Polymerase chain reaction assay and bacterial meningitis surveillance in remote areas, Niger

Pediatric Bacterial Meningitis Surveillance in Niger: Increased Importance of Neisseria meningitidis Serogroup C, and a Decrease in Streptococcus pneumoniae Following 13-Valent Pneumococcal Conjugate Vaccine Introduction

BACKGROUND

Meningitis is endemic in Niger. Haemophilus influenzae type b (Hib) vaccine and the 13-valent pneumococcal conjugate vaccine (PCV13) were introduced in 2008 and 2014, respectively. Vaccination campaign against Neisseria meningitidis serogroup A was carried out in 2010-2011. We evaluated changes in pathogen distribution using data from hospital-based surveillance in Niger from 2010 through 2016.

METHODS

Cerebrospinal fluid (CSF) specimens from children <5 years old with suspected meningitis were tested to detect vaccine-preventable bacterial pathogens. Confirmatory identification and serotyping/grouping of Streptococcus pneumoniae, N. meningitidis, and H. influenzae were done. Antimicrobial susceptibility testing and whole genome sequencing were performed on S. pneumoniae isolates.

RESULTS

The surveillance included 2580 patients with suspected meningitis, of whom 80.8% (2085/2580) had CSF collected. Bacterial meningitis was confirmed in 273 patients: 48% (131/273) was N. meningitidis, 45% (123/273) S. pneumoniae, and 7% (19/273) H. influenzae. Streptococcus pneumoniae meningitis decreased from 34 in 2014, to 16 in 2016. PCV13 serotypes made up 88% (7/8) of S. pneumoniae meningitis prevaccination and 20% (5/20) postvaccination. Neisseria meningitidis serogroup C (NmC) was responsible for 59% (10/17) of serogrouped N. meningitidis meningitis. Hib caused 67% (2/3) of the H. influenzae meningitis isolates serotyped. Penicillin resistance was found in 16% (4/25) of S. pneumoniae isolates. Sequence type 217 was the most common lineage among S. pneumoniae isolates.

CONCLUSIONS

Neisseria meningitidis and S. pneumoniae remain important causes of meningitis in children in Niger. The decline in the numbers of S. pneumoniae meningitis post-PCV13 is encouraging and should continue to be monitored. NmC is the predominant serogroup causing N. meningitidis meningitis.

Characterization of pneumococcal meningitis before and after introduction of 13-valent pneumococcal conjugate vaccine in Niger, 2010-2018

Pneumococcal meningitis in the African meningitis belt is primarily caused by Streptococcus pneumoniae serotype 1, a serotype contained in the 13-valent pneumococcal conjugate vaccine (PCV13). In 2014, Niger introduced PCV13 with doses given at 6, 10, and 14 weeks of age. We leveraged existing meningitis surveillance data to describe pneumococcal meningitis trends in Niger. As a national reference laboratory for meningitis, Centre de Recherche Médicale et Sanitaire (CERMES) receives cerebrospinal fluid specimens from suspected bacterial meningitis cases and performs confirmatory testing for an etiology by culture or polymerase chain reaction (PCR). Specimens with S. pneumoniae detection during 2010-2018 were sent to the Centers for Disease Control and Prevention for serotyping by sequential triplex real-time PCR. Specimens that were non-typeable by real-time PCR underwent serotyping by conventional multiplex PCR. We tested differences in the distribution of pneumococcal serotypes before (2010-2012) and after (2016-2018) PCV13 introduction. During January 2010 to December 2018, CERMES received 16,155 specimens; 5,651 (35%) had bacterial etiology confirmed. S. pneumoniae accounted for 13.2% (744/5,651); 53.1% (395/744) were serotyped. During 2010-12, PCV13-associated serotypes (VT) constituted three-fourths of serotyped pneumococcus-positive specimens; this proportion declined in all age groups in 2016-18, most substantially in children aged < 5 years (74.0% to 28.1%; P < 0.05). Among persons aged ≥ 5 years, VT constituted > 50% of pneumococcal meningitis after PCV13 introduction; serotype 1 remained the most common VT among persons aged ≥ 5 years, but not among those < 5 years. VT as a group caused a smaller proportion of reported pneumococcal meningitis cases after PCV13 introduction in Niger. Serotype 1, however, remains the major cause of pneumococcal meningitis in older children and adults. Different vaccination strategies, such as changing the infant vaccination schedule or extending vaccine coverage to older children and adults, are needed, in addition to stronger surveillance.

Epidemiology of Bacterial Meningitis in the Nine Years Since Meningococcal Serogroup A Conjugate Vaccine Introduction, Niger, 2010-2018

BACKGROUND

In 2010, Niger and other meningitis belt countries introduced a meningococcal serogroup A conjugate vaccine (MACV). We describe the epidemiology of bacterial meningitis in Niger from 2010 to 2018.

METHODS

Suspected and confirmed meningitis cases from January 1, 2010 to July 15, 2018 were obtained from national aggregate and laboratory surveillance. Cerebrospinal fluid specimens were analyzed by culture and/or polymerase chain reaction. Annual incidence was calculated as cases per 100 000 population. Selected isolates obtained during 2016-2017 were characterized by whole-genome sequencing.

