Capsular switching in invasive Neisseria meningitidis, Brazil(1)

Genetic characterization of clonal complex sequence type 2057 (cc2057) serogroup B Neisseria meningitidis strains unique to Japan and identification of a capsular-switched serogroup Y isolate cc2057

Introduction. Only approximately 40 cases of invasive meningococcal diseases are reported annually in Japan, and the dominant strains are serogroup Y meningococci (MenY) followed by serogroup B meningococci (MenB). Within the last 10 years, Neisseria meningitidis strains belonging to clonal complex (cc)2057 have become dominant among Japanese MenB and have not been identified in countries other than Japan.Hypothesis/Gap Statement. The uniqueness of cc2057 N. meningitidis strains was considered to be epidemiologically of importance, and some genetic features could be hidden in the genome of cc2057 meningococci.Method. We investigated 22 cc2057 MenB and one cc2057 MenY using whole genome sequencing (WGS) and also predicted the potential coverage of 4CMenB and bivalent rLP2086 vaccines in silico.Results. cc2057 N. meningitidis strains were phylogenetically assigned to two clades. Three hypothetical genes homologous to those in Neisseria lactamica and sequences related to a new CRISPR Cas9 system were found only in the genome of cc2057 strains. Moreover, one cc2057 MenY strain was presumed to be capsular-switched at the capsule synthesis (cps) locus. The potential coverage of 4CMenB and rLP2086 for cc2057 MenB strains was estimated to be very low.Conclusion. To the best of our knowledge, this is the first study to provide genetic insights from epidemiologically unique N. meningitidis cc2057 strains isolated only in Japan, an island country.

Lung abscess due to Neisseria meningitidis serogroup X-unexpected virulence of a commensal resulting from putative serogroup B capsular switching

To report the first case of a lung abscess caused by Neisseria meningitidis (Nm) and to genetically characterize the rare underlying capsule switching event. The strain (PT NmX) was subjected to whole genome sequencing, and a comparative gene-by-gene analysis was performed based on 1605 N. meningitidis core loci that constitute the MLST core-genome scheme (cgMLST) V1.0. All ~ 9,600 genomes available on Neisseria PubMLST (until 30th November 2019) from all serogroups were used to better identify the genome make-up of the PT NmX strain. This strain was found to be highly divergent from other NmX reported worldwide and to belong to a new sequence type (ST-14273), with the finetype X: P1.19,15-1:F5-2. Moreover, it revealed a closer genetic proximity to strains from serogroup B than to other serogroups, suggesting a genome backbone associated with serogroup B, while it presents a capsule synthesis region derived from a NmX strain. We describe a new hybrid NmB/X isolate from a noninvasive meningococcal infection, causing lung abscess. Despite capsular switching events involving serogroup X are rare, it may lead to the emergence of pathogenic potential. Studies should continue to better understand the molecular basis underlying Neisseria strains' ability to spread to body compartments other than the tissues for which their tropism is already known.

Epidemics of meningococcal meningitis in Northern Nigeria focus on preventive measures

Throughout the past 200 years, epidemics of meningococcal infection have been noted in Northern Nigeria. Consequently, control of meningococcal meningitis is one of the major priorities in infection control in the region. The proportions of cases of invasive meningococcal disease (IMD) caused by the five common serotypes (A, B, C, Y, and W135) vary among different regions and within specific geographic locations. Hence, effective and comprehensive disease control can only be achieved with the use of vaccines that target all of these disease-causing serotypes. Vaccines for the majority of meningococcal serogroups implicated in causing IMD are available in developed countries and have proven effective in reducing the disease incidence. However, the overall success of a vaccine depends on its coverage of the at-risk population as well as safety and effectiveness of the vaccine at preventing disease. Therefore, maximizing the global impact of these vaccines requires having them made available in regions with the high incidence of the disease, like Northern Nigeria, where rates of meningococcal disease are several times higher than in industrialized nations, and the reported mortality is usually high.

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.

Capsule switching of Neisseria meningitidis sequence type 7 serogroup A to serogroup X

OBJECTIVES

The bacterial pathogen Neisseria meningitidis is able to escape the currently available capsule-based vaccines by undergoing capsule switching. In this study, we investigated whether capsule switching has occurred in a recently emerged sequence type (ST) 7 serogroup X isolate in China, for which currently no vaccine is available.

METHODS

To identify capsule switching breakpoints, the capsule locus and flanking regions of the ST-7 serogroup X isolate and three endemic ST-7 serogroup A isolates were sequenced and compared. To obtain further insight into capsule switching frequency and length of DNA fragments involved, capsule switching assays were performed using genomic DNA containing combinations of antibiotic selection markers at various locations in the capsule locus and flanking regions.

