Population genetics and molecular epidemiology ofNeisseria meningitidis

Genomic characterization of invasive meningococcal X isolates from Brazil, 1992-2022

INTRODUCTION

Invasive meningococcal disease (IMD) is a major health problem. Given the post-COVID-19 pandemic scenario with the loosening of the non-pharmacological measures to control the virus transmission and considering the observed global reduction of meningococcal vaccination coverage, an increase in IMD cases can be expected.

METHODOLOGY

Using whole-genome sequencing, we characterized six Neisseria meningitidis serogroup X (MenX) isolates recovered from IMD cases in Brazil in the last 30 years.

RESULTS

The predominance (66.6%, 4/6) of ST2888 presenting fHbp 160, NHBA 129, NadA 21, and PorA 19,15 was found on isolates. Two novel STs, 15458 and 15477, were described.

CONCLUSION

This study describes the circulation of MenX lineage ST2888 in Brazil, previously reported only in Europe. Continuous universal surveillance is crucial to implement prompt public health measures aiming to prevent and control non-vaccine preventable serogroup X IMD cases.

Oropharyngeal meningococcal carriage in children and adolescents, a single center study in Buenos Aires, Argentina

Background

Neisseria meningitidis (Nm) pharyngeal carriage is a necessary condition for invasive disease. We present the first carriage study in children in Buenos Aires, Argentina, considering 2017 as a transition year. Aims: to assess the rate of Nm carriage, to determine genogroup, clonal complex and outer membrane protein distribution, to determine carriage risk factors by age.

Methods

Cross-sectional study including children 1–17 yrs, at Ricardo Gutiérrez Children’s Hospital in Buenos Aires 2017. Oro-pharyngeal swabs were taken and cultured within a short time after collection. Genogroup was determined by PCR and clonal complex by MLST. Categorical variables were analyzed.

Results

A total of 1,751 children were included. Group 1: 943 children 1–9 yrs, 38 Nm were isolated; overall carriage 4.0%. Genogroup distribution: B 26.3%, W 5.3%, Y 2.6%, Z 5.3%, other groups 7.9% and capsule null (cnl) 52.6%. Participating in extracurricular activities was the only independent predictor of Nm carriage. Group 2: 808 children 10–17 yrs, 76 Nm were isolated; overall carriage 9.4%. Genogroup distribution: B 19.7%, C 5.3%, W 7.9%, Y 9.2%, Z 5.3%, other groups 7.9% and cnl 44.7%. Independent predictors of carriage: attending pubs/night clubs and passive smoking (adjusted OR: 0.55, 95%CI = 0.32–0.93; p = 0.025).

Conclusions

Overall carriage was higher in 10–17 yrs. The isolates presenting the cnl locus were prevalent in both age groups and genogroup B was the second most frequent.

A Narrative Review of the Molecular Epidemiology and Laboratory Surveillance of Vaccine Preventable Bacterial Meningitis Agents: Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae and Streptococcus agalactiae

This narrative review describes the public health importance of four most common bacterial meningitis agents, Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, and S. agalactiae (group B Streptococcus). Three of them are strict human pathogens that normally colonize the nasopharynx and may invade the blood stream to cause systemic infections and meningitis. S. agalactiae colonizes the genito-gastrointestinal tract and is an important meningitis agent in newborns, but also causes invasive infections in infants or adults. These four bacteria have polysaccharide capsules that protect them against the host complement defense. Currently licensed conjugate vaccines (against S. pneumoniae, H. influenza, and N. meningitidis only but not S. agalactiae) can induce protective serum antibodies in infants as young as two months old offering protection to the most vulnerable groups, and the ability to eliminate carriage of homologous serotype strains in vaccinated subjects lending further protection to those not vaccinated through herd immunity. However, the serotype-specific nature of these vaccines have driven the bacteria to adapt by mechanisms that affect the capsule antigens through either capsule switching or capsule replacement in addition to the possibility of unmasking of strains or serotypes not covered by the vaccines. The post-vaccine molecular epidemiology of vaccine-preventable bacterial meningitis is discussed based on findings obtained with newer genomic laboratory surveillance methods.

Genomic surveillance of Neisseria meningitidis serogroup B invasive strains: Diversity of vaccine antigen types, Brazil, 2016-2018

Background

Neisseria meningitidis serogroup B remains a prominent cause of invasive meningococcal disease (IMD) in Brazil. Because two novel protein-based vaccines against serogroup B are available, the main purpose of this study was to provide data on the diversity and distribution of meningococcal vaccine antigen types circulating in Brazil.

Methodology

Genetic lineages, vaccine antigen types, and allele types of antimicrobial-associated resistance genes based on whole-genome sequencing of a collection of 145 Neisseria meningitidis serogroup B invasive strains recovered in Brazil from 2016 to 2018 were collected.

Results

A total of 11 clonal complexes (ccs) were identified among the 145 isolates, four of which were predominant, namely, cc461, cc35, cc32, and cc213, accounting for 72.0% of isolates. The most prevalent fHbp peptides were 24 (subfamily A/variant 2), 47 (subfamily A/variant 3), 1 (subfamily B/variant 1) and 45 (subfamily A/variant 3), which were predominantly associated with cc35, cc461, cc32, and cc213, respectively. The NadA peptide was detected in only 26.2% of the isolates. The most frequent NadA peptide 1 was found almost exclusively in cc32. We found seven NHBA peptides that accounted for 74.5% of isolates, and the newly described peptide 1390 was the most prevalent peptide exclusively associated with cc461. Mutated penA alleles were detected in 56.5% of the isolates, whereas no rpoB and gyrA mutant alleles were found.

Conclusion

During the study period, changes in the clonal structure of circulating strains were observed, without a predominance of a single hyperinvasive lineage, indicating that an epidemiologic shift has occurred that led to a diversity of vaccine antigen types in recent years in Brazil.