RESULTS

Of the 21 142 suspected cases of meningitis, 5590 were confirmed: Neisseria meningitidis ([Nm] 85%), Streptococcus pneumoniae ([Sp] 13%), and Haemophilus influenzae ([Hi] 2%). No NmA cases occurred after 2011. Annual incidence per 100 000 population was more dynamic for Nm (0.06-7.71) than for Sp (0.18-0.70) and Hi (0.01-0.23). The predominant Nm serogroups varied over time (NmW in 2010-2011, NmC in 2015-2018, and both NmC and NmX in 2017-2018). Meningococcal meningitis incidence was highest in the regions of Niamey, Tillabery, Dosso, Tahoua, and Maradi. The NmW isolates were clonal complex (CC)11, NmX were CC181, and NmC were CC10217.

CONCLUSIONS

After MACV introduction, we observed an absence of NmA, the emergence and continuing burden of NmC, and an increase in NmX. Niger's dynamic Nm serogroup distribution highlights the need for strong surveillance programs to inform vaccine policy.

Evaluation of response strategies against epidemics due to Neisseria meningitidis C in Niger

OBJECTIVE

To inform public health recommendations, we evaluated the effectiveness and efficiency of current and hypothetical surveillance and vaccine response strategies against Neisseria meningitidis C meningitis epidemics in 2015 in Niger.

METHODS

We analysed reports of suspected and confirmed cases of meningitis from the region of Dosso during 2014 and 2015. Based on a definition of epidemic signals, the effectiveness and efficiency of surveillance and vaccine response strategies were evaluated by calculating the number of potentially vaccine-preventable cases and number of vaccine doses needed per epidemic signal.

RESULTS

A total of 4763 weekly health area reports, collected in 90 health areas with 1282 suspected meningitis cases, were included. At a threshold of 10 per 100 000, the total number of estimated vaccine-preventable cases was 29 with district-level surveillance and vaccine response, 141 with health area-level surveillance and vaccination and 339 with health area-level surveillance and district-level vaccination. While being most effective, the latter strategy required the largest number of vaccine doses (1.8 million), similar to the strategy of surveillance and vaccination at district level (1.3 million), whereas the strategy of surveillance and vaccination at health area level would have required only 0.8 million doses. Thus, efficiency was lowest for district-level surveillance and highest for health area-level surveillance with district-level vaccination.

CONCLUSION

In this analysis, we found that effectiveness and efficiency were higher at health area-level surveillance and district-level vaccination than for other strategies. Use of N. meningitidis C vaccines in a preventive strategy thus should be considered, in particular as most reactive vaccine response strategies in our analysis had little impact on disease burden.

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.

Evolution of meningococcal carriage in serogroups X and Y before introduction of MenAfriVac in the health district of Kaya, Burkina Faso

BACKGROUND

The objective of this study was to evaluate the carriage of Neisseria meningitidis (Nm) serogroups X and Y in the health district of Kaya before the introduction of a serogroup A meningococcal conjugate vaccine in Burkina Faso.

METHODS

A repeated cross-sectional meningococcal carriage study was conducted in 2009 in eight randomly selected villages in the health district of Kaya, Burkina Faso. In each of 4 sampling rounds at least 1,500 people were enrolled within a 1-month period.

RESULTS

From a total of 6,686 throat swabs we identified 419 Nm isolates (6.27%). The dominating serogroups were Y (3.19%) and X (1.05%). Overall carriage was higher in the dry season compared with the rainy season (OR, 1.51; 95% CI, 1.06-2.16). Carriage prevalence of serogroups Y and X varied by round and was highest at the end of the dry season (4.92% and 1.22%, respectively). The only risk factor associated with NmX carriage was vaccination status in contrast to serogroup Y, which was associated with age groups 5-9 years and 10-14 years.

CONCLUSION

The presence of Nm serogroups X and Y, which could replace or be added to the serogroup A, is a warning sign. There is a need to strengthen surveillance and laboratory diagnosis of the various meningococcal serogroups circulating in Africa.

Treatment and prevention strategies to combat pediatric pneumococcal meningitis

Pneumococcal meningitis is a severe, life-threatening infection of the nervous system affecting infants, children and adults alike. The incidence of pneumococcal meningitis in infants and children less than 2 years of age in Europe is approximately 10 out of 100,000 per year, rising to approximately 148 out of 100,000 per year in Gambian infants. The use of highly sensitive tests such as PCR may increase the likelihood of detecting the infection by 20% or more. Epidemics of serotype 1 pneumococcal meningitis in northern Ghana, have had many of the characteristics of meningococcal meningitis epidemics. Neurologic sequelae may occur in 28-63% of cases, and serotype 3 is associated with a 2.54 relative risk of death. The pathogenic process can be divided into invasion, inflammatory pathways, bacterial toxicity and damage; pneumolysin being particularly associated with apoptosis. In the future, neuroprotection may be achieved, targeting this process at all these levels. Therapeutic guidelines have been published by the Infectious Diseases Society of America. Standard empiric therapy, in those aged greater than or equal to 1 month, is a third-generation cephalosporin plus vancomycin. There is insufficient evidence relating to the use or otherwise of corticosteroids in pneumococcal meningitis to make a firm recommendation. The advent of a pneumococcal conjugate vaccine is the most powerful tool available for the prevention of pneumococcal meningitis in all parts of the world.