RESULTS

Sequence analyses showed that capsule switching has occurred and involved a 8450 bp serogroup X DNA fragment spanning the region from galE to ctrC. Capsule switching assays indicate that capsule switching occurs at a frequency of 6.3 × 10^-6 per bacterium per μg of DNA and predominantly involved DNA fragments of about 8.1-9.6 kb in length.

CONCLUSIONS

Our results show that capsule switching in N. meningitidis occurs at high frequency and involves recombination in the flanking regions of the capsule biosynthesis genes.

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.

Genomic Investigation Reveals Highly Conserved, Mosaic, Recombination Events Associated with Capsular Switching among Invasive Neisseria meningitidis Serogroup W Sequence Type (ST)-11 Strains

Neisseria meningitidis is an important cause of meningococcal disease globally. Sequence type (ST)-11 clonal complex (cc11) is a hypervirulent meningococcal lineage historically associated with serogroup C capsule and is believed to have acquired the W capsule through a C to W capsular switching event. We studied the sequence of capsule gene cluster (cps) and adjoining genomic regions of 524 invasive W cc11 strains isolated globally. We identified recombination breakpoints corresponding to two distinct recombination events within W cc11: A 8.4-kb recombinant region likely acquired from W cc22 including the sialic acid/glycosyl-transferase gene, csw resulted in a C→W change in capsular phenotype and a 13.7-kb recombinant segment likely acquired from Y cc23 lineage includes 4.5 kb of cps genes and 8.2 kb downstream of the cps cluster resulting in allelic changes in capsule translocation genes. A vast majority of W cc11 strains (497/524, 94.8%) retain both recombination events as evidenced by sharing identical or very closely related capsular allelic profiles. These data suggest that the W cc11 capsular switch involved two separate recombination events and that current global W cc11 meningococcal disease is caused by strains bearing this mosaic capsular switch.

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.

How the Knowledge of Interactions between Meningococcus and the Human Immune System Has Been Used to Prepare Effective Neisseria meningitidis Vaccines

In the last decades, tremendous advancement in dissecting the mechanisms of pathogenicity of Neisseria meningitidis at a molecular level has been achieved, exploiting converging approaches of different disciplines, ranging from pathology to microbiology, immunology, and omics sciences (such as genomics and proteomics). Here, we review the molecular biology of the infectious agent and, in particular, its interactions with the immune system, focusing on both the innate and the adaptive responses. Meningococci exploit different mechanisms and complex machineries in order to subvert the immune system and to avoid being killed. Capsular polysaccharide and lipooligosaccharide glycan composition, in particular, play a major role in circumventing immune response. The understanding of these mechanisms has opened new horizons in the field of vaccinology. Nowadays different licensed meningococcal vaccines are available and used: conjugate meningococcal C vaccines, tetravalent conjugate vaccines, an affordable conjugate vaccine against the N. menigitidis serogroup A, and universal vaccines based on multiple antigens each one with a different and peculiar function against meningococcal group B strains.

Three outbreak-causing Neisseria meningitidis serogroup C clones, Brazil(1.)

During 2003–2012, 8 clusters of meningococcal disease were identified in Rio de Janeiro State, Brazil, all caused by serogroup C Neisseria meningitidis. The isolates were assigned to 3 clonal complexes (cc): cc11, cc32, and cc103. These hyperinvasive disease lineages were associated with endemic disease, outbreaks, and high case-fatality rates.

Three outbreak-causing Neisseria meningitidis serogroup C clones, Brazil(1.)

During 2003-2012, 8 clusters of meningococcal disease were identified in Rio de Janeiro State, Brazil, all caused by serogroup C Neisseria meningitidis. The isolates were assigned to 3 clonal complexes (cc): cc11, cc32, and cc103. These hyperinvasive disease lineages were associated with endemic disease, outbreaks, and high case-fatality rates.

Controlling serogroup B invasive meningococcal disease: the Canadian perspective

With publically funded meningococcal immunization programs established in infants, children and adolescents, Canada is at the forefront of invasive meningococcal disease prevention. The advent of two new serogroup B vaccines that may protect against multiple disease-causing strains offers the potential to reduce endemic disease to very low levels in Canada. Canada likely will be one of the first countries with approval to use recombinant serogroup B vaccine. However, inclusion of these new vaccines into public immunization programs will be decided at the provincial/territorial level, rather than nationally, and may result initially in different immunization schedules throughout the country as we have seen with conjugate meningococcal vaccines. Such heterogeneous use and adoption of new vaccines complicates disease control, but may assist in evaluation of effectiveness. Minimally, it requires regionally specific information. In this article, the authors provide an overview of the Canadian epidemiology, serogroup B vaccine characteristics, potential strain coverage, immunization strategies and remaining postmarketing research questions.