Pierre Nicolas

Meningococcal Meningitis: Unprecedented Incidence of Serogroup X—Related Cases in 2006 in Niger

BACKGROUNDnIn 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.nnnMETHODSnMeningitis 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.nnnRESULTSnFrom 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.nnnCONCLUSIONSnThis 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.

Fit genotypes and escape variants of subgroup III Neisseria meningitidis during three pandemics of epidemic meningitis

The genetic variability at six polymorphic loci was examined within a global collection of 502 isolates of subgroup III, serogroup A Neisseria meningitidis. Nine “genoclouds” were identified, consisting of genotypes that were isolated repeatedly plus 48 descendent genotypes that were isolated rarely. These genoclouds have caused three pandemic waves of disease since the mid-1960s, the most recent of which was imported from East Asia to Europe and Africa in the mid-1990s. Many of the genotypes are escape variants, resulting from positive selection that we attribute to herd immunity. Despite positive selection, most escape variants are less fit than their parents and are lost because of competition and bottlenecks during spread from country to country. Competition between fit genotypes results in dramatic changes in population composition over short time periods.

Molecular Epidemiology of Neisseria meningitidis Isolated in the African Meningitis Belt between 1988 and 2003 Shows Dominance of Sequence Type 5 (ST-5) and ST-11 Complexes

ABSTRACT At the two World Health Organization Collaborating Centers for Reference and Research on Meningococci in Marseilles, France, and Oslo, Norway, the multilocus sequence typing technique was used for the characterization of a total of 357 strains of meningococci isolated from meningitis cases in 13 African countries of the meningitis belt between 1988 and 2003. Among these strains, 278 of 357 (77.9%) belonged to the sequence type 5 (ST-5) complex; 23.2% were ST-5 and 53.5% were ST-7. ST-5 was probably introduced in Africa in 1987 and was responsible for most of the meningitis cases between 1988 and 2001. ST-7 emerged in the mid-1990s and has totally replaced ST-5 since 2002. These two STs characterized serogroup A strains and have been responsible for hundreds of thousands of cases. Fifty-two strains (14.3%) belonged to the ST-11 complex. The ST-11 complex was characterized by serogroup W135, which has been responsible for an increasing number of sporadic cases since 2000 and the first W135 epidemic ever seen in Africa (in Burkina Faso in 2002). Identification of W135 ST-11 strains in many countries is a great concern for the region. Apart from these two major clonal complexes, a few other clones, such as ST-2881, ST-181, and ST-751, were sporadically detected. Careful surveys for these clones need to be conducted, but at present they play only a minor role in the overall epidemiology of meningococcal meningitis.

Molecular strategies in biological evolution of antimicrobial peptides

Gene-encoded antimicrobial peptides that protect the skin of hylid and ranin frogs against noxious microorganisms are processed from a unique family of precursor polypeptides with a unique pattern of conserved and variable regions opposite to that of conventional secreted peptides. Precursors belonging to this family, designated the preprodermaseptin, have a common N-terminal preproregion that is remarkably well conserved both within and between species, but a hypervariable C-terminal domain corresponding to antimicrobial peptides with very different lengths, sequences, charges and antimicrobial spectra. Each frog species has its own distinct panoply of 10-20 antimicrobial peptides so that the 5000 species of ranids and hylids may produce approximately 100,000 different peptide antibiotics. The strategy that these frogs have evolved to generate this enormous array of peptides includes repeated duplications of a 150 million years old ancestral gene, focal hypermutation of the antimicrobial peptide domain maybe involving a mutagenic DNA polymerase similar to Escherichia coli Pol V, and subsequent actions of positive (diversifying) selection. The hyperdivergence of skin antimicrobial peptides can be viewed as the successful evolution of a multi-drug defense system that provides frogs with maximum protection against rapidly changing microbial biota and minimizes the chance of microorganisms developing resistance to individual peptides. The impressive variations in the expression of frog skin antimicrobial peptides may be exploited for discovering new molecules and structural motifs targeting specific microorganisms for which the therapeutic armamentarium is scarce.