Meningococcal serogroup W135 in the African meningitis belt: epidemiology, immunity and vaccines

In the sub-Saharan African meningitis belt there is a region of hyperendemic and epidemic meningitis stretching from Senegal to Ethiopia. The public health approaches to meningitis epidemics, including those related to vaccine use, have assumed that Neisseria meningitidis serogroup A will cause the most disease. During 2001 and 2002, the first large-scale epidemics of serogroup W135 meningitis in sub-Saharan Africa were reported from Burkina Faso. The occurrence of N. meningitidis W135 epidemics has led to a host of new issues, including the need for improved laboratory diagnostics for identifying serogroups during epidemics, an affordable supply of serogroup W135-containing polysaccharide vaccine for epidemic control where needed, and re-evaluating the long-term strategy of developing a monovalent A conjugate vaccine for the region. This review summarizes the existing data on N. meningitidis W135 epidemiology, immunology and vaccines as they relate to meningitis in sub-Saharan Africa.

Epidemiologic pattern of meningococcal meningitis in northern Cameroon in 2007-2010: contribution of PCR-enhanced surveillance

OBJECTIVES

Monitoring acute bacterial meningitis in northern Cameroon.

METHODS

Health professionals collected cerebrospinal fluid (CSF) specimens from patients presenting with clinical symptoms of meningitis. Specimens were tested using gram stain, latex agglutination test, and culture. A PCR assay completed the diagnostic testing. Multilocus sequence typing (MLST) was performed on some Neisseria meningitidis (Nm) isolates.

RESULTS

From 2007 through 2010, of the 1429 CSF specimens tested, 292 (20·4%) were positive, either for Nm (205), Streptococcus pneumoniae (Sp) (57), or Haemophilus influenzae (Hi) (30). From 2007 through 2009, the serogroup W135 represented 98·8% of 164 case isolates. Until 2008, most serogroup W135 isolates presented the sequence-type ST-2881 usually associated with sporadic cases. Since 2009, the ST-11 (an epidemic-associated clone) became predominant, although no epidemic occurred. Serogroup A ST-7 was observed in 2010 and caused a localized epidemic. Using the detection PCR on turbid CSF, a 2·7-fold increase in cases with etiologic diagnosis was obtained, compared to culture. All tested meningococcal isolates (42) were susceptible to ampicillin, chloramphenicol, and cefotaxim.

CONCLUSIONS

Resurgence of serogroup A and recent increase in ST-11 among serogroup W135 isolates were worrying when considered with the epidemic wave of serogroup A meningitis, which affected neighboring countries and the serogroup W135 epidemic in Niger in 2009-2010.

Determination of pneumococcal serotypes in meningitis cases in Niger, 2003-2011

Background

The epidemiology of pneumococcal meningitis in the African ‘meningitis belt’ is poorly studied. In order to ensure an effective vaccination strategy and post-vaccination surveillance, we examined the serotype distribution patterns of pneumococcal meningitis in Niger over the period 2003–2011.

Methods

Cerebrospinal fluid (CSF) samples were collected from different health facilities throughout Niger in the frame of the national microbiological surveillance of meningitis. Determination of the serotype of CSF positive for pneumococci was performed using a sequential multiplex PCR method (SM-PCR) adapted with a national algorithm in which 32 different serotypes were covered and grouped into eight consecutive PCR.

Results

The SM-PCR assay could predict the Sp serotype for 779 CSF (88.7%), 98 CSF (11.3%) were not-typeable in our national-adapted algorithm. In total, 26 different serotypes were identified. Serotype 1 (n = 393) was the most prevalent and accounted for 45.3% of infections, followed by serogroups/serotypes 12F/(12A)/(44)/(46) (7.3%), 6/(6A/6B/6C/6D) (5.4%), 14 (5.2%), 5 (4.6%), 23F (4.2%), 45 (3.6%), 2 (3.1%), 18/(18A/18B/18C/18F) (2.9%) and 17 others serotypes with a prevalence of less than 2%. The proportion of serotype 1 in infants(<2 years old) represented only 4.3% of the cases affected by this serotype. In contrast, serotypes 5, 6, 14, 19A and 23F were only detected in very young children.

Conclusions

The proportion of serotype 1 in the pneumococcal meningitis cases and the theoretical vaccine coverage across all age groups advocates for the introduction of a conjugate vaccine (PCV10 or 13) into the Expanded Programme on Immunization (EPI) in Niger. Post-vaccine introduction surveillance supported by molecular approaches will be essential to provide a comprehensive picture of the impact of the vaccine on the burden reduction of pneumococcal meningitis and on pneumococcal serotype distribution.

