Capsule switching among C:2b:P1.2,5 meningococcal epidemic strains after mass immunization campaign, Spain

Capsules and their traits shape phage susceptibility and plasmid conjugation efficiency

Bacterial evolution is affected by mobile genetic elements like phages and conjugative plasmids, offering new adaptive traits while incurring fitness costs. Their infection is affected by the bacterial capsule. Yet, its importance has been difficult to quantify because of the high diversity of confounding mechanisms in bacterial genomes such as anti-viral systems and surface receptor modifications. Swapping capsule loci between Klebsiella pneumoniae strains allowed us to quantify their impact on plasmid and phage infection independently of genetic background. Capsule swaps systematically invert phage susceptibility, revealing serotypes as key determinants of phage infection. Capsule types also influence conjugation efficiency in both donor and recipient cells, a mechanism shaped by capsule volume and conjugative pilus structure. Comparative genomics confirmed that more permissive serotypes in the lab correspond to the strains acquiring more conjugative plasmids in nature. The least capsule-sensitive pili (F-like) are the most frequent in the species' plasmids, and are the only ones associated with both antibiotic resistance and virulence factors, driving the convergence between virulence and antibiotics resistance in the population. These results show how traits of cellular envelopes define slow and fast lanes of infection by mobile genetic elements, with implications for population dynamics and horizontal gene transfer.

Neisseria meningitidis disease-associated clones in Amazonas State, Brazil

BACKGROUND

The aim of this study is to describe the molecular epidemiology of Neisseria meningitidis invasive disease before the introduction of serogroup C conjugate vaccine in Amazonas State in 2010.

METHODS

Meningococcal disease reported cases were investigated in Amazonas State during the period 2000-2010. N. meningitidis isolates (n = 196) recovered from patients were genotyped by multilocus sequence typing (MLST) and sequencing of porB, porA, fetA, fHbp and penA. Antimicrobial susceptibility was determined using E-test.

RESULTS

In the study period, 948 cases were reported; the incidence was 2.8 for the entire state and 4.8 per 100,000 in the capital of Manaus. Most meningococcal disease was caused by N. meningitidis belonging to ST-32 (72%; 141/196) or ST-103 (21%; 41/196) clonal complexes. Capsular switching (B→C) was suggested within clonal complex (cc) 32. There were 6 (3%; 6/196) strains with intermediate susceptibility to penicillin and a single strain was resistant to rifampicin. Since 2007, serogroup C strains belonging to the cc103 have predominated and case-fatality has increased.

CONCLUSION

We demonstrate a high rate of meningococcal disease in Amazonas State, where, like other parts of Brazil, serogroup C replaced serogroup B during 2000s. These data serve as a baseline to measure impact of serogroup C conjugate vaccine introduction in 2010. This study emphasizes the need for enhanced surveillance to monitor changes in meningococcal disease trends following the introduction of meningococcal vaccines.

Genetic Analysis of Neisseria meningitidis Sequence Type 7 Serogroup X Originating from Serogroup A

Neisseria meningitidis causes meningococcal disease, often resulting in fulminant meningitis, sepsis, and death. Vaccination programs have been developed to prevent infection of this pathogen, but serogroup replacement is a problem. Capsular switching has been an important survival mechanism for N. meningitidis, allowing the organism to evolve in the present vaccine era. However, related mechanisms have not been completely elucidated. Genetic analysis of capsular switching between diverse serogroups would help further our understanding of this pathogen. In this study, we analyzed the genetic characteristics of the sequence type 7 (ST-7) serogroup X strain that was predicted to arise from ST-7 serogroup A at the genomic level. By comparing the genomic structures and sequences, ST-7 serogroup X was closest to ST-7 serogroup A, whereas eight probable recombination regions, including the capsular gene locus, were identified. This indicated that serogroup X originated from serogroup A by recombination leading to capsular switching. The recombination involved approximately 8,540 bp from the end of the ctrC gene to the middle of the galE gene. There were more recombination regions and strain-specific single-nucleotide polymorphisms in serogroup X than in serogroup A genomes. However, no specific gene was found for each serogroup except those in the capsule gene locus.