Characterization of invasive Neisseria meningitidis isolates recovered from children in Turkey during a period of increased serogroup B disease, 2013-2017

Diverse Neisseria meningitidis strains belonging to various serogroups and clonal complexes cause epidemic and endemic life-threatening disease worldwide. This study aimed to investigate the genetic diversity of recent invasive meningococci in Turkey with respect to multilocus sequence type (MLST) and also meningococcal serogroup B (MenB) vaccine antigens to enable assessment of potential MenB strain coverage using the genetic Meningococcal Antigen Typing System (gMATS). Fifty-four isolates, representing 37.5% of all pediatric (ages 0-18 years) invasive meningococcal disease cases in Turkey from January 2013 to December 2017, underwent genome sequence analysis. Thirty-six (66.7%) isolates were MenB, 10 (18.5%) were serogroup W (MenW), 4 (7.4%) were serogroup A (MenA), 3 (5.6%) were serogroup Y (MenY) and 1 (1.8%) was serogroup X (MenX). The MenB isolates were diverse with cc35 (19.4%), cc41/44 (19.4%) and cc32 (13.8%) as the most prevalent clonal complexes. The MenW isolates (n = 10) comprised cc11 (n = 5), ST-2754 (cc-unassigned; n = 4) and cc22 (n = 1). gMATS was indicative of high 4CMenB coverage (72.2-79.1%) of Turkish invasive MenB strains from pediatric patients. Strain coverage of several clonal complexes differed from that seen elsewhere in Europe highlighting the importance of performing local assessments and also the use of phenotypic methods, i.e. MATS, where possible. All of the isolates possessed in-frame fhbp alleles and so were potentially covered by MenB-fHbp. Continued surveillance is essential to guide recommendations for current and future vaccines as well as understanding changes in epidemiology.

WGS analysis of a penicillin-resistant Neisseria meningitidis strain containing a chromosomal ROB-1 β-lactamase gene

Objectives

Neisseria meningitidis is rarely penicillin resistant. We describe WGS analysis of a penicillin-resistant N. meningitidis collected from a case of invasive meningococcal disease.

Methods

Serogrouping, serotyping and serosubtyping were performed with specific antibodies. β-Lactamase was detected by nitrocefin. MICs were determined by Etest and agar dilution. Sequencing of N. meningitidis genomes was done on the Illumina MiSeq platform and genome data were analysed using the Bacterial Isolate Genome Sequence Database (BIGSdb) on the PubMLST Neisseria website (https://pubmlst.org/neisseria/). Transformation was used to confirm the genetic basis of the penicillin resistance.

Results

An N. meningitidis blood isolate from a female patient in her mid-50s with a painful and septic left shoulder was found to have penicillin MIC values of 3–12 mg/L. The isolate was typed as Y: 14, 19: P1.– and ST3587, and was weakly β-lactamase positive. WGS analysis identified a full-length copy of the β-lactamase gene bla_ROB-1, which was contained on a 1719 bp insert with a G + C content of 41.7% (versus a G + C content of N. meningitidis of 51.7%), suggesting that the bla_ROB-1 gene came from a different bacterial species. A GenBank analysis of the bla_ROB-1 gene insert found 99.77% identity with a DNA segment found in plasmid pB1000′ from Haemophilus influenzae. Transformation of a penicillin-susceptible strain with the bla_ROB-1 gene conferred β-lactamase activity and penicillin resistance.

Conclusions

N. meningitidis serogroup Y, ST3587 can carry and express the bla_ROB-1 gene, leading to penicillin resistance. It is highly likely that the N. meningitidis isolate acquired the bla_ROB-1 gene from H. influenzae.

Enterotoxin gene profile and molecular epidemiology of Aeromonas species from fish and diverse water sources

AIMS

This investigation was undertaken to study the prevalence, enterotoxin gene profile and molecular epidemiology of Aeromonads from various sources of water (182) and fish (173).

METHODS AND RESULTS

A total of 116 Aeromonas sp. were isolated, of which 48 (26·37%) were from water and 68 (34·62%) were from fish samples collected from retail markets and fish farms. The Aeromonads were recovered from all types of water sources viz. drinking water (13%), surface waters (26%) and fish ponds (69%). The most prevalent species recovered from drinking water was A. hydrophila, from fish ponds it was A. caviae, from surface water sources A. hydrophila and A. caviae were recovered more frequently, and A. hydrophila and A. veronii bv. sobria were isolated predominantly from gills of fish samples. On multiplex PCR analysis for the detection of enterotoxin genes (act, alt, ast), the above mentioned Aeromonas species frequently contained enterotoxin genes, irrespective of their sources. From isolates across all the sources, act (63%) and alt (57%) genes were encountered more frequently than ast (6%). The enterobacterial repetitive intergenic consensus sequences polymerase chain reaction was used for typing of isolates and most of the isolates from water and fish were related, owing to similar ecosystem.

CONCLUSION

A wide distribution of enterotoxin genes in Aeromonads from water and fish is a potential public health threat and molecular genotyping can be helpful to study epidemiology of the pathogen.

SIGNIFICANCE AND IMPACT OF THE STUDY

A high proportion of isolates recovered from diverse water sources, particularly potable drinking water and fish samples carried one or more enterotoxin genes thereby indicating a potential pathogenic nature of isolates from these sources. The genetic relatedness was detected amongst many isolates recovered from water sources and fish samples indicating circulation of familiar virulent clones in the aquatic environments.

Increase in ST-11 serogroup W Neisseria meningitidis invasive meningococcal disease in Canada, 2016-2018

BACKGROUND

Many countries have experienced increases in invasive meningococcal disease (IMD) due to a serogroup W Neisseria meningitidis (MenW) strain of the multilocus sequence type (ST)-11 clonal complex (CC). MenW ST-11 was first reported in Ontario, Canada, in 2014. By 2016, this strain caused IMD in five provinces and was responsible for 18.8% of the IMD cases in Canada.

OBJECTIVE

To provide an update on invasive MenW disease in Canada including the strain characteristics, specimen source of isolates, age, sex and geographic distribution of cases.

METHODS

N. meningitidis from culture-positive IMD cases are routinely submitted to the National Microbiology Laboratory (NML) for serogroup, serotype, serosubtype and sequence type analysis. The data from January 1, 2016 to December 31, 2018 were analyzed by calculating the proportion of IMD cases caused by MenW compared with other serogroups. In addition, trends based on age, sex and geographic distribution of cases and specimen source of isolates were analyzed based on information on specimen requisition forms.

RESULTS

Over the 3-year period, 292 individual IMD case isolates were analyzed. The percentage of IMD case isolates typed as MenW more than doubled from 19% (n=15) to 44% (n=51) in 2018 when MenW became the most common serogroup, exceeded the number of MenB, MenC or MenY. In total, 93 MenW case isolates were identified, 91% (n=85) belonged to the ST-11 CC. The increase in MenW affected all age groups (but was most common in those older than 60) and both sexes, and occurred across the country but most prevalent in western Canada. The most common specimen source was blood.