A broad range assay for rapid detection and etiologic characterization of bacterial meningitis: performance testing in samples from sub-Sahara

This study aimed to conduct a pilot evaluation of broad-based multiprobe polymerase chain reaction (PCR) in clinical cerebrospinal fluid (CSF) samples compared to local conventional PCR/culture methods used for bacterial meningitis surveillance. A previously described PCR consisting of initial broad-based detection of Eubacteriales by a universal probe, followed by Gram typing, and pathogen-specific probes was designed targeting variable regions of the 16S rRNA gene. The diagnostic performance of the 16S rRNA assay in ""127 CSF samples was evaluated in samples from patients from Togo, Africa, by comparison to conventional PCR/culture methods. Our probes detected Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. Uniprobe sensitivity and specificity versus conventional PCR were 100% and 54.6%, respectively. Sensitivity and specificity of uniprobe versus culture methods were 96.5% and 52.5%, respectively. Gram-typing probes correctly typed 98.8% (82/83) and pathogen-specific probes identified 96.4% (80/83) of the positives. This broad-based PCR algorithm successfully detected and provided species level information for multiple bacterial meningitis agents in clinical samples.

Analysing spatio-temporal clustering of meningococcal meningitis outbreaks in Niger reveals opportunities for improved disease control

BACKGROUND

Meningococcal meningitis is a major health problem in the "African Meningitis Belt" where recurrent epidemics occur during the hot, dry season. In Niger, a central country belonging to the Meningitis Belt, reported meningitis cases varied between 1,000 and 13,000 from 2003 to 2009, with a case-fatality rate of 5-15%.

METHODOLOGY/PRINCIPAL FINDINGS

In order to gain insight in the epidemiology of meningococcal meningitis in Niger and to improve control strategies, the emergence of the epidemics and their diffusion patterns at a fine spatial scale have been investigated. A statistical analysis of the spatio-temporal distribution of confirmed meningococcal meningitis cases was performed between 2002 and 2009, based on health centre catchment areas (HCCAs) as spatial units. Anselin's local Moran's I test for spatial autocorrelation and Kulldorff's spatial scan statistic were used to identify spatial and spatio-temporal clusters of cases. Spatial clusters were detected every year and most frequently occurred within nine southern districts. Clusters most often encompassed few HCCAs within a district, without expanding to the entire district. Besides, strong intra-district heterogeneity and inter-annual variability in the spatio-temporal epidemic patterns were observed. To further investigate the benefit of using a finer spatial scale for surveillance and disease control, we compared timeliness of epidemic detection at the HCCA level versus district level and showed that a decision based on threshold estimated at the HCCA level may lead to earlier detection of outbreaks.

CONCLUSIONS/SIGNIFICANCE

Our findings provide an evidence-based approach to improve control of meningitis in sub-Saharan Africa. First, they can assist public health authorities in Niger to better adjust allocation of resources (antibiotics, rapid diagnostic tests and medical staff). Then, this spatio-temporal analysis showed that surveillance at a finer spatial scale (HCCA) would be more efficient for public health response: outbreaks would be detected earlier and reactive vaccination would be better targeted.

Diagnosis of Streptococcus pneumoniae and Haemophilus influenzae type b meningitis by identifying DNA from cerebrospinal fluid-impregnated filter paper strips

BACKGROUND

Bacterial meningitis remains often etiologically unconfirmed, especially in resource-poor settings. We tested the potential of real-time polymerase chain reaction to identify Streptococcus pneumoniae (Pnc) and Haemophilus influenzae type b (Hib) from cerebrospinal fluid impregnated on filter paper strips.

METHODS

Pnc and Hib genome equivalents were blindly quantified by polymerase chain reaction from 129 liquid cerebrospinal fluid (CSF) samples-the standard-and strips stored at room temperature for months. Genome counts were compared by simple regression.

RESULTS

The strips showed a sensitivity and specificity of 92% and 99% for Pnc, and of 70% and 100% for Hib, respectively. The positive and negative predictive values were 94% and 97% for Pnc, and 100% and 89% for Hib, respectively. For Pnc, the positive and negative likelihood ratio was 92 and 0.08, and the overall accuracy 98%, whereas for Hib they were 70 and 0.30, and 91%, respectively. Genome counting showed good correlation between the filter paper and liquid CSF samples, r(2) being 0.87 for Pnc and 0.68 for Hib (P < 0.0001 for both).

CONCLUSION

Although not replacing bacterial culture, filter paper strips offer an easy way to collect and store CSF samples for later bacteriology. They can also be transported in standard envelops by regular mail.

[Effectiveness of a polymerase chain reaction using seminested and multiplex strategy for the identification of the three main bacteria responsible for meningitis in Burkina Faso]

A prospective study (from August 2006 to April 2007) was carried out with 214 cerebrospinal fluid samples with suspicion of bacterial meningitis. The aim of the study was to assess the effectiveness of the simultaneous detection of Neisseria meningitidis, Streptococcus sp. and Haemophilus influenzae using seminested polymerase chain reaction strategy. Among the 214 samples tested by both PCR and culture, the overall confirmation rate was 64% for PCR and 40.1% for culture (P = 2 x 10⁻⁶). Taking culture method as the standard reference, the overall sensitivity of PCR was 98.8% and specificity, 59.4%. The sensitivity of PCR was 100, 97.3 and 100% respectively for N. meningitidis, Streptococcus sp. and H. influenzae with respective specificities of 70, 93.2 and 97.2%. In conclusion, the seminested PCR strategy is a sensitive method and it can be implemented in the reference public health laboratories for an exhaustive microbiological surveillance of bacterial meningitis.