Regulation of capsule in Neisseria meningitidis

Neisseria meningitidis, a devastating pathogen exclusive to humans, expresses capsular polysaccharides that are the major meningococcal virulence determinants and the basis for successful meningococcal vaccines. With rare exceptions, the expression of capsule (serogroups A, B, C, W, X, Y) is required for systemic invasive meningococcal disease. Changes in capsule expression or structure (e.g. hypo- or hyper-encapsulation, capsule "switching", acetylation) can influence immunologic diagnostic assays or lead to immune escape. The loss or down-regulation of capsule is also critical in meningococcal biology facilitating meningococcal attachment, microcolony formation and the carriage state at human mucosal surfaces. Encapsulated meningococci contain a cps locus with promoters located in an intergenic region between the biosynthesis and the conserved capsule transport operons. The cps intergenic region is transcriptionally regulated (and thus the amount of capsule expressed) by IS element insertion, by a two-component system, MisR/MisS and through sequence changes that result in post-transcriptional RNA thermoregulation. Reversible on-off phase variation of capsule expression is controlled by slipped strand mispairing of homo-polymeric tracts and by precise insertion and excision of IS elements (e.g. IS1301) in the biosynthesis operon. Capsule structure can be altered by phase-variable expression of capsular polymer modification enzymes or "switched" through transformation and homologous recombination of different polymerases. Understanding the complex regulation of meningococcal capsule has important implications for meningococcal biology, pathogenesis, diagnostics, current and future vaccine development and vaccine strategies.

Sequence Type 4821 Clonal Complex Serogroup B Neisseria meningitidis in China, 1978-2013

Serogroup B Neisseria meningitidis strains belonging to sequence type 4821 clonal complex (CC4821), a hyperinvasive lineage first identified for serogroup C in 2003, have been increasingly isolated in China. We characterized the outer membrane protein genes of 48 serogroup B and 214 serogroup C strains belonging to CC4821 and analyzed the genomic sequences of 22 strains. Four serogroup B strains had porin A (i.e., PorA), PorB, and ferric enterobactin transport (i.e., FetA) genotypes identical to those for serogroup C. Phylogenetic analysis of the genomic sequences showed that the 22 CC4821 strains from patients and healthy carriers were unevenly clustered into 2 closely related groups; each group contained serogroup B and C strains. Serogroup B strains appeared variable at the capsule locus, and several recombination events had occurred at uncertain breakpoints. These findings suggest that CC4821 serogroup C N. meningitidis is the probable origin of highly pathogenic CC4821 serogroup B strains.

The capsule polymerase CslB of Neisseria meningitidis serogroup L catalyzes the synthesis of a complex trimeric repeating unit comprising glycosidic and phosphodiester linkages

Neisseria meningitidis is a human pathogen causing bacterial meningitis and sepsis. The capsular polysaccharide surrounding N. meningitidis is a major virulence factor. The capsular polysaccharide consists of polyhexosamine phosphates in N. meningitidis serogroups A and X. The capsule polymerases (CPs) of these serogroups are members of the Stealth protein family comprising d-hexose-1-phosphate transferases from bacterial and protozoan pathogens. CslA, one of two putative CPs of the pathophysiologically less relevant N. meningitidis serogroup L, is one of the smallest known Stealth proteins and caught our attention for structure-function analyses. Because the N. meningitidis serogroup L capsule polymer consists of a trimeric repeating unit ([→3)-β-d-GlcNAc-(1→3)-β-d-GlcNAc-(1→3)-α-d-GlcNAc-(1→OPO3→]n), we speculated that the two predicted CPs (CslA and CslB) work together in polymer production. Consequently, both enzymes were cloned, overexpressed, and purified as recombinant proteins. Contrary to our expectation, enzymatic testing identified CslB to be sufficient to catalyze the synthesis of the complex trimeric N. meningitidis serogroup L capsule polymer repeating unit. No polymerase activity was detected for CslA, although the enzyme facilitated the hydrolysis of UDP-GlcNAc. Bioinformatics analyses identified two glycosyltransferase (GT) domains in CslB. The N-terminal domain modeled with 100% confidence onto a number of GT-A folded proteins, whereas the C-terminal domain modeled with 100% confidence onto TagF, a GT-B folded teichoic acid polymerase from Staphylococcus epidermidis. Amino acid positions known to have critical catalytic functions in the template proteins were conserved in CslB, and their point mutation abolished enzyme activity. CslB represents an enzyme of so far unique complexity regarding both the catalyzed reaction and enzyme architecture.