CONCLUSION

In 2018, MenW was the most common serogroup for isolates received by the NML from culture-positive IMD cases in Canada. Over 90% of the MenW serogroup isolates belonged to the ST-11 CC. The quadrivalent ACWY meningococcal conjugate vaccine protects against IMD caused by strains in the A, C, W or Y serogroups and therefore may protect against IMD caused by the new MenW ST-11 strain; however, more research is needed. The emergence of variant strains highlight the importance of strain characterization in IMD surveillance and research.

Whole-genome sequencing and characterization of an antibiotic resistant Neisseria meningitidis B isolate from a military unit in Vietnam

Background

Invasive meningococcal disease (IMD) persists in military units in Vietnam despite the availability of antibiotics and vaccines. A hindrance to reducing the incidence of IMD in Vietnam is a lack of molecular data from isolates of the causative agent, Neisseria meningitidis from this country. Here, we characterized key genetic and epidemiological features of an invasive N. meningitidis isolate from a military unit in Vietnam using whole-genome sequencing.

Methods

Neisseria meningitidis was isolated from a conscript admitted for meningitis and tested against seven antibiotics. DNA from the isolate was extracted and sequenced using the Illumina HiSeq platform. Denovo assembly and scaffolding were performed to construct a draft genome assembly, from which genes were predicted and functionally annotated. Genome analysis included epidemiological characterization, genomic composition and identification of antibiotic resistance genes.

Results

Susceptibility testing of the isolate showed high levels of resistance to chloramphenicol and diminished susceptibility to ampicillin and rifampicin. A draft genome of ~ 2.1 Mb was assembled, containing 2451 protein coding sequences, 49 tRNAs and 3 rRNAs. Fifteen coding sequences sharing ≥ 84% identity with known antibiotic resistance genes were identified. Genome analysis revealed abundant repetitive DNAs and two prophages. Epidemiological typing revealed newly described sequence type, antigenic finetype and Bexsero^® Antigen Sequence Typing (BAST). The BAST profile showed no coverage by either Bexsero^® or Trumenba^®.

Conclusions

Our results present the first genome assembly of an invasive N. meningitidis isolate from a military unit in Vietnam. This study illustrates the usefulness of whole genome sequencing (WGS) analysis for epidemiological and antibiotic resistance studies and surveillance of IMD in Vietnam.

Meningococcal disease burden and transmission in crowded settings and mass gatherings other than Hajj/Umrah: A systematic review

BACKGROUND

Mass gatherings (MGs) such as the Hajj and Umrah pilgrimages are known to amplify the risk of invasive meningococcal disease (IMD) due to enhanced transmission of the organism between attendees. The burden of IMD at MGs other than Hajj and Umrah has not previously been quantified through a systematic review.

METHODS

A systematic search for relevant articles in PubMed and Embase was conducted using MeSH terms; this was buttressed by hand searching. Following data abstraction, a narrative synthesis was conducted to quantify the burden of IMD at MGs and identify potential risk factors and mitigation measures.

RESULTS

Thirteen studies reporting occurrence of IMD at MGs or similar crowded settings were identified. Eight studies reported cases or outbreaks in MGs of ≥1000 people; five others reported IMD in other crowded settings; all occurred between 1991 and 2015. All age groups were involved in the identified studies; however the majority of cases (∼80%) were young people aged 15-24 years. The number of affected people ranged from one to 321 cases and the overall crude estimate of incidence was calculated as 66 per 100,000 individuals. Serogroups A, C, B and W were identified, with serogroups A and C being most common. Of 450 cases of IMD reported in non-Hajj/Umrah MGs, 67 (14.9%) had fatal outcomes.

CONCLUSION

IMD outbreaks at non-Hajj/Umrah MGs are generally much smaller than Hajj-related outbreaks and affect mainly young people. Health education and vaccination should be considered for attendees of high risk non-Hajj/Umrah MGs, especially those involving adolescents and young adults.

Molecular characterization of Neisseria meningitidis isolates recovered from 11-19-year-old meningococcal carriers in Salvador, Brazil

Characterization of meningococci isolated from the pharynx is essential towards understanding the dynamics of meningococcal carriage and disease. Meningococcal isolates, collected from adolescents resident in Salvador, Brazil during 2014, were characterized by multilocus sequence typing, genotyping or whole-genome sequencing. Most were nongroupable (61.0%), followed by genogroups B (11.9%) and Y (8.5%). We identified 34 different sequence types (STs), eight were new STs, distributed among 14 clonal complexes (cc), cc1136 represented 20.3% of the nongroupable isolates. The porA and fetA genotypes included P1.18,25-37 (11.9%), P1.18-1,3 (10.2%); F5-5 (23.7%), F4-66 (16.9%) and F1-7 (13.6%). The porB class 3 protein and the fHbp subfamily A (variants 2 and 3) genotypes were found in 93.0 and 71.0% of the isolates, respectively. NHBA was present in all isolates, and while most lacked NadA (94.9%), we detected the hyperinvasive lineages B:P1.19,15:F5-1:ST-639 (cc32); C:P1.22,14-6:F3-9:ST-3780 (cc103) and W:P1.5,2:F1-1:ST-11 (cc11). This is the first report on the genetic diversity and vaccine antigen prevalence among N. meningitidis carriage isolates in the Northeast of Brazil. This study highlights the need for ongoing characterization of meningococcal isolates following the introduction of vaccines and for determining public health intervention strategies.

Characterization of Oropharyngeal Carriage Isolates of Neisseria meningitidis in Healthy Korean Adolescents in 2015

The meningococcus carriage rate is age-dependent, with a high prevalence in adolescents and young adults. This cross-sectional study aimed to estimate the oropharyngeal carriage rate of meningococcus among healthy Korean adolescents and its relationship with several population characteristics. The survey was conducted from April to May 2015 among 1,460 first-year high-school students in 9 high schools located in Gyeonggi province, Korea. Each student answered a short questionnaire assessing risk factors for carriage, and posterior pharyngeal wall swab samples were obtained. These samples were cultured on meningococcus-selective media, with colonies resembling meningococci identified using the Vitek® MS system (bioMérieux, Marcy l'Etoile, France). All isolates were characterized by molecular serogrouping and multilocus sequence typing (MLST). Meningococci were identified from 3.4% (49/1,460) swabs. Current smokers had significantly higher carriage rates than non-smokers (8.2% vs. 2.9%, P = 0.002), and boys had significantly higher carriage rates than girls (4.4% vs. 1.6%, P = 0.004). Serogroup B was the most common serogroup, followed by serogroup C, then 29E and Y. Twenty-seven different sequence types (STs) were identified; the most common were ST-3091, ST-11278, and ST-44. These belonged to clonal complexes (CCs) 269, 32, and 41/44, respectively, known as the hypervirulent clones. Evaluating meningococcal carriage is important to understand the epidemiology of meningococcal disease; however, little data exist in Korea. Similar to western countries, meningococcal serogroup B has emerged in Korea, and hypervirulent clones were identified. It is necessary to monitor the genetic and serologic characteristics of circulating meningococci and to assess the potential strain coverage of meningococcal vaccines.