Field evaluation of two rapid diagnostic tests for Neisseria meningitidis serogroup A during the 2006 outbreak in Niger

The Pastorex((R)) (BioRad) rapid agglutination test is one of the main rapid diagnostic tests (RDTs) for meningococcal disease currently in use in the "meningitis belt". Earlier evaluations, performed after heating and centrifugation of cerebrospinal fluid (CSF) samples, under good laboratory conditions, showed high sensitivity and specificity. However, during an epidemic, the test may be used without prior sample preparation. Recently a new, easy-to-use dipstick RDT for meningococcal disease detection on CSF was developed by the Centre de Recherche Médicale et Sanitaire in Niger and the Pasteur Institute in France. We estimate diagnostic accuracy in the field during the 2006 outbreak of Neisseria meningitidis serogroup A in Maradi, Niger, for the dipstick RDT and Pastorex((R)) on unprepared CSF, (a) by comparing each test's sensitivity and specificity with previously reported values; and (b) by comparing results for each test on paired samples, using McNemar's test. We also (c) estimate diagnostic accuracy of the dipstick RDT on diluted whole blood. We tested unprepared CSF and diluted whole blood from 126 patients with suspected meningococcal disease presenting at four health posts. (a) Pastorex((R)) sensitivity (69%; 95%CI 57-79) was significantly lower than found previously for prepared CSF samples [87% (81-91); or 88% (85-91)], as was specificity [81% (95%CI 68-91) vs 93% (90-95); or 93% (87-96)]. Sensitivity of the dipstick RDT [89% (95%CI 80-95)] was similar to previously reported values for ideal laboratory conditions [89% (84-93) and 94% (90-96)]. Specificity, at 62% (95%CI 48-75), was significantly lower than found previously [94% (92-96) and 97% (94-99)]. (b) McNemar's test for the dipstick RDT vs Pastorex((R)) was statistically significant (p<0.001). (c) The dipstick RDT did not perform satisfactorily on diluted whole blood (sensitivity 73%; specificity 57%).Sensitivity and specificity of Pastorex((R)) without prior CSF preparation were poorer than previously reported results from prepared samples; therefore we caution against using this test during an epidemic if sample preparation is not possible. For the dipstick RDT, sensitivity was similar to, while specificity was not as high as previously reported during a more stable context. Further studies are needed to evaluate its field performance, especially for different populations and other serogroups.

The epidemiology of Neisseria meningitidis meningitis in Togo during 2003–2005

Few reports documenting the epidemiology of Neisseria meningitidis (Nm) serogroup W135 exist, and none from Togo. During 2003-2005, we conducted acute bacterial meningitis surveillance at three major reference hospitals in Togo. Of 116 Nm identified, 83 (71%) were NmA, 23 (20%) were NmW135, and 10 (9%) did not have a serogroup identified. Nine percent of NmW135 cases and 35% of NmA cases occurred among those aged 15 years or older. The two hospitals in central Togo reported 23% of all Nm cases and 78% of NmW135 cases. Twelve of the 23 NmW135 cases occurred during February-March 2003, while the remaining 11 occurred sporadically over the remaining 18 months of the study. NmW135 meningitis showed pronounced temporal and geographic clustering and occurred almost exclusively among those younger than 15 years old. By the 2004-2005 epidemic season, NmW135 had largely disappeared from Togo for unknown reasons.

Populations of pharyngeal meningococci in Niger

This study investigated the carriage of Neisseria meningitidis group W135 (NmW135) belonging to sequence type (ST)-2881, ST-11 and NmA ST-7, as these three lineages have been responsible for sporadic cases in 2003 in Niamey (Niger). ST-7 and ST-11 were also the two genotypes involved in recent outbreaks in the African meningitis belt. Among the 97 Nm isolates obtained from 287 schoolchildren swabbed three times, 1 was identified as NmA, 34 as NmW135, 8 as NmY and 54 were non-groupable (NG). Among the 86 isolates genotyped, 59.3% belonged to ST-192, 24.4% to ST-2881, 5.8% to ST-2880, 4.6% to ST-175, 3.5% to ST-4899, 1.2% to ST-11 and 1.2% to ST-7. Most of the isolates recovered were weakly pathogenic Nm NG ST-192 and NmW135 ST-2881. These results, although preliminary, are important to consider before introduction of a NmA conjugate meningococcal vaccine in Africa.

Risk mapping and early warning systems for the control of meningitis in Africa

Epidemics of meningococcal meningitis in Africa have plagued the continent for over a century. These epidemics have a strong association with the environment and efforts are being made to develop models to predict both their location and their incidence. This review describes the predictive models based on climate/environmental information currently available, describes work in progress, and presents evidence that the distribution of the epidemics is changing in a pattern that is compatible with changes in the environment. Discussion of priorities for research in the context of the new conjugate vaccines in Africa is also provided.

