Invasive meningococcal capsular group Y disease, England and Wales, 2007-2009.

Enhanced national surveillance for invasive meningococcal disease in England and Wales identified an increase in laboratory-confirmed capsular group Y (MenY) disease from 34 cases in 2007 to 44 in 2008 and 65 in 2009. For cases diagnosed in 2009, patient median age at disease onset was 60 years; 39% of patients had underlying medical conditions, and 19% died. MenY isolates causing invasive disease during 2007-2009 belonged mainly to 1 of 4 clonal complexes (cc), cc23 (56% of isolates), cc174 (21%), cc167 (11%), and cc22 (8%). The 2009 increase resulted primarily from sequence type 1655 (cc23) (22 cases in 2009, compared with 4 cases each in 2007 and 2008). cc23 was associated with lpxL1 mutations and meningitis in younger age groups (<25 years); cc174 was associated with nonmeningitis, particularly pneumonia, in older age groups (>65 years). The increase in MenY disease requires careful epidemiologic and molecular monitoring.

Longitudinal study of the molecular epidemiology of Campylobacter jejuni in cattle on dairy farms.

Multilocus sequence typing (MLST), an accurate and phylogenetically robust characterization method for population studies of Campylobacter, was applied to Campylobacter jejuni isolates (n = 297) from the fecal samples of cattle from five dairy farms in Cheshire, United Kingdom, collected throughout 2003. The population dynamics of the C. jejuni strains, as identified by the occurrence of sequence types and clonal complexes, demonstrated variations within and between cattle populations over time. Three clonal lineages have emerged to predominate among the cattle isolates, namely, the ST-61 complex (24.2%), ST-21 complex (23.6%), and ST-42 complex (20.5%). This provided further evidence that the ST-61 clonal complex may present a cattle-adapted C. jejuni genotype. In addition, the ST-42 clonal complex may also represent an important cattle-associated genotype. Strong geographical associations for these genotypes were also found among the farms. This is the first longitudinal study and the largest study to date for C. jejuni involving cattle populations using MLST for accurate strain characterization. This study shows the important associations between cattle and C. jejuni clonal complexes ST-61, ST-21, and ST-42, and it suggests that cattle and/or dairy products are likely to be a source of the human Campylobacter gastroenteritis caused by such genotypes. The reported findings have significant implications for the design of effective intervention strategies for disease control and prevention.

Meningococcal carriage within households in the African meningitis belt: A longitudinal pilot study.

OBJECTIVES: Carriers of Neisseria meningitidis are a key source of transmission. In the African meningitis belt, where risk of meningococcal disease is highest, a greater understanding of meningococcal carriage dynamics is needed. METHODS: We randomly selected an age-stratified sample of 400 residents from 116 households in Bamako, Mali, and collected pharyngeal swabs in May 2010. A month later, we enrolled all 202 residents of 20 of these households (6 with known carriers) and collected swabs monthly for 6 months prior to MenAfriVac vaccine introduction and returned 10 months later to collect swabs monthly for 3 months. We used standard bacteriological methods to identify N. meningitidis carriers and fit hidden Markov models to assess acquisition and clearance overall and by sex and age. RESULTS: During the cross-sectional study 5.0% of individuals (20/400) were carriers. During the longitudinal study, 73 carriage events were identified from 1422 swabs analyzed, and 16.3% of individuals (33/202) were identified as carriers at least once. The majority of isolates were non-groupable; no serogroup A carriers were identified. CONCLUSIONS: Our results suggest that the duration of carriage with any N. meningitidis averages 2.9 months and that males and children acquire and lose carriage more frequently in an urban setting in Mali. Our study informed the design of a larger study implemented in seven countries of the African meningitis belt.

Differences between culture & non-culture confirmed invasive meningococci with a focus on factor H-binding protein distribution.

OBJECTIVES: To compare the distribution of capsular groups and factor H-binding protein (fHBP) variants among meningococcal isolates and non-culture clinical specimens and to assess the representativeness of group B isolates amongst group B cases as a whole. METHODS: A PCR sequencing assay was used to characterise fHBP from non-culture cases confirmed from January 2011 to December 2013. These were compared to genotypic data derived from whole genome analysis of isolates received during the same period. RESULTS: Group W and Y strains were more common among isolates than non-culture strains. The distribution of fHBP variants among group B non-culture cases generally reflected that seen in the corresponding isolates. Nonetheless, the non-culture subset contained a greater proportion of fHBP variant 15/B44, associated with the ST-269 cluster sublineage. CONCLUSIONS: Differences in capsular group and fHBP distribution among culture and non-culture cases may be indicative of variation in strain viability, diagnostic practice, disease severity and/or clinical presentation. Future analyses combining clinical case information with laboratory data may help to further explore these differences. Group B isolates provide a good representation of group B disease in E&W and, therefore, can reliably be used in fHBP strain coverage predictions of recently-licensed vaccines.

