study arms. Future population-based epidemiological studies will provide further evidence of substantive changes in the pneumococcal serotype 1 epidemiology and the likely mechanisms.

Modified MLVA for Genotyping Queensland Invasive Streptococcus pneumoniae

Background

Globally, over 800 000 children under five die each year from infectious diseases caused by Streptococcus pneumoniae. To understand genetic relatedness between isolates, study transmission routes, assess the impact of human interventions e.g. vaccines, and determine infection sources, genotyping methods are required. The ‘gold standard’ genotyping method, Multi-Locus Sequence Typing (MLST), is useful for long-term and global studies. Another genotyping method, Multi-Locus Variable Number of Tandem Repeat Analysis (MLVA), has emerged as a more discriminatory, inexpensive and faster technique; however there is no universally accepted method and it is currently suitable for short-term and localised epidemiology studies. Currently Australia has no national MLST database, nor has it adopted any MLVA method for short-term or localised studies. This study aims to improve S. pneumoniae genotyping methods by modifying the existing MLVA techniques to be more discriminatory, faster, cheaper and technically less demanding than previously published MLVA methods and MLST.

Methods

Four different MLVA protocols, including a modified method, were applied to 317 isolates of serotyped invasive S. pneumoniae isolated from sterile body sites of Queensland children under 15 years from 2007–2012. MLST was applied to 202 isolates for comparison.

Results

The modified MLVA4 is significantly more discriminatory than the ‘gold standard’ MLST method. MLVA4 has similar discrimination compared to other MLVA techniques in this study). The failure to amplify particular loci in previous MLVA methods were minimised in MLVA4. Failure to amplify BOX-13 and Spneu19 were found to be serotype specific.

Conclusion

We have modified a highly discriminatory MLVA technique for genotyping Queensland invasive S. pneumoniae. MLVA4 has the ability to enhance our understanding of the pneumococcal epidemiology and the changing genetics of the pneumococcus in localised and short-term studies.

Genotyping Streptococcus pneumoniae

ABSTRACT 

Streptococcus pneumoniae is a potentially deadly human pathogen associated with high morbidity, mortality and global economic burden. The universally used bacterial genotyping methods are multilocus sequence typing and pulsed field gel electrophoresis. However, another highly discriminatory, rapid and less expensive genotyping technique, multilocus variable number of tandem repeat analysis (MLVA), has been developed. Unfortunately, no universal MLVA protocol exists, and some MLVA protocols do not amplify certain loci for all pneumococcal serotypes, leaving genotyping profiles incomplete. A number of other genotyping or characterization methods have been developed and will be discussed. This review examines the various protocols for genotyping S. pneumoniae and highlights the current direction technology and research is heading to understand this bacterium.

Predicting the impact of new pneumococcal conjugate vaccines: serotype composition is not enough

Streptococcus pneumoniae is a major cause of childhood morbidity and mortality worldwide. A heptavalent polysaccharide-protein conjugate vaccine (PCV) has proven highly effective in preventing pneumococcal disease in industrialized countries. Two higher-valent pneumococcal conjugate vaccines are now widely available, even in the poorest countries. These differ from each other in the number of serotypes and carrier proteins used for their conjugation. Some have assumed that the only meaningful clinical difference between PCV formulations is a function of the number of serotypes each contains. A careful review of recent clinical data with these and several unlicensed PCV formulations points to important similarities but also that some key properties of each vaccine likely differ from one another.

The impact of pneumolysin on the macrophage response to Streptococcus pneumoniae is strain-dependent

Streptococcus pneumoniae is the world's leading cause of pneumonia, bacteremia, meningitis and otitis media. A major pneumococcal virulence factor is the cholesterol-dependent cytolysin, which has the defining property of forming pores in cholesterol-containing membranes. In recent times a clinically significant and internationally successful serotype 1 ST306 clone has been found to express a non-cytolytic variant of Ply (Ply₃₀₆). However, while the pneumococcus is a naturally transformable organism, strains of the ST306 clonal group have to date been virtually impossible to transform, severely restricting efforts to understand the role of non-cytolytic Ply in the success of this clone. In this study isogenic Ply mutants were constructed in the D39 background and for the first time in the ST306 background (A0229467) to enable direct comparisons between Ply variants for their impact on the immune response in a macrophage-like cell line. Strains that expressed cytolytic Ply were found to induce a significant increase in IL-1β release from macrophage-like cells compared to the non-cytolytic and Ply-deficient strains in a background-independent manner, confirming the requirement for pore formation in the Ply-dependent activation of the NLRP3 inflammasome. However, cytolytic activity in the D39 background was found to induce increased expression of the genes encoding GM-CSF (CSF2), p19 subunit of IL-23 (IL23A) and IFNβ (IFNB1) compared to non-cytolytic and Ply-deficient D39 mutants, but had no effect in the A0229467 background. The impact of Ply on the immune response to the pneumococcus is highly dependent on the strain background, thus emphasising the importance of the interaction between specific virulence factors and other components of the genetic background of this organism.

Streptococcus pneumoniae invasive infections in Burkina Faso, 2007 to 2011

OBJECTIVE

We had for aim to determine the epidemiology of meningeal and lung invasive infections due to Streptococcus pneumoniae in Burkina Faso.

MATERIAL AND METHODS

We screened for S. pneumoniae with the usual bacteriology techniques and with real time polymerase chain reaction (rt-PCR) in 7917 samples of cerebrospinal fluid (CSF) and pleural fluid (PF) collected in the Ouagadougou Yalgado Ouedraogo Teaching Hospital, from 2007 to 2011.

RESULTS

S. pneumoniae was identified in 476 (6%) samples including 455 (5.7%) in CSF and 21 (0.3%) in PF. Sixty-seven percent of invasive infections occurred in patients 15 years of age or less, without any significant sex ratio difference. The infections occurred most frequently between January and August, with the first and most important peak between January and May (dry season) and the second peak between June and August (at the beginning of rain season). The introduction of rt-PCR proved the under diagnosing of invasive infections by usual bacteriological methods (latex agglutination assay and culture).

CONCLUSION

Invasive pneumococcal infections occur mainly in patients 15 years of age or less, without any difference in sex ratio and with peaks in the dry season. Vaccinal schedules should include all age ranges in Burkina Faso.