A decade of invasive meningococcal disease surveillance in Poland

Background

Neisseria meningitidis is a leading etiologic agent of severe invasive disease. The objective of the study was to characterise invasive meningococcal disease (IMD) epidemiology in Poland during the last decade, based on laboratory confirmed cases.

Methods

The study encompassed all invasive meningococci collected between 2002 and 2011 in the National Reference Centre for Bacterial Meningitis. The isolates were re-identified and characterised by susceptibility testing, MLST analysis, porA and fetA sequencing. A PCR technique was used for meningococcal identification directly from clinical materials.

Results

In the period studied, 1936 cases of IMD were confirmed, including 75.6% identified by culture. Seven IMD outbreaks, affecting mostly adolescents, were reported; all were caused by serogroup C meningococci of ST-11. The highest incidence was observed among children under one year of age (15.71/100,000 in 2011). The general case fatality rate in the years 2010–2011 was 10.0%. Meningococci of serogroup B, C, Y and W-135 were responsible for 48.8%, 36.6%, 1.2% and 1.2% of cases, respectively. All isolates were susceptible to third generation cephalosporins, chloramphenicol, ciprofloxacin, and 84.2% were susceptible to penicillin. MLST analysis (2009–2011) revealed that among serogroup B isolates the most represented were clonal complexes (CC) ST-32CC, ST-18CC, ST-41/44CC, ST-213CC and ST-269CC, and among serogroup C: ST-103CC, ST-41/44CC and ST-11CC.

Conclusions

The detection of IMD in Poland has changed over time, but observed increase in the incidence of the disease was mostly attributed to changes in the surveillance system including an expanded case definition and inclusion of data from non-culture diagnostics.

Phenotypic and genotypic characterization of meningococcal carriage and disease isolates in Burkina Faso after mass vaccination with a serogroup a conjugate vaccine

Background

The conjugate vaccine against serogroup A Neisseria meningitidis (NmA), MenAfriVac, was first introduced in mass vaccination campaigns of the 1-29-year-olds in Burkina Faso in 2010. The aim of this study was to genetically characterize meningococcal isolates circulating in Burkina Faso before and up to 13 months after MenAfriVac mass vaccination.

Methods

A total of 1,659 meningococcal carriage isolates were collected in a repeated cross-sectional carriage study of the 1-29-year-olds in three districts of Burkina Faso in 2010 and 2011, before and up to 13 months after mass vaccination. Forty-two invasive isolates were collected through the national surveillance in Burkina Faso in the same period. All the invasive isolates and 817 carriage isolates were characterized by serogroup, multilocus sequence typing and porA-fetA sequencing.

Results

Seven serogroup A isolates were identified, six in 2010, before vaccination (4 from carriers and 2 from patients), and one in 2011 from an unvaccinated patient; all were assigned to sequence type (ST)-2859 of the ST-5 clonal complex. No NmA carriage isolate and no ST-2859 isolate with another capsule were identified after vaccination. Serogroup X carriage and disease prevalence increased before vaccine introduction, due to the expansion of ST-181, which comprised 48.5% of all the characterized carriage isolates. The hypervirulent serogroup W ST-11 clone that was responsible for most of meningococcal disease in 2011 and 2012 was not observed in 2010; it appeared during the epidemic season of 2011, when it represented 40.6% of the serogroup W carriage isolates.

Conclusions

Successive clonal waves of ST-181 and ST-11 may explain the changing epidemiology in Burkina Faso after the virtual disappearance of NmA disease and carriage. No ST-2859 strain of any serogroup was found after vaccination, suggesting that capsule switching of ST-2859 did not occur, at least not during the first 13 months after vaccination.