Genomic epidemiology of age-associated meningococcal lineages in national surveillance: an observational cohort study.

BACKGROUND: Invasive meningococcal disease (IMD) is a worldwide health issue that is potentially preventable with vaccination. In view of its sporadic nature and the high diversity of Neisseria meningitidis, epidemiological surveillance incorporating detailed isolate characterisation is crucial for effective control and understanding the evolving epidemiology of IMD. The Meningitis Research Foundation Meningococcus Genome Library (MRF-MGL) exploits whole-genome sequencing (WGS) for this purpose and presents data on a comprehensive and coherent IMD isolate collection from England and Wales via the internet. We assessed the contribution of these data to investigating IMD epidemiology. METHODS: WGS data were obtained for all 899 IMD isolates available for England and Wales in epidemiological years 2010-11 and 2011-12. The data had been annotated at 1720 loci, analysed, and disseminated online. Information was also available on meningococcal population structure and vaccine (Bexsero, GlaxoSmithKline, Brentford, Middlesex, UK) antigen variants, which enabled the investigation of IMD-associated genotypes over time and by patients' age groups. Population genomic analyses were done with a hierarchical gene-by-gene approach. FINDINGS: The methods used by MRF-MGL efficiently characterised IMD isolates and information was provided in plain language. At least 20 meningococcal lineages were identified, three of which (hyperinvasive clonal complexes 41/44 [lineage 3], 269 [lineage 2], and 23 [lineage 23]) were responsible for 528 (59%) of IMD isolates. Lineages were highly diverse and showed evidence of extensive recombination. Specific lineages were associated with IMD in particular age groups, with notable diversity in the youngest and oldest individuals. The increased incidence of IMD from 1984 to 2010 in England and Wales was due to successive and concurrent epidemics of different lineages. Genetically, 74% of isolates were characterised as encoding group B capsules: 16% group Y, 6% group W, and 3% group C. Exact peptide matches for individual Bexsero vaccine antigens were present in up to 26% of isolates. INTERPRETATION: The MRF-MGL represents an effective, broadly applicable model for the storage, analysis, and dissemination of WGS data that can facilitate real-time genomic pathogen surveillance. The data revealed information crucial to effective deployment and assessment of vaccines against N meningitidis. FUNDING: Meningitis Research Foundation, Wellcome Trust, Public Health England, European Union.

Genotypic analysis of meningococcal factor h-binding protein from non-culture clinical specimens.

Factor H-Binding Protein (fHbp) is an outer membrane protein antigen included in two novel meningococcal group B vaccines and, as such, is an important typing target. Approximately 50% of meningococcal disease cases in England and Wales are confirmed using real-time PCR on non-culture clinical specimens only. Protocols for typing fHbp from this subset of cases have not yet been established. Here we present a nested PCR-based assay designed to amplify and sequence fHbp from non-culture clinical specimens. From analytical sensitivity experiments carried out using diluted DNA extracts, an estimated analytical sensitivity limit of 6 fg/µL of DNA (<3 genome copies/µL) was calculated. The sensitivity of the assay was shown to be comparable to the ctrA-directed real-time PCR assay currently used to confirm invasive disease diagnoses from submitted clinical specimens. A panel of 96 diverse, patient-matched clinical specimen/isolate pairs from invasive disease cases was used to illustrate the breadth of strain coverage for the assay. All fHbp alleles sequenced from the isolates matched those derived from previous whole genome analyses. The first-round PCR primer binding sites are highly conserved, however an exceptional second-round PCR primer site mismatch in one validation isolate prevented amplification. In this case, amplification from the corresponding clinical specimen was achieved, suggesting that the use of a nested PCR procedure may compensate for any minor mismatches in round-two primer sites. The assay was successful at typing 91/96 (94.8%) of the non-culture clinical specimens in this study and exhibits sufficient sensitivity to type fHbp from the vast majority of non-culture clinical specimens received by the Meningococcal Reference Unit, Public Health England.

Genetic distribution of noncapsular meningococcal group B vaccine antigens in Neisseria lactamica.