The Rise and Fall of Epidemic Neisseria meningitidis Serogroup W135 Meningitis in Burkina Faso, 2002–2005

BACKGROUNDnDuring the period 2001-2002, Burkina Faso reported its first meningitis epidemic due to Neisseria meningitidis (Nm) serogroup W135, prompting concerns that this serogroup would persist as a cause of epidemic disease.nnnMETHODSnDuring the period 2002-2005, hospital- and population-based surveillances were conducted in 3 districts in Burkina Faso. Etiology was determined by culture, polymerase chain reaction (PCR), and latex agglutination. Reference laboratories determined phenotype and genotype.nnnRESULTSnOf 2004 subjects who received a lumbar puncture, 265 were identified as having Nm, including 93 who had Nm serogroup A (NmA) and 146 who had Nm serogroup W135 (NmW135). Over the study period, the proportion of cases due to NmW135 decreased by >75%, primarily because of decreased occurrence among young children and in a single district. During peak epidemic months, the annualized incidence of NmW135 decreased from 146 cases to <1 case per 100,000 population. All but 2 NmW135 isolates were phenotype W135:2a:P1.5,2 (sequence type [ST]-11 clonal complex). All NmA isolates were phenotype A:4:P1-9 (ST-2859 of the ST-5 clonal complex). We identified 1 isolate from serogroup Y (ST-11 clonal complex), 1 isolate from serogroup X that was similar to strains previously associated with epidemic disease, and 1 isolate from serogroup W135 of the newly described ST-4375 complex.nnnCONCLUSIONSnFor unknown reasons, serogroup W135 achieved epidemic status, primarily among young children, and then largely disappeared over a short time period. The continued circulation of multiple strains with epidemic potential emphasizes the need for ongoing surveillance and the potential benefit of vaccines that are protective across serogroups.

Three Cases of Invasive Meningococcal Disease Caused by a Capsule Null Locus Strain Circulating among Healthy Carriers in Burkina Faso

During reinforced surveillance of acute bacterial meningitis in Burkina Faso, meningococcal strains of phenotype NG:NT:NST were isolated from cerebrospinal fluid samples from 3 patients. The strains were negative for the ctrA gene but were positive for the crgA gene. Molecular typing revealed that the strains harbored the capsule null locus (cnl) and belonged to the multilocus sequence type (ST)-192. PorA sequencing showed that all strains were either P1.18-11,42; P1.18,42-1; P1.18-11,42-1; P1.18-11,42-3; or P1.18-12,42-1. Sequencing also showed that all strains were negative for the FetA receptor gene. Serum killing assays showed these strains to be resistant, with the resistance comparable with that of a fully capsular serogroup B strain, MC58. The same strains were found in 14 healthy carriers in the general population of Bobo-Dioulasso (100% of ST-192 isolates tested for cnl). The presence of cnl meningococci that can escape serum killing and cause invasive disease is of concern for future vaccination strategies and should promote rigorous surveillance of cnl meningococcal disease.

Interlaboratory comparison of agar dilution and etest methods for determining the MICs of antibiotics used in management of Neisseria meningitidis infections

ABSTRACT Previous studies have shown that there is considerable variation in the methods and media used to determine the susceptibility of Neisseria meningitidis to antimicrobial agents in different countries. In this study, national and regional reference laboratories used a standardized methodology to determine the MICs of antibiotics used in the management of meningococcal infection. Fourteen laboratories participated in the study, determining the susceptibility to penicillin G, rifampin, cefotaxime, ceftriaxone, ciprofloxacin, and ofloxacin of a collection of 17 meningococci, of which 11 strains were previously defined as having intermediate resistance to penicillin (PenI) by sequencing and restriction fragment length polymorphism analysis of the penA gene. The MIC was determined by agar dilution and Etest with Mueller-Hinton agar (MH), MH supplemented with sheep blood (MH+B), and MH supplemented with heated (chocolated) blood. Several laboratories encountered problems obtaining confluent growth with unsupplemented MH. MH+B was considered to give the most congruent and reproducible results among the study laboratories. The modal MIC for MH+B for each antibiotic and method was calculated to define the MIC consensus, allowing assessment of each individual laboratorys data in relation to the others. The agreement in each antibiotic/method/medium combination was defined as the percentage of laboratories with a result within one dilution of the modal result. For the whole study, an agreement of 90.6% was observed between agar dilution and Etest methods. The agreement in each laboratory/antibiotic/method combination ranged from 98.2% to 69.7%, with six laboratories demonstrating agreement higher than 90% and 11 more than 80%. The ability of the laboratories to detect the PenI isolates ranged from 18.2% to 100%. The apparent difficulty in interpreting susceptibility to rifampin, particularly with the Etest method, is very interesting.

