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Emergence of short-lived meningococci causing focal epidemics can be associated with gene transfer from carriage-associated Neisseria

Charlene M.C. RodriguesiD, Jay LucidarmeiD, Rachel M. ExleyiD, Jack L. ClarkiD, Xilian BaiiD, Christopher D. BaylissiD, Meera A ChandiD, Stephen A Clark, Cynthia Nau CornelisseniD, Jeremy P. DerrickiD, Luke R. GreeniD, Natalie GrovesiD, Yaiza Gutierrez VazqueziD, Odile Barbara HarrisoniD, Keith A. JolleyiD, Samantha A McKeandiD, Richard E. MyersiD, Nicholas NoinajiD, Kasia Maria ParfittiD, Paolo RibecaiD, Ray BorrowiD, Martin C. J. MaideniD, Christoph M. TangiD

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In-depth summary

Claude Opus 5.5 · xhigh effort · 8 Nov 2026 · from the full text of version 1 (21 Sept 2026) · CC BY 4.0

A 21-case nightclub-linked meningococcal outbreak variant differed from its closest relatives by horizontal gene transfer from carriage-associated Neisseria, affecting iron acquisition and type IV pili genes.

Meningococcal outbreaks are highly unpredictable in duration and size. The paper compares outbreak genomes with their closest available relatives and proposes that gene acquisition from carriage-associated Neisseria yields highly invasive but short-lived variants, a pattern it also reports for 1990s C:cc11 outbreaks.

Key results

  1. SuggestedThe six Kent outbreak isolates were near-identical (ST-485, cc41/44, one LIN code), and genome-based and phenotypic antigen assays predicted them to be covered by licensed serogroup B vaccines.

    The six isolates differed at one core-gene allele (NEIS1452). fHbp MATS relative potency was 0.032-0.040 (positive bactericidal threshold >0.012). MEASURE fluorescence was 1846-2432 vs a protective threshold of 1000. NHBA relative potency was 0.309 for one isolate with a result (threshold >0.294). · Isolates from the Kent outbreak were highly…

  2. SuggestedAgainst its two closest relatives, the outbreak variant differed in many genes, with eight putative horizontal transfer events. Matches in PubMLST point to carriage-associated or other-lineage donors: cnl cc198, cc162 and N. cinerea.

    92 genes and 46 intergenic regions differed, 40 of the genes within horizontal transfer events. The tbp region matched cc198 in 838/859 genomes (97.3%) and the fur region in 795/830 (95.8%). The NEIS1437 allele was found in 531 of 559 cc162 genomes. The pilV region matched two N. cinerea isolates. · Differences between the outbreak variant and its…; HGT events in the outbreak variant affecting…; HGT events affecting Tfp

  3. SuggestedThree iron-acquisition regions changed. The outbreak TbpA has a shortened loop-3 helix, a feature predicted to alter transferrin binding and linked in database counts to invasive disease.

    In AlphaFold-based models, 75% of TbpA changes lay within 15 Å of the transferrin interface. Truncated-helix TbpA was in 453 of 84,755 Neisseria isolates (0.5%). In encapsulated meningococci, 106/116 (91.4%) truncated-helix isolates were from IMD vs 17,277/22,170 (77.9%); Fisher P<0.001, OR 3.00, 95% CI 1.57-5.75. · HGT events in the outbreak variant affecting…

  4. SuggestedType IV pili genes were a recurring target of recombination, in Kent and in the 1997 Southampton C:cc11 outbreak. The pilH-pilX region changed in both, with probable donors among non-pathogenic carried lineages.

    Six of 20 COG category N genes differed between Kent and a close relative (q=2.0e-5). Southampton: four outbreak isolates vs a closest relative showed 265 differences and 10 potential horizontal transfer events. Of genomes sharing the NEIS0828/NEIS0829 alleles (n=295), 92.2% were cnl cc198. · HGT events affecting Tfp; Pathway enrichment analysis; Analysis of other focal outbreaks of IMD

  5. SuggestedThe ST-485 background and the PorA of the sublineage may have favoured immune evasion: high-capsule-expression promoter alleles were more frequent in ST-485, and PorA VR2 P1.16-183 was predicted to be structurally atypical.

    High capsule expression was predicted for 173/416 ST-485 isolates (41.5%) vs 1061/4700 other cc41/44 (22.6%); chi-square 124.6297, p<0.0001. The 8-residue VR2 of P1.16-183 separated from other P1.16 variants in PCA of AlphaFold3 models and was predicted to fold into the barrel, likely hiding it from antibodies. · Characteristics shared by the outbreak variant…

Methods, data and reproducibility

Hybrid short- and long-read genomes of six outbreak isolates and two close relatives were compared locus by locus in PubMLST (wgMLST, phase variation, recombination donor searches). Structural modelling, pathway over-representation and retrospective analysis of 1990s C:cc11 outbreaks were added.