Meningococcal disease: changes in epidemiology and prevention

The human bacterial pathogen Neisseria meningitidis remains a serious worldwide health threat, but progress is being made toward the control of meningococcal infections. This review summarizes current knowledge of the global epidemiology and the pathophysiology of meningococcal disease, as well as recent advances in prevention by new vaccines. Meningococcal disease patterns and incidence can vary dramatically, both geographically and over time in populations, influenced by differences in invasive meningococcal capsular serogroups and specific genotypes designated as ST clonal complexes. Serogroup A (ST-5, ST-7), B (ST-41/44, ST-32, ST-18, ST-269, ST-8, ST-35), C (ST-11), Y (ST-23, ST-167), W-135 (ST-11) and X (ST-181) meningococci currently cause almost all invasive disease. Serogroups B, C, and Y are responsible for the majority of cases in Europe, the Americas, and Oceania; serogroup A has been associated with the highest incidence (up to 1000 per 100,000 cases) and large outbreaks of meningococcal disease in sub-Saharan Africa and previously Asia; and serogroups W-135 and X have emerged to cause major disease outbreaks in sub-Saharan Africa. Significant declines in meningococcal disease have occurred in the last decade in many developed countries. In part, the decline is related to the introduction of new meningococcal vaccines. Serogroup C polysaccharide-protein conjugate vaccines were introduced over a decade ago, first in the UK in a mass vaccination campaign, and are now widely used; multivalent meningococcal conjugate vaccines containing serogroups A, C, W-135, and/or Y were first used for adolescents in the US in 2005 and have now expanded indications for infants and young children, and a new serogroup A conjugate vaccine has recently been introduced in sub-Saharan Africa. The effectiveness of these conjugate vaccines has been enhanced by the prevention of person-to-person transmission and herd immunity. In addition, progress has been made in serogroup B-specific vaccines based on conserved proteins and outer membrane vesicles. However, continued global surveillance is essential in understanding and predicting the dynamic changes in the epidemiology and biological basis of meningococcal disease and to influence the recommendations for current and future vaccines or other prevention strategies.

Neisseria meningitidis serogroup B lipooligosaccharide genotyping reveals high prevalence of L2 strains in Spain and unexpected relationship with factor H-binding protein expression

Neisseria meningitidis may be classified according to the lipooligosaccharide immunotype. We show that this classification can be achieved by PCR genotyping of the genes involved in the lipooligosaccharide inner-core biosynthesis, lpt3, lpt6, lgtG and lot3. Genotyping data correlated well (90-100%) with mass spectrometry data and was, therefore, applied to screen a random subset of recent N. meningitidis serogroup B isolates from Europe. Analysis of the proportion of the different lipooligosaccharide types highlighted the predominance of L3 strains. Surprisingly, high rates of L2 type strains were found in Spain (17%, versus 2.5% in Germany and 1.9% in the United Kingdom). Therefore, we also investigated further these Spanish L2 strains in an attempt to explain such prevalence despite the known sensitivity of L2 immunotype to complement. We explored the hypothesis that these strains express high amounts of factor H-binding protein (fHbp), but we found, on the contrary, that L2 strains express low or undetectable amounts of fHbp. Our findings suggest that, in addition to a genetic analysis, a multivalent approach may be necessary to estimate the effectiveness of a N. meningitidis serogroup B vaccine.

Potential capsule switching from serogroup Y to B: The characterization of three such Neisseria meningitidis isolates causing invasive meningococcal disease in Canada

Three group B Neisseria meningitidis isolates, recovered from meningococcal disease cases in Canada and typed as B:2c:P1.5, were characterized. Multilocus sequence typing showed that all three isolates were related because of an identical sequence type (ST) 573. Isolates typed as 2c:P1.5 are common in serogroup Y meningococci but rare in isolates from serogroups B or C. Although no serogroup Y isolates have been typed as ST-573, eight isolates showed five to six housekeeping gene alleles that were identical to that of ST-573. This suggested that the B:2c:P1.5 isolates may have originated from serogroup Y organisms, possibly by capsule switching.