Meningococcal Carriage in Military Recruits and University Students during the Pre MenB Vaccination Era in Greece (2014-2015)

Purpose

The aim of the study was to estimate the meningococcal carriage rate and to identify the genotypic characteristics of the strains isolated from healthy military recruits and university students in order to provide data that might increase our understanding on the epidemiology of meningococcus and obtain information which helps to evaluate the potential effects on control programs such as vaccination.,

Methods

A total of 1420 oropharyngeal single swab samples were collected from military recruits and university students on voluntary basis, aged 18–26 years. New York City Medium was used for culture and the suspected N. meningitidis colonies were identified by Gram stain, oxidase and rapid carbohydrate utilization tests. Further characterisation was carried out by molecular methods (multiplex PCR, MLST, WGS).

Results

The overall carriage rate was of 12.7%; 15% and 10.4% for recruits and university students respectively. MenB (39.4%) was the most prevalent followed by MenY (12.8%) and MenW (4.4%). Among the initial 76 Non Groupable (NG) isolates, Whole Genome Sequence Analysis (WGS) revealed that 8.3% belonged to MenE, 3.3% to MenX and 1.1% to MenZ, while, 53 strains (29.4%) were finally identified as capsule null. Genetic diversity was found among the MenB isolates, with 41/44 cc and 35 cc predominating.

Conclusion

Meningococcal carriage rate in both groups was lower compared to our previous studies (25% and 18% respectively) with predominance of MenB isolates. These findings, help to further our understanding on the epidemiology of meningococcal disease in Greece. Although the prevalence of carriage seems to have declined compared to our earlier studies, the predominant MenB clonal complexes (including 41/44cc and 35cc) are associated with invasive meningococcal disease.

Invited review: Neisseria meningitidis lipopolysaccharides in human pathology

Neisseria meningitidis causes meningitis, fulminant septicemia or mild meningococcemia attacking mainly children and young adults. Lipopolysaccharides (LPS) consist of a symmetrical hexa-acyl lipid A and a short oligosaccharide chain and are classified in 11 immunotypes. Lipid A is the primary toxic component of N. meningitidis . LPS levels in plasma and cerebrospinal fluid as determined by Limulus amebocyte lysate (LAL) assay are quantitatively closely associated with inflammatory mediators, clinical symptoms, and outcome. Patients with persistent septic shock, multiple organ failure, and severe coagulopathy reveal extraordinarily high levels of LPS in plasma. The cytokine production is compartmentalized to either the circulation or to the subarachnoid space. Mortality related to shock increases from 0% to > 80% with a 10-fold increase of plasma LPS from 10 to 100 endotoxin units/ml. Hemorrhagic skin lesions and thrombosis are caused by up-regulation of tissue factor which induces coagulation, and by inhibition of fibrinolysis by plasminogen activator inhibitor 1 (PAI-1). Effective antibiotic treatment results in a rapid decline of plasma LPS (half-life 1—3 h) and cytokines, and reduced generation of thrombin, and PAI-1. Early antibiotic treatment is mandatory. Three intervention trials to block lipid A have not significantly reduced the mortality of meningococcal septicemia.

Meningococcal Two-Partner Secretion Systems and Their Association with Outcome in Patients with Meningitis

Two-partner secretion (TPS) systems export large TpsA proteins to the surface and extracellular milieu. In meningococci, three different TPS systems exist, and of these, TPS system 2 (TPS2) and TPS3 can be detected by the host's immune system. We evaluated the distribution of TPS systems among clinical isolates from two prospective cohort studies comprising 373 patients with meningococcal meningitis. TPS system 1 was present in 91% of isolates, and system 2 and/or 3 was present in 67%. The TPS system distribution was related to clonal complexes. Infection with strains with TPS2 and/or TPS3 resulted in less severe disease and better outcomes than infection with strains without these systems. Using whole-blood stimulation experiments, we found no differences in the host cytokine response between patients infected with TPS system 2 and 3 knockout strains and patients infected with a wild-type strain. In conclusion, meningococcal TPS system 2 and/or 3 is associated with disease severity and outcome in patients with meningitis.

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.

Global epidemiology of capsular group W meningococcal disease (1970-2015): Multifocal emergence and persistence of hypervirulent sequence type (ST)-11 clonal complex

Following an outbreak in Mecca Saudi Arabia in 2000, meningococcal strains expressing capsular group W (W) emerged as a major cause of invasive meningococcal disease (IMD) worldwide. The Saudi Arabian outbreak strain (Hajj clone) belonging to the ST-11 clonal complex (cc11) is similar to W cc11 causing occasional sporadic disease before 2000. Since 2000, W cc11 has caused large meningococcal disease epidemics in the African meningitis belt and endemic disease in South America, Europe and China. Traditional molecular epidemiologic typing suggested that a majority of current W cc11 burden represented global spread of the Hajj clone. However, recent whole genome sequencing (WGS) analyses revealed significant genetic heterogeneity among global W cc11 strains. While continued spread of the Hajj clone occurs in the Middle East, the meningitis belt and South Africa have co-circulation of the Hajj clone and other unrelated W cc11 strains. Notably, South America, the UK, and France share a genetically distinct W cc11 strain. Other W lineages persist in low numbers in Europe, North America and the meningitis belt. In summary, WGS is helping to unravel the complex genomic epidemiology of group W meningococcal strains. Wider application of WGS and strengthening of global IMD surveillance is necessary to monitor the continued evolution of group W lineages.