  • Six Kent 2026 outbreak isolates from blood (hybrid Illumina and Oxford Nanopore genomes); 21 cases in total, 15 confirmed by PCR · Neisseria meningitidis · n = 6 isolates (21 cases) · PubMLST isolate ids 1926231, 1930355, 1930356, 1930357, 1934266, 1930358; reference genome PubMLST id 193899
  • Two closest relatives from English IMD cases (2022 and 2023), hybrid genomes · Neisseria meningitidis · n = 2 isolates · PubMLST ids 194251 and 194252 (isolates 22MN0044, 23MN0134)
  • Meningococcal genomes in PubMLST used for LIN code and donor searches · Neisseria meningitidis · n = 48,019 genomes (accessed 5th August 2026)
  • PubMLST Neisseria isolates used to count TbpA truncated-helix alleles · Neisseria spp. · n = 84,755 isolates
  • 1990s C:cc11 ET-15 outbreaks (Cardiff, Southampton, Rotherham) and 2,016 ET-15 genomes; Southampton compared with a closest relative · Neisseria meningitidis · n = 2,016 ET-15 genomes; Southampton 4 isolates · PubMLST id 644 (relative L93/4286)
Methods & tools
PubMLST, PhasomeIt v1.1.5, AlphaFold3, PISA, Bio3D, PyMOL, PROKKA, PANEROO, COGclassifier v2.0.0, eggNOG-mapper v2, MATS, MEASURE
Data & accessions
https://pubmlst.org/
Reagents & environment
Tool versions given for PhasomeIt (v1.1.5), COGclassifier (v2.0.0) and eggNOG-mapper (v2, eggNOG 5.0); no container or requirements file mentioned.
Reproducibility gaps
No analysis code repository is given, and the custom tool for intergenic allele calling is not linked. The LbpA structure used for comparison is unpublished. Hybrid genomes are on PubMLST; the 15 PCR-only cases have no genomes.
Limitations (4)
  • No contemporary carriage isolates exist, and the closest relatives were isolated three to four years earlier, so when each genetic change or phase variation state arose is unclear. · stated by the authors
  • The functional consequences of many of the polymorphisms (e.g. in Tfp genes and tbp/lbp alleles) remain unclear; links to carriage and sustained transmission need functional studies. · stated by the authors
  • Only six of the 21 cases yielded isolates; the other 15 were confirmed by PCR only. · noted in this summary
  • The comparison rests on one outbreak and only two closest relatives, so changes specific to the outbreak variant cannot be separated from background variation in the sublineage. · noted in this summary

Read this if you work on bacterial outbreak genomics and want a worked example of attributing recombination donors and structural effects, or you follow invasiveness versus transmission trade-offs in meningococci.

Citations
1

Abstract

In March 2026, an unusually large outbreak of invasive meningococcal disease (IMD) in Kent, UK, was linked to attendance at one nightclub over a single weekend. The outbreak organism was a Neisseria meningitidis variant belonging to the longstanding hyperinvasive genotype, cc41/44. Using genome analysis of six isolates from patients, alongside >48,000 meningococcal genomes, we investigated whether the outbreak variant had acquired traits potentially contributing to the highly invasive phenotype. The six isolates were capsular group B, sequence type (ST-)485, and essentially indistinguishable, consistent with the focal nature of the outbreak. Compared with their closest available relatives, we found changes mediated by phase variation, nucleotide variation, and horizontal gene transfer (HGT) involving adhesins, iron-acquisition systems (including Transferrin and Lactoferrin binding proteins, and FetA), and Type IV pili (Tfp), factors which affect bacteria-bacteria and bacteria-host interactions. These changes occurred in a ST-485 sub-lineage that expressed capsule at high levels and a PorA porin with a truncated surface-exposed epitope, both of which are predicted to reduce immune recognition. Donors for the HGT events were predominantly carriage-associated N. meningitidis and Neisseria cinerea. We show that meningococcal variants responsible for previous focal outbreaks have not been seen subsequently. We propose that focal outbreaks of IMD are caused by meningococcal variants that may have acquired traits from non- or less invasive organisms, but subsequently these variants disappear, as their highly invasive phenotype is inconsistent with sustained transmission. Ongoing disease surveillance alongside carriage studies are therefore essential to inform public health risk and manage epidemic IMD.

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