[Current situation of the epidemiology of meningococcal disease]

Neisseria meningitidis, the etiological agent of all forms of meningococcal disease, is still a cause for concern among society in general and especially among health workers. Several of its antigens have been used in strain characterization, and some have served as the basis for the development of vaccines. In this sense, the best known are the capsular polysaccharide, which defines the serogroups, the outer membrane protein of class 2/3, used for serotype classification, and the class 1 porins, defining the serosubtype. During the last 30 years, most cases of meningococcal disease in Spain have been due to serogroup B strains, with the exception of 1996 and 1997, when serogroup C cases became the most frequent. The capsular polysaccharide has been successfully used in the development of conjugate vaccines highly effective against A, Y and W135 serogroups and particularly against serogroup C isolates. The development of a vaccine against serogroup B strains for routine immunization is still uncertain. However, the use of specific vaccines based on antigenic formulations of class 1 protein, to be applied in epidemic situations, is closer to becoming a reality. Because of the current absence of a universal vaccine against N. meningitidis, specific surveillance programs are required to evaluate the importance of recombination processes affecting capsular expression. This type of event could produce new strain variants able to avoid the immunological response generated after vaccination.

Antigenic diversity ofNeisseria meningitidisisolated in Taiwan between 1995 and 2002

The geographic distribution of N. meningitidis is diverse. Information on the antigenic variation of N. meningitidis is important for the development of an outer membrane protein-based vaccine. As a first step towards vaccine development, serological typing was performed to determine the antigenic properties of 127 invasive N. meningitidis isolates collected in Taiwan between 1995 and 2002. With 31.5% non-serotypeable and 32.3% non-serosubtypeable, the 127 isolates fell into 51 phenotypes, with W135:NT:P1.5,2:L3,7,9, Y:14P1.5,2, and B:1:NST:L3,7,9 being the 3 most prevalent. Among the 37 serogroup B isolates, 15 serosubtypes were found, with P1.5,2 and P1.12,13 being the most prevalent. The high diversity of Por A among serogroup B isolates circulating in Taiwan poses a great challenge for the development of a PorA-based vaccine. Because 85% of the serogroup B isolates had the L3,7,9 immunotype, inclusion of L3,7,9 lipooligosaccharides in a PorA-based vaccine may be a promising approach. In addition, based on the phenotypic characterization, we suggest that both serogroup B and W135 isolates were endemic and that serogroup A, C, and Y isolates were imported, which may reflect increased international travel.

Evidence for capsule switching between carried and disease-causing Neisseria meningitidis strains

Changing antigenic structure such as with capsule polysaccharide is a common strategy for bacterial pathogens to evade a host immune system. The recent emergence of an invasive W:2a:P1.7-2,4 sequence type 11 (ST-11) strain of Neisseria meningitidis in New Zealand, an uncommon serogroup/serotype in New Zealand disease cases, was investigated for its genetic origins. Molecular typing of 107 meningococcal isolates with similar serotyping characteristics was undertaken to determine genetic relationships. Results indicated that the W:2a:P1.7-2,4 strain had emerged via capsule switching from a group C strain (C:2a:P1.7-2,4). Neither the upstream nor downstream sites of recombination could be elucidated, but sequence analysis demonstrated that at least 45 kb of DNA was involved in the recombination, including the entire capsule gene cluster. The oatWY gene carried by the W:2a:P1.7-2,4 strain contained the insertion sequence element IS1301, one of five variants of oatWY found in group W135 strains belonging to the carriage-associated ST-22 clonal complex. This suggested that the origin of the capsule genes carried by the invasive W:2a:P1.7-2,4 strain is carriage associated. These results provide novel evidence for the long-standing dogma that disease-associated strains acquire antigenic structure from carriage-associated strains. Moreover, the capsule switch described here has arisen from the exchange of the entire capsule locus.

B:2a:p1.5 meningococcal strains likely arisen from capsular switching event still spreading in Spain

Eighteen clustered cases of meningococcal disease associated with B:2a:P1.5 strains doubled the annual incidence up to 4.3 x 10(5) in Navarra, Spain, in 2007. Eleven percent of cases were fatalities, and 74% of cases were individuals 10 to 24 years old. This is the third cluster associated with this strain in northern Spain since 2001.