The poor immunogenicity of the meningococcal serogroup B (MenB) capsule has led to the development of vaccines targeting subcapsular antigens, in particular the immunodominant and diverse outer membrane porin, PorA. These vaccines are largely strain specific; however, they offer limited protection against the diverse MenB-associated diseases observed in many industrialized nations. To broaden the scope of its protection, the multicomponent vaccine (4CMenB) incorporates a PorA-containing outer membrane vesicle (OMV) alongside relatively conserved recombinant protein components, including factor H-binding protein (fHbp), Neisseria adhesin A (NadA), and neisserial heparin-binding antigen (NHBA). The expression of PorA is unique to meningococci (Neisseria meningitidis); however, many subcapsular antigens are shared with nonpathogenic members of the genus Neisseria that also inhabit the nasopharynx. These organisms may elicit cross-protective immunity against meningococci and/or occupy a niche that might otherwise accommodate pathogens. The potential for 4CMenB responses to impact such species (and vice versa) was investigated by determining the genetic distribution of the primary 4CMenB antigens among diverse members of the common childhood commensal, Neisseria lactamica. All the isolates possessed nhba but were devoid of fhbp and nadA. The nhba alleles were mainly distinct from but closely related to those observed among a representative panel of invasive MenB isolates from the same broad geographic region. We made similar findings for the immunogenic typing antigen, FetA, which constitutes a major part of the 4CMenB OMV. Thus, 4CMenB vaccine responses may impact or be impacted by nasopharyngeal carriage of commensal neisseriae. This highlights an area for further research and surveillance should the vaccine be routinely implemented.

Invasive meningococcal disease in England and Wales: implications for the introduction of new vaccines.

A number of meningococcal vaccines have either been recently licensed or are in late-phase clinical trials. To inform national vaccination policy, it is important to define the burden of disease and the potential impact of any new vaccine. This study describes the epidemiology of invasive meningococcal disease across all age groups in England and Wales for recent epidemiological years between 2006 and 2010. The Health Protection Agency (HPA) conducts enhanced national meningococcal surveillance through a combination of clinical and laboratory reporting. Between 2006/07 and 2010/11, the average annual incidence of invasive meningococcal disease across all age groups was 2.0/100,000. Capsular group B (MenB) accounted for 87% (4777/5471) cases, with an overall incidence of 1.8/100,000. The highest MenB incidence observed among infants (36.2/100,000) where cases increased from birth to 5 months of age then gradually declined. An annual average of 245 MenB cases occurred in infants (135 in those aged ≤ 6 months) representing 26% (and 14%) of all MenB cases, respectively. After infancy, MenB rates declined until the age of 12 years, rising to a second smaller peak at 18 years. MenB case fatality ratio (CFR) was 5.2% (247/4777 cases) overall and was highest among ≥ 65 year-olds (28/161; 17.4%). The largest number of deaths (n=125), however, occurred among <5 year-olds. Clonal complexes cc269 and cc41/44 each accounted for around a third of cases across the age groups. Other capsular groups rarely caused invasive disease, although capsular group Y (MenY) cases more than doubled from 35 in 2006/07 to 86 in 2010/11. Thus, universal meningococcal vaccination with an effective broad-spectrum formulation has potential to prevent most disease, particularly if the vaccine is immunogenic early in infancy, but, there is currently little justification for routine quadrivalent ACWY conjugate vaccination in the UK, although the increase in MenY disease warrants continued surveillance.

Molecular targets in meningococci: efficient routine characterization and optimal outbreak investigation in conjunction with routine surveillance of the meningococcal group B vaccine candidate, fHBP.

In 2007, recommendations were proposed for the molecular typing of meningococci. Multilocus sequence typing (MLST) was recommended to guide national and international disease management and facilitate studies of population biology and evolution. Sequencing of porA variable regions (VRs) 1 and 2 and the fetA VR was recommended for monitoring antigenic distribution and investigating potential outbreaks. porB characterization was recommended if further resolution was required. Several investigational "group B" meningococcal vaccines, including two in the advanced stages of development, incorporate factor H-binding protein (fHBP). The requirement for routine surveillance of fhbp places additional pressure on reference laboratories, both financially and in terms of labor. This study investigated the optimal and most efficient molecular typing schemes for (i) routine meningococcal characterization and (ii) the investigation of potential outbreaks, in conjunction with routine surveillance of fhbp. All invasive disease isolates received by the Health Protection Agency Meningococcal Reference Unit between July 2007 and June 2008 (n = 613) were characterized in terms of capsular group, porA, fetA VR, fhbp, and sequence type (ST). Following capsular grouping and porA genosubtyping, several predominant capsular group-porA combinations were identified. The levels of additional resolution afforded by fetA and fhbp were comparable and partially complementary. fhbp constitutes an effective substitute for fetA as a routine marker of antigenic distribution, thereby reducing costs in conjunction with fhbp surveillance. MLST afforded markedly superior resolution overall and is the optimal scheme for investigating outbreaks in which (i) typing data are unavailable for the index case or (ii) the index case possesses a known, predominant capsular group-porA repertoire.