Genomic analysis of serogroup Y Neisseria meningitidis isolates reveals extensive similarities between carriage and disease-associated organisms

Background: Neisseria meningitidis is a frequent colonizer of the human nasopharynx, with asymptomatic carriage providing the reservoir for invasive, disease-causing strains. Serogroup Y (MenY) strains are a major cause of meningococcal disease. High-resolution genetic analyses of carriage and disease isolates can establish epidemiological relationships and identify potential virulence factors.
Methods: Whole-genome sequence data were obtained for 99 MenY carriage isolates recovered in the United Kingdom during 1997–2010. Sequences were compared to those of 73 MenY invasive isolates recovered during 2010–2011, using a gene-by-gene approach.
Results: Comparisons across 1605 core genes resolved 91% of isolates into one of 8 clusters containing closely related disease and carriage isolates. Six clusters contained carried meningococci isolated during 1997–2001, suggesting temporal stability. One cluster of isolates, predominately sharing the designation Y: P1.5-1,10-1: F4-1: ST-1655 (cc23), was resolved into one subcluster with 86% carriage isolates and a second with 90% invasive isolates. These subclusters were defined by specific allelic differences in 5 core genes encoding glycerate kinase (glxK), valine-pyruvate transaminase (avtA), superoxide dismutase (sodB), and 2 hypothetical proteins.
Conclusions: High-resolution genetic analyses detected long-term temporal stability and temporally overlapping carriage and disease populations for MenY clones but also evidence of a disease-associated clone.