Molecular surveillance of Neisseria meningitidis capsular switching in Portugal, 2002-2006

Neisseria meningitidis capsular switching has been reported in several countries. In order to establish the genetic relationship within group B and C strains expressing subtypes 2a or 2b, and to evaluate whether C to B capsular switching occurred in Portugal, 64 meningococci (56 serogroup C and 8 serogroup B) isolated from invasive meningococcal disease were typed using molecular methods. The studied phenotypes, 2b:P1.5,2 and 2a:P1.5-1,10-8, were the most frequent among serogroup C, but were uncommon among serogroup B strains. The multi-locus sequence typing (MLST) allelic profile and the pulsed-field gel electrophoresis (PFGE) fingerprints showed that seven serogroup B strains were genotypically identical to C strains, suggesting that capsular switching occurred. Active laboratory surveillance to find evidence of capsule switching is a now priority as MenC was introduced in the Portuguese vaccination schedule in January 2006.

Impact of meningococcal serogroup C conjugate vaccines on carriage and herd immunity

BACKGROUND

In 1999, meningococcal serogroup C conjugate (MCC) vaccines were introduced in the United Kingdom for those under 19 years of age. The impact of this intervention on asymptomatic carriage of meningococci was investigated to establish whether serogroup replacement or protection by herd immunity occurred.

METHODS

Multicenter surveys of carriage were conducted during vaccine introduction and on 2 successive years, resulting in a total of 48,309 samples, from which 8599 meningococci were isolated and characterized by genotyping and phenotyping.

RESULTS

A reduction in serogroup C carriage (rate ratio, 0.19) was observed that lasted at least 2 years with no evidence of serogroup replacement. Vaccine efficacy against carriage was 75%, and vaccination had a disproportionate impact on the carriage of sequence type (ST)-11 complex serogroup C meningococci that (rate ratio, 0.06); these meningococci also exhibited high rates of capsule expression.

CONCLUSIONS

The impact of vaccination with MCC vaccine on the prevalence of carriage of group C meningococci was consistent with herd immunity. The high impact on the carriage of ST-11 complex serogroup C could be attributed to high levels of capsule expression. High vaccine efficacy against disease in young children, who were not protected long-term by the schedule initially used, is attributed to the high vaccine efficacy against carriage in older age groups.

Workshop on vaccine pressure and Neisseria meningitidis, Annecy, France, 9-11 March 2005

A 3-day workshop, "Vaccine pressure and Neisseria meningitidis", was held in Annecy, France, 9-11 March 2005, to summarize the current state of knowledge regarding N. meningitidis capsule switching and vaccine pressure from capsular polysaccharide-based N. meningitidis vaccines, including conjugates. Main discussion topics were the host-bacteria relationship and N. meningitidis population, worldwide experience of meningococcal vaccination, and using existing experience to shape the future of meningococcal vaccination strategies. The workshop concluded that there is no current evidence to suggest that serogroup C conjugate vaccine pressure has resulted in meningococcal serogroup switching or replacement.

Clonal distribution of invasive Neisseria meningitidis serogroup C strains circulating from 1976 to 2005 in greater Sao Paulo, Brazil

Meningococcal disease is characterized by cyclic fluctuations in incidence, serogroup distribution, and antigenic profiles. In greater São Paulo, Brazil, there has been a constant increase in the incidence of serogroup C meningococcal disease since the late 1980s. To gain an understanding of changes in serogroup C meningococcal disease over three decades in greater São Paulo, Brazil, 1,059 invasive Neisseria meningitidis serogroup C isolates from 1976 and 2005 were analyzed. Three major clone complexes, sequence type (ST)-11, ST-8, and ST-103, were identified by multilocus sequence typing, and the isolates were characterized by serotyping and 16S rRNA typing. During the 30-year period, there were two major antigenic replacements: from 2a:P1.(5,2) to 2b:P1.3 and subsequently to 23:P1.14-6. All strains of clone ST-103 were characterized as serotype 23 and serosubtype P1.14-6. The origin of 23:P1.14-6 ST-103 complex strains is unknown, but efforts are needed to monitor its spread and define its virulence. The antigenic replacements we observed likely represent a mechanism to sustain meningococcal disease in the population as immunity to circulating strains accumulated.