Case-fatality ratio of bacterial meningitis in the African meningitis belt: we can do better

In the African meningitis belt, reported case-fatality ratio (CFR) for meningitis are usually calculated on the basis of presumed cases. We reviewed 3509 presumed cases of bacterial meningitis reported in Niger for which a cerebrospinal fluid (CSF) sample had been tested later at the reference laboratory. The main aetiologies were Neisseria meningitidis (1496 cases), Streptococcus pneumoniae (303 cases) and Haemophilus influenzae (105 cases). The CFR of meningococcal meningitis was lower for serogroup A (5.5%) than for serogroups X (12%) and W135 (12.7%). With a CFR of 49.8%, pneumococcal meningitis, albeit representing only 20.7% of confirmed cases, accounted for 50% of the deaths. The disease burden of pneumococcal meningitis must be better taken into consideration in the future. As most treatments are presumptive, there is a urgent need for an easy-to-administer, cheap first-line treatment effective on N. meningitidis as well as on S. pneumoniae and H. influenzae that would replace the single-dose oily chloramphenicol treatment which is the most frequent treatment administered today, independent of microbial aetiology and season. The development of diagnostic tools really suitable for remote health facilities also is an urgent challenge.

Meningococcal meningitis: unprecedented incidence of serogroup X-related cases in 2006 in Niger

BACKGROUND

In Niger, epidemic meningococcal meningitis is primarily caused by Neisseria meningitidis (Nm) serogroup A. However, since 2002, Nm serogroup W135 has been considered to be a major threat that has not yet been realized, and an unprecedented incidence of Nm serogroup X (NmX) meningitis was observed in 2006.

METHODS

Meningitis surveillance in Niger is performed on the basis of reporting of clinically suspected cases. Cerebrospinal fluid specimens are sent to the reference laboratory in Niamey, Niger. Culture, latex agglutination, and polymerase chain reaction are used whenever appropriate. Since 2004, after the addition of a polymerase chain reaction-based nonculture assay that was developed to genogroup isolates of NmX, polymerase chain reaction testing allows for the identification of Nm serogroup A, Nm serogroup B, Nm serogroup C, NmX, Nm serogroup Y, and Nm serogroup W135.

RESULTS

From January to June 2006, a total of 4185 cases of meningitis were reported, and 2905 cerebrospinal fluid specimens were laboratory tested. NmX meningitis represented 51% of 1139 confirmed cases of meningococcal meningitis, but in southwestern Niger, it represented 90%. In the agglomeration of Niamey, the reported cumulative incidence of meningitis was 73 cases per 100,000 population and the cumulative incidence of confirmed NmX meningitis was 27.5 cases per 100,000 population (74.6 cases per 100,000 population in children aged 5-9 years). NmX isolates had the same phenotype (X : NT : P1.5), and all belonged to the same sequence type (ST-181) as the NmX isolates that were circulating in Niamey in the 1990s. Nm serogroup W135 represented only 2.1% of identified meningococci.

CONCLUSIONS

This is, to our knowledge, the first report of such a high incidence of NmX meningitis, although an unusually high incidence of NmX meningitis was also observed in the 1990s in Niamey. The increasing incidence of NmX meningitis is worrisome, because no vaccine has been developed against this serogroup. Countries in the African meningitis belt must prepare to face this potential new challenge.

Quality assessed nonculture techniques for detection and typing of meningococci

PCR protocols are increasingly used in laboratories worldwide for the diagnosis and confirmation of invasive meningococcal infection. Protocols are now available for the identification of Neisseria meningitidis, for genogrouping, susceptibility to antibiotics and genotyping of the corresponding isolates. The implementation of quality assurance (QA) schemes and standardization of protocols are required. Diagnostic and confirmatory PCRs should perform consistently in clinical and reference microbiology laboratories. General QA schemes address the issues of sample preparation, PCR laboratory environment, equipment and validation of protocols. Moreover, external QA interlaboratory studies are essential. The European Monitoring Group on Meningococci has provided a good forum to conduct such studies through the development and distribution of samples and protocols for nonculture detection and typing of N. meningitidis.

Carriage of Neisseria meningitidis serogroup W135 ST-2881

Serogroup W135 ST-2881 meningococci caused a cluster of meningitis cases in Niger in 2003. Of 80 healthy persons in the patients' villages, 28 (35%) carried meningococci; 20 of 21 W135 carrier strains were ST-2881. Ten months later, 5 former carriers were still carriers of W135 ST-2881 strains. The serum bactericidal antibody activity changed according to carrier status.

High sensitivity and specificity of the Pastorex® latex agglutination test for Neisseria meningitidis serogroup A during a clinical trial in Niger

There is a great need for a rapid diagnostic test to guide vaccine choice during outbreaks of meningococcal meningitis in resource-poor countries. During a randomised clinical trial conducted during an epidemic of Neisseria meningitidis serogroup A in Niger in 2003, the sensitivity and specificity of the Pastorex latex agglutination test for this serogroup under optimal field conditions were assessed, using culture and/or PCR as the gold standard. Results from 484 samples showed a sensitivity of 88% (95% CI 85-91%) and a specificity of 93% (95% CI 90-95%). Pastorex could be a good alternative to current methods, as it can be performed in a local laboratory with rapid results and is highly specific. Sensitivity can be improved with prior microscopy where feasible. A study specifically to evaluate the Pastorex test under epidemic conditions, using laboratories with limited resources, is recommended.