Differential contribution of C-terminal regions of dermorphin and dermenkephalin to opioid-sites selection and binding potency

Dermorphin and dermenkephalin are D-aminoacid containing peptides generated from processing of the plurifonctional biosynthetic precursor pro-dermorphin. Dermorphin, Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2 (DRM) and dermenkephalin, Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2 (DREK), are among the most selective and potent agonists described respectively for the mu- and delta-opioid receptors. In order to identify determinants of selectivity and high-affinity receptor binding of dermorphin and dermenkephalin, a series of analogs was investigated for their affinity at the mu- and delta-receptors in the brain. The tetrapeptide amino end of both DRM and DREK were found to display high affinity and selectivity towards mu-receptors. Substitution of the C-terminal tripeptide of DREK with that of DRM reversed the receptor selectivity of DREK from delta to mu. Replacement of the C-terminal tripeptide of DRM with the C-terminal counterpart of DREK shifted the selectivity of DRM from mu to delta. These data emphasize the critical contribution of the carboxy end of DREK to delta-selectivity. They further suggest that the potent mu-address lying in the N terminus of DREK is overwhelmed by the powerful delta-directing ability of the carboxy end. Unlike DREK, the C-terminus of DRM is not involved in opioid receptor sites selection but is important insofar as it serves to stabilize interactions of DRM with the mu-receptor binding site.

Recent increase in meningitis caused by Neisseria meningitidis serogroups A and W135 Yaoundé Cameroon.

From 1991 to 1998, Neisseria meningitidis serogroups A, B, and C represented 2%-10% of strains isolated from cases of bacterial meningitis in Yaoundé. During 1999 to 2000, the percentage of meningococci reached 17%, a proportion never reported since recordkeeping began in 1984. The increase of serogroup A meningococci and the emergence of W135 strains highlight the need for increased surveillance for better diagnosis and prevention.