Standardized nonculture techniques recommended for European reference laboratories

Culture-confirmed diagnosis of meningococcal invasive infections is often hindered by early antibiotic treatment. Nonculture molecular standardized methods are now essential tools for the immediate management of meningococcal infections. The European Monitoring Group on Meningococci (EMGM) recommends the following measures. (1) The implementation of standardized protocols of extraction methods for DNA isolation from clinical specimens for PCR-based identification and genogrouping of Neisseria meningitidis. (2) The use of molecular approaches (sequencing of target genes) for the determination of meningococcal susceptibility to antibiotics, such as sequencing of penA and rpoB genes for susceptibility to penicillin G and rifampicin, respectively. (3) The use of nonculture strain characterization by multilocus sequence typing (MLST) and sequence typing of porA and fetA. These approaches can be implemented either by individual reference laboratories or through collaboration and referral between centres.

A surveillance network for meningococcal disease in Europe

Between 1999 and 2004, the European Union Invasive Bacterial Infections Surveillance Network (EU-IBIS) received c. 50,000 reports of meningococcal disease from 27 participating countries. Analysis has demonstrated a major decline in the incidence of invasive disease in those countries that have introduced routine vaccination against serogroup C infection. The establishment of rapid reporting of W135 and B2a/B2b strains has been able to provide early reassurance that these strains are not emerging as major public health problems in Europe. Between September 2001 and February 2005, the EU-MenNet project offered further opportunities for enhancing this data resource. Collaborative projects included: improving the EU-IBIS website; reviewing case ascertainment in Europe; reviewing cost-effectiveness studies for meningococcal serogroup C conjugate (MCC) vaccination; international comparisons of MCC vaccine efficacy; and mathematical modelling studies. In addition, linking of data from the European Meningococcal Multi-locus Sequence Type Centre to epidemiological data was performed. Particular clonal complexes were found to be preferentially associated with certain serogroups. Case fatality was also found to vary with clonal complex, suggesting that genotype can be a marker for hypervirulence. The importance of close collaboration between networks of epidemiologists, microbiologists, and the wider scientific and public health community is demonstrated.

Characterisation of Neisseria meningitidis C:2b:P1.2,5 isolates in Poland

This study aimed to characterise Neisseria meningitidis C:2b:P1.2,5 isolates from Poland, which have now become predominant among serogroup C isolates in this country. Overall, 44 isolates (25 invasive and 19 from contact carriers) were typed by whole-cell ELISA and pulsed-field gel electrophoresis. Additionally, the invasive isolates were analysed by multilocus sequence typing, which revealed that they all belonged to the ST-8 complex/cluster A4. The emergence of this clone in other countries has resulted in mass immunisation campaigns and has been associated with a higher level of decreased susceptibility to penicillin; however the present study detected only one isolate that was penicillin-non-susceptible.

Multilocus sequence typing of Neisseria meningitidis directly from clinical samples and application of the method to the investigation of meningococcal disease case clusters

Infections associated with Neisseria meningitidis are a major public health problem in England, Wales, and Northern Ireland. Currently, over 40% of cases are confirmed directly from clinical specimens using PCR-based methodologies without an organism being isolated. A nested/seminested multilocus sequence typing (MLST) system was developed at the Health Protection Agency Meningococcal Reference Unit to allow strain characterization beyond the serogroup for cases confirmed by PCR only. This system was evaluated on a panel of 20 meningococcus-positive clinical specimens (3 cerebrospinal fluid and 17 blood samples) from different patients containing various concentrations of meningococcal DNA that had corresponding N. meningitidis isolates. In each case, the sequence type generated from the clinical specimens matched that produced from the corresponding N. meningitidis isolate; the sensitivity of the MLST system was determined to be less than 12 genome copies per PCR. The MLST system was then applied to 15 PCR meningococcus-positive specimens (2 cerebrospinal fluid and 13 blood samples), each from a different patient, involved in three case clusters (two serogroup B and one serogroup W135) for which no corresponding N. meningitidis organisms had been isolated. In each case, an MLST sequence type was generated, allowing the accurate assignment of individual cases within each of the case clusters. In summary, the adaptation of the N. meningitidis MLST to a sensitive nested/seminested format for strain characterization directly from clinical specimens provides an important tool for surveillance and management of meningococcal infection.