Diagnosis of Streptococcus pneumoniae meningitis by polymerase chain reaction amplification of the gene for pneumolysin

Diagnosis of bacterial meningitis has long been based on classical methods of Gram stain, serological tests, and culture of cerebrospinal fluid (CSF). The performance of these methods, especially culture and direct smear is thwarted by failure to detect bacteria following administration of antimicrobial agents and reluctance to performance lumbar punctures at admission. Indeed, patients with meningitis frequently receive antibiotics orally or by injection before the diagnosis is suspected or established Thus an alternative method has become necessary to help clinicians and epidemiologists to management and control of bacterial meningitis. We evaluate the application of a polymerase chain reaction-based (PCR) assay for amplification of pneumolysin gene (ply) to diagnosis of Streptococcus pneumoniae meningitis. The PCR assay sensitivity for CSF was 96% (95% confidence interval, CI, 90-99%) compared to a sensitivity of 59% for culture (95% CI 49-69%), 66% for Gram stain (95% CI 56-74%), and 78% for latex agglutination test (95% CI 69-86%); PCR specificity was 100% (95% CI 83-100%). PCR results were available within 4 h of the start of the assay. This molecular approach proved to be reliable and useful to identify this bacterium compared with other classical laboratory methods for identification of bacterial meningitis pathogens.

Scaling up of PCR-based surveillance of bacterial meningitis in the African meningitis belt: indisputable benefits of multiplex PCR assay in Niger

The absence of reliable laboratories for culture of Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae, the three main causes of bacterial meningitis in Africa, hampers microbiological surveillance in these countries. To compensate for this situation in Niger, a multiplex single-tube PCR method has been implemented at a central level to test cerebrospinal fluid (CSF) samples. The overall confirmation rate for PCR (N=3791) was 40.8% compared with 16.0% for culture (N=945) (P<10(-6)). Among 850 CSF specimens tested by both methods, the overall confirmation rate was 29.4% for PCR and 16.4% for culture (P<10(-8)). PCR was also efficient for the CSF specimens stored in Trans-isolate medium. In conclusion, PCR assay is currently a key tool in Africa to improve microbiological surveillance of bacterial meningitis.

Evaluation of the Pastorex meningitis kit for the rapid identification of Neisseria meningitidis serogroups A and W135

The recent emergence of Neisseria meningitidis W135 as a cause of epidemic bacterial meningitis and the availability of a trivalent ACW135 vaccine have created a need for accurate and timely meningococcal serogroup determination for organization of epidemic vaccine response. The sensitivity and specificity of the Pastorex meningitis kit (Bio-Rad) to identify serogroups A and W135 in the African meningitis belt was assessed using PCR testing as the gold standard. The sensitivity and specificity for serogroups A and W135 were 87 and 85%, respectively, while the specificities were 93 and 97%. The positive and negative likelihood ratios for A were 12 and 0.14 and for W135 were 33 and 0.16. The positive and negative predictive values, computed to simulate an epidemic of meningococcal meningitis with an estimated 70% prevalence of N. meningitidis among suspected cases, were 97% and 75% for A and 99% and 73% for W135. In remote locations of the African meningitis belt, latex agglutination is the only currently available test that can rapidly determine meningococcal serogroup. This study showed that latex agglutination performs well and could be used during the epidemic season to determine appropriate vaccine response.

Evaluation of blood culture bottles seeded with X-V factors for the detection of Neisseria meningitidis and Haemophilus influenzae

The purpose of this in vitro study was to determine the ability of seeded and not-seeded commercial pediatric blood culture bottles to support the growth of the most frequently responsible microorganisms for bacterial meningitides (Neisseria meningitidis, and Haemophilus influenzae). Tests have been carried out with an automated colorimetric pediatric blood culture system, BacTAlert, Organon Teknika. Bottles were inoculated with X-V factors and serial dilutions of the each bacterium in six times (10(1)-10(6) colony forming unit [CFU]/ml). The bottles, which were supplemented with X-V factors, proved to be effective and time to detection (TTD) was shorter than the un-seeded bottles (p0.05). Time difference between seeded and not-seeded bottles was getting greater at high dilutions of both bacteria. We consider that in presence of a few bacteria, the seeding of bottles with X-V factors is very critical obtaining N. meningitidis, and H. influenzae as the causative agents of meningitidis. The recovery rate of the microorganisms, which were isolated from cerebrospinal fluid by using the X-V factor-seeded blood culture bottles, is therefore higher than with the conventional culture methods.

Epidemiological patterns of meningococcal meningitis in Niger in 2003 and 2004: under the threat of N. meningitidis serogroup W135

Since the Neisseria meningitidis serogroup W135 epidemic in Burkina Faso in 2002, the neighbouring countries dread undergoing outbreaks. Niger has strongly enhanced the microbiological surveillance, especially by adding the polymerase chain reaction (PCR) assay to the national framework of the surveillance system. During the 2003 epidemic season, 8113 clinically suspected cases of meningitis were notified and nine districts of the 42 crossed the epidemic threshold, while during the 2004 season, the number of cases was 3521 and four districts notified epidemics. In 2003 and 2004, serogroup A was identified in most N. meningitidis from cerebrospinal fluid (CSF) specimens (89.7% of 759 and 87.2% of 406, respectively). Although serogroup W135 represented only 8.3% of the meningococcal meningitis in 2003 and 7.9% in 2004, and was not involved in outbreaks, it was widespread in various areas of the country. In the regions that notified epidemics, the proportion of serogroup W135 was tiny while it exceeded 40% in several non-epidemic regions. Despite the wide distribution of W135 serogroup in Niger and the fears expressed in 2001, the threat of a large epidemic caused by N. meningitidis W135 seems to have been averted in Niger so far. There is no clear indication whether this serogroup will play a lasting role in the epidemiology of meningococcal meningitis or not. As early as in the 1990s, a significant but transient increase in the incidence of N. meningitidis serogroup X was observed. Close microbiological surveillance is crucial for monitoring the threat and for identifying at the earliest the serogroups involved in epidemics.