Meningococcemia in Adults: A Review of the Literature

We mainly refer to the acute setting of meningococcemia. Meningococcemia is an infection caused by Neisseria meningitidis, which has 13 clinically significant serogroups that are distinguishable by the structure of their capsular polysaccharides. N. meningitidis, also called meningococcus, is a Gram-negative, aerobic, diplococcus bacterium. The various consequences of severe meningococcal sepsis include hypotension, disseminated intravascular coagulation (DIC), multiple organ failure, and osteonecrosis due to DIC. The gold standard for the identification of meningococcal infection is the bacteriologic isolation of N. meningitidis from body fluids such as blood, cerebrospinal fluid (CSF), synovial fluid, and pleural fluid. Blood, CSF, and skin biopsy cultures are used for diagnosis. Meningococcal infection is a medical emergency that requires antibiotic therapy and intensive supportive care. Management of the systemic circulation, respiration, and intracranial pressure is vital for improving the prognosis, which has dramatically improved since the wide availability of antibiotics. This review of the literature provides an overview of current concepts on meningococcemia due to N. meningitidis infection.

Characterization of invasive Neisseria meningitidis strains from Québec, Canada, during a period of increased serogroup B disease, 2009-2013: phenotyping and genotyping with special emphasis on the non-carbohydrate protein vaccine targets

BACKGROUND

The epidemiology of invasive meningococcal disease (IMD) in Québec, Canada, has been dominated in the past decade by a clone of serogroup B (MenB) Neisseria meningitidis defined by multi-locus sequence typing (MLST) as sequence type (ST)-269. With the licensure of a new MenB vaccine Bexsero (4CMenB) in Canada, this study characterized invasive N. meningitidis recovered in Québec from 2009 to 2013, with an objective to examine the diversity of the 4CMenB vaccine antigens. Isolates were serogrouped by antisera and genogrouped by PCR, and further typed by whole cell ELISA for serotype and serosubtype antigens. Clonal analysis was done by MLST. Isolates were genotyped by analysis of their 4CMenB vaccine antigen genes of PorA, factor H binding protein (fHbp), Neisserial Heparin Binding Antigen (NHBA), and Neisseria Adhesin A (NadA).

RESULTS

Of the 263 IMD isolates analysed, 229, 16, 10, 7, and 1 belonged to MenB, MenY, MenW, MenC, and MenX, respectively. Of the 229 MenB, 159 (69.4 %) were typed as ST-269 clonal complex (CC); and they possessed a restricted number of three fHbp and five nhba gene alleles. Nine N. meningitidis isolates (eight MenB and one MenY) were found to possess at least one gene that encoded for an antigen that matched exactly with protein variants in the 4CMenB vaccine. Two MenB expressed PorA antigen P1.4 and possessed the nhba gene for peptide 2; four other MenB were predicted to have NHBA peptide 2; another two MenB were predicted to encode fHbp peptide 1.1; and a single MenY was found to have nadA gene for NadA peptide 8. In addition, another 172 isolates were found to possess genes for variant 1 fHbp peptides other than peptide 1.1 or NadA variant 1-2/3 peptides other than peptide 8; and therefore, may potentially be covered by 4CMenB.

CONCLUSION

The most prevalent clone of N. meningitidis in Quebec was ST-269 CC; and 96 % of the isolates in this CC were predicted to be covered by 4CMenB vaccine. Extensive genetic diversity was found in the other IMD isolates in Québec which might suggest a lower coverage by the vaccine when compared to the ST-269 MenB.

Clonal analysis of meningococci during a 26 year period prior to the introduction of meningococcal serogroup C vaccines

Meningococcal disease remains a public health burden in the UK and elsewhere. Invasive Neisseria meningitidis, isolated in Scotland between 1972 and 1998, were characterised retrospectively to examine the serogroup and clonal structure of the circulating population. 2607 isolates causing invasive disease were available for serogroup and MLST analysis whilst 2517 were available for multilocus sequence typing (MLST) analysis only. Serogroup distribution changed from year to year but serogroups B and C were dominant throughout. Serogroup B was dominant throughout the 1970s and early 1980s until serogroup C became dominant during the mid-1980s. The increase in serogroup C was not associated with one particular sequence type (ST) but was associated with a number of STs, including ST-8, ST-11, ST-206 and ST-334. This is in contrast to the increase in serogroup C disease seen in the 1990s that was due to expansion of the ST-11 clonal complex. While there was considerable diversity among the isolates (309 different STs among the 2607 isolates), a large proportion of isolates (59.9%) were associated with only 10 STs. These data highlight meningococcal diversity over time and the need for ongoing surveillance during the introduction of new meningococcal vaccines.

Synthesis of a tetrasaccharide and its glycoconjugate corresponding to the capsular polysaccharide of Neisseria meningitidis serogroup X and its immunochemical studies

A tetrameric unit of capsular polysaccharide of Neisseria meningitidis X has been synthesized and conjugated with tetanus toxoid. Their immunochemical property has been evaluated which indicates towards the development of a potential MenX vaccine.

A gene-by-gene population genomics platform: de novo assembly, annotation and genealogical analysis of 108 representative Neisseria meningitidis genomes

BACKGROUND

Highly parallel, 'second generation' sequencing technologies have rapidly expanded the number of bacterial whole genome sequences available for study, permitting the emergence of the discipline of population genomics. Most of these data are publically available as unassembled short-read sequence files that require extensive processing before they can be used for analysis. The provision of data in a uniform format, which can be easily assessed for quality, linked to provenance and phenotype and used for analysis, is therefore necessary.

RESULTS

The performance of de novo short-read assembly followed by automatic annotation using the pubMLST.org Neisseria database was assessed and evaluated for 108 diverse, representative, and well-characterised Neisseria meningitidis isolates. High-quality sequences were obtained for >99% of known meningococcal genes among the de novo assembled genomes and four resequenced genomes and less than 1% of reassembled genes had sequence discrepancies or misassembled sequences. A core genome of 1600 loci, present in at least 95% of the population, was determined using the Genome Comparator tool. Genealogical relationships compatible with, but at a higher resolution than, those identified by multilocus sequence typing were obtained with core genome comparisons and ribosomal protein gene analysis which revealed a genomic structure for a number of previously described phenotypes. This unified system for cataloguing Neisseria genetic variation in the genome was implemented and used for multiple analyses and the data are publically available in the PubMLST Neisseria database.

CONCLUSIONS

The de novo assembly, combined with automated gene-by-gene annotation, generates high quality draft genomes in which the majority of protein-encoding genes are present with high accuracy. The approach catalogues diversity efficiently, permits analyses of a single genome or multiple genome comparisons, and is a practical approach to interpreting WGS data for large bacterial population samples. The method generates novel insights into the biology of the meningococcus and improves our understanding of the whole population structure, not just disease causing lineages.