Antigenic and genetic characterization of serogroup C meningococci isolated from invasive meningococcal disease cases in Canada from 1999 to 2003

Four hundred and forty-two serogroup C Neisseria meningitidis isolates from individual invasive meningococcal disease (IMD) patients in Canada during the period 1999 to 2003 were analyzed. The majority (84%) of the serogroup C meningococci were characterized by the serotype antigen 2a and belonged to the clonal complex of electrophoretic type ET-15. However, after more than a decade of endemic disease as well as a number of outbreaks and many vaccination campaigns, both genetic and antigenic variants of the serogroup C serotype 2a meningococci were noted. Such variants include strains characterized as C:2a:P1.5 and C:2a:P1.7,1 as well as a non-serotypeable phenotype due to a mutational hot spot on the serotype 2a PorB outer-membrane protein. Meningococci characterized by the antigen formula B:2a:P1.5,2 and B:2a:P1.7,1 have also been found, which suggests capsule switching. Besides the clonal group of ET-15/ET-37, small numbers of serogroup C isolates were found to belong to the clonal complexes of ST-8 (Cluster A4), ST-41/44 (Lineage 3), ST-35, and ST-269.Key words: serogroup C, meningococci, genetic, antigenic, variants.

Meningococcal polysaccharide-protein conjugate vaccines

It is now 5 years since the UK became the first country to introduce the serogroup C meningococcal polysaccharide-protein conjugate vaccines (MenC) into its routine immunisation schedule. This article reviews the global use of MenC with particular reference to the range of immunisation strategies used internationally. To date, concerns that MenC may result in an increase in meningococcal disease due to non-C serogroups have not been realised. The vaccine has proved to be highly safe and effective; however, concerns have arisen regarding the duration of vaccine effectiveness. Although booster doses of MenC may potentially extend the duration of protection offered by the vaccine, there are, as yet, no studies assessing this option. Clinical trials are underway to assess new combination conjugate vaccines (containing A, C, Y, and W polysaccharides), and it is probable that these more broadly protective vaccines will become available in the near future.

Genetic lineages and their traits in Neisseria meningitidis

Neisseria meningitidis is a model organism for the study of bacterial population biology, for genome sequencing and pathogenicity research. In the recent years, our group has identified a variety of markers for hypervirulent lineages of meningococci, which in part could be validated for typing purposes. Furthermore, carrier strain collections of meningococci and N. lactamica were studied by multilocus sequence typing, and elucidated the impressive genetic variability of those species. Characterisation of meningococcal carrier strains allowed to define the capsule null locus (cnl) of meningococci, which frequently occurs among carrier isolates and renders strains constitutively unencapsulated. This finding poses the question about the yet unclear role of the meningococcal polysaccharide capsule in transmission and carriage. O-acetylation of the meningococcal polysaccharides is another variably expressed trait in meningococci. We identified the genes responsible for O-acetylation of the serogroup C, W-135 and Y capsules, and provided the genetic basis for understanding the variability of O-acetylation patterns in meningococci. The oatC and oatWY genes proved to be the first genes identified to be responsible for O-acetylation of polysialic acid.

An outbreak of serogroup C meningococcal disease in the province of Antwerp (Belgium) in 2001-2002

In 2001 an outbreak of Neisseria menigitidis serogroup C occurred in the province of Antwerp (Belgium). Over a year the incidence rate of meningococcal disease (MD) increased from 3.9 per 100,000 to 9.1 per 100,000 with a shift from serogroup B (87%) in 2000 to serogroup C (66%) in 2001. The most prominent phenotype was C:2a:P1.2,5. The incidence rate for serogroup C MD increased from 0.4 per 100,000 to 4.5 per 100,000 in 2001. The case fatality rate was 6.7% in 2001. After the introduction of a mass vaccination campaign with a conjugated vaccine against serogroup C MD the incidence of serogroup C MD fell from 4.5 to 1.8 per 100,000. As a result of the analysis of this outbreak, it was proposed to offer a vaccine against serogroup C to all people under 19 years of age. Part of this plan has been implemented to date in Belgium.

First report of capsule replacement among electrophoretic type 37 Neisseria meningitidis strains in Italy

This report describes the C-to-B capsular switching in four Neisseria meningitidis strains belonging to the electrophoretic type 37 (ET-37) complex. In particular, one strain belonged to the new sequence type 1860, which was first detected in the year 2000 in Italy and is now frequently isolated. The presence of switched serogroup B strains deserves special attention if they prove as able to spread as their serogroup C progenitors belonging to the hypervirulent ET-37 complex.