title: Evidence for capsule switching between carried and disease-causing Neisseria meningitidis strains.
abstract: Changing antigenic structure such as with capsule polysaccharide is a common strategy for bacterial pathogens to evade a host immune system. The recent emergence of an invasive W:2a:P1.7-2,4 sequence type 11 (ST-11) strain of Neisseria meningitidis in New Zealand, an uncommon serogroup/serotype in New Zealand disease cases, was investigated for its genetic origins. Molecular typing of 107 meningococcal isolates with similar serotyping characteristics was undertaken to determine genetic relationships. Results indicated that the W:2a:P1.7-2,4 strain had emerged via capsule switching from a group C strain (C:2a:P1.7-2,4). Neither the upstream nor downstream sites of recombination could be elucidated, but sequence analysis demonstrated that at least 45 kb of DNA was involved in the recombination, including the entire capsule gene cluster. The oatWY gene carried by the W:2a:P1.7-2,4 strain contained the insertion sequence element IS1301, one of five variants of oatWY found in group W135 strains belonging to the carriage-associated ST-22 clonal complex. This suggested that the origin of the capsule genes carried by the invasive W:2a:P1.7-2,4 strain is carriage associated. These results provide novel evidence for the long-standing dogma that disease-associated strains acquire antigenic structure from carriage-associated strains. Moreover, the capsule switch described here has arisen from the exchange of the entire capsule locus.
authors.affiliation: Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Beddek
authors.forename: Ming-Shi
authors.initials: MS
authors.lastname: Li
authors.forename: J Simon
authors.initials: JS
authors.lastname: Kroll
authors.forename: T William
authors.initials: TW
authors.lastname: Jordan
authors.forename: Diana R
authors.initials: DR
authors.lastname: Martin
mesh_terms: D016667:Bacterial Capsules / Q000235:genetics* / Q000276:immunology*; D015373:Bacterial Typing Techniques; D002353:Carrier State / Q000276:immunology / Q000382:microbiology*; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D006801:Humans; D008589:Meningococcal Infections / Q000276:immunology / Q000382:microbiology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009345:Neisseria meningitidis / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*; D009520:New Zealand; D012150:Polymorphism, Restriction Fragment Length; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D014774:Virulence
chemical_list: D004251:DNA Transposable Elements; D004269:DNA, Bacterial