Surveillance of invasive Neisseria meningitidis with a serogroup Y update, Sweden 2010 to 2012

Binary file ES_Abstracts_Final_ECDC.txt matches

Implications of differential age distribution of disease-associated meningococcal lineages for vaccine development

New vaccines targeting meningococci expressing serogroup B polysaccharide have been developed, with some being licensed in Europe. Coverage depends on the distribution of disease-associated genotypes, which may vary by age. It is well established that a small number of hyperinvasive lineages account for most disease, and these lineages are associated with particular antigens, including vaccine candidates. A collection of 4,048 representative meningococcal disease isolates from 18 European countries, collected over a 3-year period, were characterized by multilocus sequence typing (MLST). Age data were available for 3,147 isolates. The proportions of hyperinvasive lineages, identified as particular clonal complexes (ccs) by MLST, differed among age groups. Subjects <1 year of age experienced lower risk of sequence type 11 (ST-11) cc, ST-32 cc, and ST-269 cc disease and higher risk of disease due to unassigned STs, 1- to 4-year-olds experienced lower risk of ST-11 cc and ST-32 cc disease, 5- to 14-year-olds were less likely to experience ST-11 cc and ST-269 cc disease, and ≥25-year-olds were more likely to experience disease due to less common ccs and unassigned STs. Younger and older subjects were vulnerable to a more diverse set of genotypes, indicating the more clonal nature of genotypes affecting adolescents and young adults. Knowledge of temporal and spatial diversity and the dynamics of meningococcal populations is essential for disease control by vaccines, as coverage is lineage specific. The nonrandom age distribution of hyperinvasive lineages has consequences for the design and implementation of vaccines, as different variants, or perhaps targets, may be required for different age groups.

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.

Rifaximin in the treatment of irritable bowel syndrome: is there a high risk for development of antimicrobial resistance?

Irritable bowel syndrome (IBS), a chronic, nonfatal illness is commonly encountered in clinical practice; however, treatment options are limited and often ineffectual. Despite this, there is increasing evidence that bacterial overgrowth in the bowel (dysbiosis) may be an etiological factor in IBS. This has lead to studies in which the antibiotic agent rifaximin has been used to reduce the microbial burden in the bowel, to some extent alleviating the symptoms of IBS. Rifaximin is a member of the rifamycin class of antibiotics, which when administered orally has the distinctions of being gut specific coupled with poor systemic absorption, characteristics that are suggested to limit the development of bacterial resistance. The rifamycins are currently used to treat serious human diseases including tuberculosis, meningococcal disease, methicillin-resistant Staphylococcus aureus and Clostridium difficile infections. The use of rifamycins in the treatment of these diseases is associated with the development of antibiotic resistance over time. When considering the importance of the rifamycins in the treatment of serious human diseases, the large number of patients affected by IBS, and the lack of scientific evidence available on the development of antibiotic resistance to rifaximin over the long-term when used in the gut, it is advisable that the use of rifaximin as a therapy for IBS should be limited to single, acute, short-term treatment.

Neisseria meningitidis serogroup B vaccine development

Neisseria meningitidis is an air-borne, gram-negative pathogen that actively invades its human host leading to the development of life-threatening pathologies. As one of the leading causes of death in the world, during an epidemic period N. meningitidis can be responsible for nearly 1000 new infections per 100,000 individuals. The bacterial species is further categorized into 13 serotypes, with five, A, B, C, W-135, and Y, being the most clinically relevant, causing the overwhelming majority of diseases. There are two contemporary, purified protein conjugate vaccines available that function by targeting serogroups A, C, W-135, and Y. Historically, serogroup B has posed a vaccination challenge; however, there are currently two vaccines in development able to target serotype B. This review will highlight N. meningitidis as a pathogen and explore the recent literature providing a current review of meningococcal vaccination development.

The changing epidemiology of meningococcal disease in Quebec, Canada, 1991-2011: potential implications of emergence of new strains

Background

In order to inform meningococcal disease prevention strategies, we analysed the epidemiology of invasive meningococcal disease (IMD) in the province of Quebec, Canada, 10 years before and 10 years after the introduction of serogroup C conjugate vaccination.

Methodology

IMD cases reported to the provincial notifiable disease registry in 1991–2011 and isolates submitted for laboratory surveillance in 1997–2011 were analysed. Serogrouping, PCR testing and assignment of isolates to sequence types (ST) by using multilocus sequence typing (MLST) were performed.

Results

Yearly overall IMD incidence rates ranged from 2.2–2.3/100,000 in 1991–1992 to 0.49/100,000 in 1999–2000, increasing to 1.04/100,000 in 2011. Among the 945 IMD cases identified by laboratory surveillance in 1997–2011, 68%, 20%, 8%, and 3% were due to serogroups B, C, Y, and W135, respectively. Serogroup C IMD almost disappeared following the implementation of universal childhood immunization with monovalent C conjugate vaccines in 2002. Serogroup B has been responsible for 88% of all IMD cases and 61% of all IMD deaths over the last 3 years. The number and proportion of ST-269 clonal complex has been steadily increasing among the identified clonal complexes of serogroup B IMD since its first identification in 2003, representing 65% of serogroup B IMD in 2011. This clonal complex was first introduced in adolescent and young adults, then spread to other age groups.

Conclusion

Important changes in the epidemiology of IMD have been observed in Quebec during the last two decades. Serogroup C has been virtually eliminated. In recent years, most cases have been caused by the serogroup B ST-269 clonal complex. Although overall burden of IMD is low, the use of a vaccine with potential broad-spectrum coverage could further reduce the burden of disease. Acceptability, feasibility and cost-effectiveness studies coupled with ongoing clinical and molecular surveillance are necessary in guiding public policy decisions.

Genetic and antigenic characterization of invasive endemic serogroup B Neisseria meningitidis from Ontario, Canada, in 2001-2010

This study examined the antigenic and genetic diversity of serogroup B Neisseria meningitidis (MenB) recovered from invasive meningococcal disease (IMD) cases in Ontario, Canada, over the period 2001-2010 during which no MenB outbreaks had occurred. MenB was found to be responsible for 39 % of all IMD cases, with the remaining cases caused mainly by serogroups Y (28 %), C (23.5 %) and W135 (8 %). One hundred and ninety-three individual MenB case isolates were collected and characterized. Of the 88 sequence types (STs) identified, 75 were grouped into 14 known clonal complexes (CCs), whilst 13 STs were not assigned to any known CC. Fifty-seven different PorA genotypes and 88 STs defined the diversity of invasive MenB in Ontario, which supported the endemic nature of MenB disease in Ontario. Despite the presence of the hypervirulent ST-41/44 and ST-32 CCs, no single ST was predominant and responsible for a large number of IMD cases. Although the Québec outbreak clone of ST-269 was also found in Ontario, the 20 case isolates were genetically diverse: they grouped into seven STs and did not have a predominant PorA genotype. eburst analysis identified a new CC responsible for 14.5 % of the MenB case isolates. The six most common PorA variable region 2 (VR2) genotypes (VR2-9, -4, -14, -16, -13-1 and -16-3) were found in 67 % of invasive MenB isolates.