Molecular epidemiology of meningococci isolated in Niger in 2003 shows serogroup A sequence type (ST)-7 and serogroup W135 ST-11 or ST-2881 strains

In 2003, in the Zinder and Maradi regions (Niger), epidemics were due to serogroup A:4:P1.9 meningococci belonging to sequence type 7 (ST-7). In Niamey, only sporadic cases were reported: 55% of the meningococcus strains were in serogroup A, and 38% were in serogroup W135 and could be placed in ST-11, identical to the 2002 Burkina Faso epidemic clone, and in ST-2881, a new ST.

The establishment of Neisseria meningitidis serogroup W135 of the clonal complex ET-37/ST-11 as an epidemic clone and the persistence of serogroup A isolates in Burkina Faso

We analyzed 48 invasive isolates of Neisseria meningitidis that were isolated from meningitis cases in Burkina Faso (April 2002 to April 2003). Thirty-nine of these isolates had the phenotype (serogroup:serotype:serosubtype) W135:2a:P1.5,2, eight isolates were A:4:P1.9 and one isolate was nongroupable:nonserotypable:nonserosubtypable. Genotyping of meningococcal isolates showed that W135 isolates belonged to the sequence type (ST)-11. The nongroupable isolate was of genogroup W135 and belonged to ST-192. Isolates of serogroup A belonged to ST-2859 (a member of the subgroup III/ST-5 clonal complex). W135 (ST-11) isolates involved in meningitis outbreaks in Burkina Faso differed from those involved in the Hajj-2000 associated outbreak by their pulsed-field gel electrophoresis profile. These data confirm the changing epidemiology of meningococcal infection in Burkina Faso with the establishment and expansion of serogroup W135 N. meningitidis strains of the ET-37/ST-11 clonal complex, as well as the emergence of a new clone within the subgroup III/ST-5 clonal complex.

Interlaboratory comparison of PCR-based identification and genogrouping of Neisseria meningitidis

Twenty clinical samples (18 cerebrospinal fluid samples and 2 articular fluid samples) were sent to 11 meningococcus reference centers located in 11 different countries. Ten of these laboratories are participating in the EU-MenNet program (a European Union-funded program) and are members of the European Monitoring Group on Meningococci. The remaining laboratory was located in Burkina Faso. Neisseria meningitidis was sought by detecting several meningococcus-specific genes (crgA, ctrA, 16S rRNA, and porA). The PCR-based nonculture method for the detection of N. meningitidis gave similar results between participants with a mean sensitivity and specificity of 89.7 and 92.7%, respectively. Most of the laboratories also performed genogrouping assays (siaD and mynB/sacC). The performance of genogrouping was more variable between laboratories, with a mean sensitivity of 72.7%. Genogroup B gave the best correlation between participants, as all laboratories routinely perform this PCR. The results for genogroups A and W135 were less similar between the eight participating laboratories that performed these PCRs.

Molecular genetic methods in diagnosis and direct characterization of acute bacterial central nervous system infections

Acute bacterial infection of the central nervous system requires rapid and adequate management. Etiological diagnosis is hence crucial. Moreover, the epidemic threat of certain bacteria necessitates a reliable characterization of the involved bacterial strains to follow the spread of epidemic strains. Conventional identification and characterization of etiological agents are basically based on culture and identification of bacterial markers most frequently by serological assays. Molecular identification and characterization of bacteria have been employed. They provide more reliable analysis of bacterial isolates. Molecular methods for non-culture diagnosis of bacterial infections have recently been developed. In many cases, the molecular assays have decreased the identification time of positive cultures and rescued detection of pathogens in culture-negative clinical samples.

[Meningococcal disease diagnostic criteria in Greater Metropolitan Campinas, São Paulo State, Brazil]

The aim of this article is to evaluate confirmatory criteria: culture, latex agglutination, counter immunoelectrophoresis, microscopic examination, and clinical/epidemiological criteria for cases of meningococcal disease reported in Greater Metropolitan Campinas, São Paulo State, Brazil, from 1993 to 2002 (568 cases). The following variables were also studied: clinical features, gender, age, city, hospital, case fatality, seasonality, and Neisseria meningitidis serogroup. Culture as a confirmatory criterion was the dependent variable in univariate analysis. The mean proportion of confirmatory criterion by culture was 68.7%. Clinical features of meningococcal disease -- meningitis without septicemia (OR = 2.87; CI: 1.89-4.38) and septicemia without meningitis (OR = 0.26; CI: 0.17-0.45) -- were associated with confirmation by culture. Case fatality rates were different among all diagnostic criteria. More attention should be given to etiological diagnostic confirmation in more severe cases. Diagnostic methods such as PCR may improve etiological confirmation of meningococcal disease in cases with negative cultures.