Increase in Neisseria meningitidis Serogroup W135, Niger, 2010

To the Editor: Meningococcal epidemics in the African meningitis belt are generally caused by Neisseria meningitidis serogroup A strains, but they also can be caused by serogroup W135 or X strains. The largest reported outbreak caused by serogroup W135 occurred in Burkina Faso in 2002 with ≈13,000 suspected cases (1). Sporadic cases of meningitis caused by serogroup W135 have, however, been detected previously, notably in Niger since the early 1980s (2). This serogroup has also been associated with outbreaks in pilgrims to Mecca, Saudi Arabia, in 2000, and several clusters of cases occurred worldwide before 2002 (3). After 2003, no major outbreak caused by serogroup W135 was detected in sub-Saharan countries, only sporadic cases. Although Niger borders Burkina Faso, Niger has not experienced a large outbreak of meningitis caused by serogroup W135, with the exception of 7,906 suspected cases and 595 deaths declared in 2001; serogroup W135 represented 12 (38.7%) of the small number (n = 31) of confirmed cases (4). In 2010, serogroup W135 may have caused a major outbreak (a large proportion of this serogroup was detected during the first 12 weeks). Niger residents have not been in contact with this serogroup in recent years and have never been immunized with the trivalent polysaccharide vaccine (A/C/W135). n nFrom January 1 through March 28, 2010, the Ministry of Public Health of the Republic of Niger reported 1,188 suspected cases of meningococcal disease, including 103 deaths (case-fatality rate 8.7%). Suspected cases were reported from all 8 provinces but predominantly in the provinces of Maradi (40%) and Tillabery (24%). At week 12, the districts of Maradi Commune and neighboring Madarounfa crossed the alert, or epidemic, threshold with cumulated attack rates per 100,000 inhabitants of 57.0 and 48.5, respectively. Zinder City district also crossed the alert threshold. n nLaboratory confirmation and microbiologic surveillance of meningococcal meningitis is conducted by the Centre de Recherche Medicale et Sanitaire by using culture or PCR (5) techniques on cerebrospinal fluid (CSF) or CSF-inoculated trans-isolates. During the study period, the Centre received 816 CSF or trans-isolate specimens (from 69% of the notified cases). Culture (n = 23, 2.8%) and PCR (all specimens) identified N. meningitidis as the predominant pathogen (n = 248, 30.4%), followed by Streptococcus pneumoniae (n = 35, 4.3%) and Haemophilus influenzae (n = 13, 1.6%). Among the 248 cases with confirmed meningococcal etiology, the most frequent serogroup was W135 (n = 121, 48.8%), followed by A (n = 116, 46.8%) and X (n = 2), indicating that serogroup W135 had increased markedly compared with the past 2 years (Figure). Among the 816 CSF specimens, 454 (56%) remained negative when tested for the presence of N. meningitidis, S. pneumoniae, or H. influenzae by PCR. Eighty-four (69.4%) of the serogroup W135 strains originated from the province of Maradi (southern Niger) and, more specifically, 36%.4% (n = 44) and 19.8% (n = 24) originated from the Madarounfa and Maradi districts, respectively. In contrast, serogroup A was mainly present in Tillabery (western Niger) with 49.1% (n = 57) of the strains and, to a lesser extent, in the provinces of Maradi (16.4%, n = 19) and Dosso (13.8%, n = 16). All meningococcal strains (n = 9 for W135, n = 1 for A) recovered from trans-isolates and analyzed by Etest (AB bioMerieux, Marcy l’Etoile, France) were susceptible to beta-lactams (penicillin, amoxicillin, and ceftriaxone), chloramphenicol, and rifampin. This finding supports the appropriateness of World Health Organization recommendations for antimicrobial drug treatment. The A strain belonged to the sequence type (ST) 7 and the W135 strains to ST 11, the same ST of the strain associated with outbreaks in pilgrims in Saudi Arabia in 2000 (3) and the strain that caused the large epidemic in Burkina Faso in 2002 (1). n n n nFigure n nEpidemic curve of cumulative confirmed cases of Neisseria meninigitidis serogroup W135 infections, Niger, 2008, 2009, and 2010 (weeks 1–12). No cases were found in 2008. n n n nThe mean ages of patients with confirmed cases of infection with serogroup W135 and serogroup A were 8.1 (SD 8.5) and 10.9 (SD 7.9) years, respectively. Although no significant difference was found in the mean ages, the age group was 1–4 years of age had more disease caused by serogroup W135, and children 5–14 years of age were most affected by serogroup A. Similarly, the attack rate during the outbreak of meningitis caused by serogroup W135 in Burkina Faso in 2002 was highest in patients <5 years of age, and the attack rate decreased as patients’ ages increased (6). n nReactive vaccination campaigns in some communes of Madarounfa district that had reached the epidemic threshold were launched by the Ministry of Public Health with a remaining 2009 stockpile (16,527 doses, 35.7% coverage) of the quadrivalent polysaccharide vaccine (A/C/Y/W135) from Medecins sans Frontieres. The International Coordinating Group on Vaccine Provision for Epidemic Meningitis Control has also recently approved the release of 381,526 doses of trivalent polysaccharide vaccine (A/C/W135) for vaccination campaigns in Maradi and Zinder districts. Future immunization campaigns will be implemented by Ministry of Public Health with the support of the World Health Organization and partners, including Medecins sans Frontieres and The United Nations Children’s Fund. n nGiven the large population at risk, and the low availability and high cost of the trivalent vaccine, a sound vaccination strategy is of particular importance to mitigate the expansion of serogroup W135 in the country. Microbiologic surveillance is critical in the early and accurate detection of meningococcal serogroups for determining the appropriate vaccine.