Evolutionary and genomic insights into meningococcal biology

Epidemic disease caused by Neisseria meningitidis, the meningococcus, has been recognized for two centuries, but remains incompletely controlled and understood. There have been dramatic reductions in serogroup A and C meningococcal disease following the introduction of protein-polysaccharide conjugate vaccines, but there is currently no comprehensive vaccine against serogroup B meningococci. Genetic analyses of meningococcal populations have provided many insights into the biology, evolution and pathogenesis of this important pathogen. The meningococcus, and its close relative the gonococcus, are the only pathogenic members of the genus Neisseria, and the invasive propensity of meningococci varies widely, with approximately a dozen 'hyperinvasive lineages' responsible for most disease. Despite this, attempts to identify a 'pathogenome', a subset of genes associated with the invasive phenotypes, have failed; however, genome-wide studies of representative meningococcal isolates using high-throughput sequencing are beginning to provide details on the relationship of invasive phenotype and genotype in this fascinating organism and how this relationship has evolved.

Impact of vaccination during an epidemic of serogroup C meningococcal disease in Salvador, Brazil

To combat rising incidence of serogroup C meningococcal disease in the city of Salvador, Brazil, the Bahia state immunization program initiated routine childhood immunization with meningococcal C conjugate vaccine (MenC) in February 2010, followed by mass MenC vaccination of city residents 10-24 years of age from May through August 2010. We analyzed trends in incidence of reported cases of meningococcal disease and serogroup distribution among meningococcal isolates identified in hospital-based surveillance in Salvador from January 2000 to December 2011 and estimated vaccine effectiveness using the screening method. Annual incidence of serogroup C meningococcal disease increased from 0.1 cases per 100,000 population during 2000-2006 to 2.3 in 2009 and 4.1 in 2010, before falling to 2.0 per 100,000 in 2011. Estimated coverage of mass vaccination reached 80%, 67% and 41% among 10-14, 15-19 and 20-24 year olds, respectively. Incidence in 2011 was significantly lower than average rates in 2008-2009 among children <5 years, but reductions among 10-24 year olds were not significant. Among 10-24 year olds, a single dose of MenC vaccine was 100% effective (95% confidence interval, 79-100%) against serogroup C meningococcal disease. Low coverage in the population targeted for mass vaccination may have limited impact on ongoing transmission of serogroup C meningococcal disease despite high vaccine effectiveness.

Invasive serogroup B Neisseria meningitidis in Quebec, Canada, 2003 to 2010: persistence of the ST-269 clone since it first emerged in 2003

In the era after the introduction of the meningococcal serogroup C conjugate vaccine, from 1 January 2003 to 31 December 2010, serogroup B meningococci were the major cause of invasive meningococcal disease in the province of Québec, Canada, being responsible for 72% of all meningococcal disease cases. Of the 334 invasive serogroup B Neisseria meningitidis strains analyzed, 53.9% belonged to the ST-269 clonal complex (CC). Since it first emerged in 2003, the percentage of invasive serogroup B isolates that belonged to the ST-269 CC had increased from 35% in 2003 to 76% in 2010. Among the 180 meningococci in the ST-269 CC, 91.7% belonged to a single ST (ST-269). The most common PorA genotypes identified in the ST-269 CC were (i) VR1 19-1, VR2 15-11, VR3 36 (84%) and (ii) VR1 18-7, VR2 9, VR3 35-1 (9%). Cases of invasive disease due to the ST-269 CC were commonly found in those aged 11 to 19 years (30.5%) and 20 to 40 years (25.5%). Meningococci of the ST-269 CC were uncommon in other Canadian provinces. In contrast to the ST-269 CC, invasive serogroup B meningococci that belonged to the ST-41/44 CC were much more diverse genetically. However, one ST (ST-571), which is uncommon in the United States, accounted for 35% of all cases due to this CC. The current finding suggests that the ST-269 clone may indeed represent an emerging hypervirulent clone of meningococci.

Late repression of NF-κB activity by invasive but not non-invasive meningococcal isolates is required to display apoptosis of epithelial cells

Meningococcal invasive isolates of the ST-11 clonal complex are most frequently associated with disease and rarely found in carriers. Unlike carriage isolates, invasive isolates induce apoptosis in epithelial cells through the TNF-α signaling pathway. While invasive and non-invasive isolates are both able to trigger the TLR4/MyD88 pathway in lipooligosaccharide (LOS)-dependant manner, we show that only non-invasive isolates were able to induce sustained NF-κB activity in infected epithelial cells. ST-11 invasive isolates initially triggered a strong NF-κB activity in infected epithelial cells that was abolished after 9 h of infection and was associated with sustained activation of JNK, increased levels of membrane TNFR1, and induction of apoptosis. In contrast, infection with carriage isolates lead to prolonged activation of NF-κB that was associated with a transient activation of JNK increased TACE/ADAM17-mediated shedding of TNFR1 and protection against apoptosis. Our data provide insights to understand the meningococcal duality between invasiveness and asymptomatic carriage.

Phenotypic and molecular characterization of serogroup C Neisseria meningitidis associated with an outbreak in Bahia, Brazil

OBJECTIVE

To characterize meningococcal strains isolated from five cases of meningococcal disease (MD) associated with an outbreak in Trancoso - BA, occurred in October 2009. All cases, with the exception of a 39-year-old male, attended a dance party with approximately 1000 youngsters in a rural site.

MATERIALS AND METHODS

The epidemiological investigation was conducted by the Epidemiological Surveillance Service of Bahia State. Meningococcal strains were characterized at Adolfo Lutz Institute, the Brazilian National Reference Laboratory for Bacterial Meningitis by conventional techniques (serotype, serosubtype and antimicrobial susceptibility test) and by molecular methods (Pulsed-field gel electrophoresis - PFGE and Multilocus Sequence Typing - MLST).

RESULTS

The PFGE showed 2 closely related restriction profiles, designated as PFGE types A and A1, having 92% relatedness to each other. MLST characterization showed both A and A1 clones were ST-3780, which belongs to the ST-103 complex. All isolates displayed the phenotype C:23:P1.5 and were susceptible to all antibiotics tested.

CONCLUSIONS

This is the first reported MD outbreak associated with serogroup C ST-103 complex in Brazil, as well as the party and illicit drug-use associated outbreak.

Potential of recombinant opa proteins as vaccine candidates against hyperinvasive meningococci

Neisseria meningitidis causes half a million cases of septicemia and meningitis globally each year. The opacity (Opa) integral outer membrane proteins from N. meningitidis are polymorphic and highly immunogenic. Particular combinations of Opa proteins are associated with the hyperinvasive meningococcal lineages that have caused the majority of serogroup B and C meningococcal disease in industrialized countries over the last 60 years. For the first time, this genetic structuring of a diverse outer membrane protein family has been used to select a novel combination of representative antigens for immunogenicity testing. Fourteen recombinant Opa variants were produced and used in murine immunizations inducing an increase in specific antimeningococcal total IgG levels. All 14 Opa proteins elicited bactericidal antibodies against at least one hyperinvasive meningococcal isolate, and most isolates from each hyperinvasive lineage were killed by at least one Opa antiserum at a titer of 1:16 or greater. Cross-reactive bactericidal antibody responses were observed among clonal complexes. A theoretical coverage of 90% can be achieved by using a particular combination of 6 Opa proteins against an isolate collection of 227 recent United Kingdom disease cases. This study indicates the potential of Opa proteins to provide broad coverage against multiple meningococcal hyperinvasive lineages.

Emergence of 2 Neisseria meningitidis serogroup C clones in a French county

Between 2003 and 2007, we recovered 21 serogroup C Neisseria meningitidis isolates in the Haute-Vienne county of France. Multilocus sequence typing showed that 20 isolates belonged to the ST-11 clonal complex (8 to clone ET-15 and 12 to clone ET-37) and 1 to the ST-8 clonal complex.

A novel interpretation of structural dot plots of genomes derived from the analysis of two strains of Neisseria meningitidis

Neisseria meningitidis is the agent of invasive meningococcal disease, including cerebral meningitis and septicemia. Because the diseases caused by different clonal groups (sequence types) have their own epidemiological characteristics, it is important to understand the differences among the genomes of the N. meningitidis clonal groups. To this end, a novel interpretation of a structural dot plot of genomes was devised and applied; exact nucleotide matches between the genomes of N. meningitidis serogroup A strain Z2491 and serogroup B strain MC58 were identified, leading to the specification of various structural regions. Known and putative virulence genes for each N. meningitidis strain were then classified into these regions. We found that virulence genes of MC58 tend more to the translocated regions (chromosomal segments in new sequence contexts) than do those of Z2491, notably tending towards the interface between one of the translocated regions and the collinear region. Within the collinear region, virulence genes tend to occur within 16 kb of gaps in the exact matches. Verification of these tendencies using genes clustered in the cps locus was sufficiently supportive to suggest that these tendencies can be used to focus the search for and understanding of virulence genes and mechanisms of pathogenicity in these two organisms.

Proteome analysis of Neisseria meningitidis serogroup strains C associated with outbreaks in China

OBJECTIVE

During 2003-2005, an outbreak of meningitis due to Neisseria meningitidis serogroup C occurred in China. With the aim to find strain clues result in the final epidemics, the ancestral strain 053442, a clinical isolate, and a carrier strain 053426 with different gene type were analyzed.

METHODS

Clinical strain 053442 and carrier strain 053426 were cultured on GC agar plates under the same condition. Two-dimensional electrophoresis was performed using the pH 3-10 nonlinear IPG strips of 24 cm length, and all the protein spots were identified by matrix-assisted laser desorption/ionization time of flight spectrometry.

RESULTS

502 and 380 protein spots were identified in 053426 and 053442 respectively, relating to 266 and 202 different genes covering a wide range of cellular functions. The express volume and number of proteins involved in energy metabolism, protein synthesis and amino acid biosynthesis in 053426 were higher than in 053442. Virulence factor Opa, Opc and a series of proteins involved in pilus assembly and retraction were identified in 053442, which appear to be of primary importance in colonization and invasion of human cells. Compared to 053442, virulence protein species were less in 053426, with lower express volumes too. No Opa and Opc were detected in 053426.

CONCLUSIONS

The different protein expression profiles of the clinical strain 053442 and carrier strain 053426 in the present study provide some clues of the different pathogenicity of the two strains, which may account for result in the final epidemics.

Genetic and structural characterization of L11 lipooligosaccharide from Neisseria meningitidis serogroup A strains

The lipooligosaccharide (LOS) of immunotype L11 is unique within serogroup A meningococci. In order to resolve its molecular structure, we conducted LOS genotyping by PCR analysis of genes responsible for alpha-chain sugar addition (lgtA, -B, -C, -E, -H, and -F) and inner core substituents (lgtG, lpt-3, and lpt-6). For this study, we selected seven strains belonging to subgroup III, a major clonal complex responsible for meningococcal meningitis epidemics in Africa. In addition, we sequenced the homopolymeric tract regions of three phase-variable genes (lgtA, lgtG, and lot-3) to predict gene functionality. The fine structure of the L11 LOS of each strain was determined using composition and glycosyl linkage analyses, NMR, and mass spectrometry. The masses of the dephosphorylated oligosaccharides were consistent with an oligosaccharide composed of two hexoses, one N-acetyl-hexosamine, two heptoses, and one KDO, as proposed previously. The molar composition of LOS showed two glucose residues to be present, in agreement with lgtH sequence prediction. Despite phosphoethanolaminetransferase genes lpt-3 and lpt-6 being present in all seven Neisseria meningitidis strains, phosphoethanolamine (PEtn) was found at both O-3 and O-6 of HepII among the three ST-5 strains, whereas among the four ST-7 strains, only one PEtn was found and located at O-3 of the HepII. The L11 LOS was found to be O-acetylated, as was indicated by the presence of the lot-3 gene being in-frame in all of the seven N. meningitidis strains. To our knowledge, these studies represent the first full genetic and structural characterization of the L11 LOS of N. meningitidis. These investigations also suggest the presence of further regulatory mechanisms affecting LOS structure microheterogeneity in N. meningitidis related to PEtn decoration of the inner core.