FIG 2.

Neighbor-Net graphs constructed with 1,241 of 1,600 and 1,189 of 1,600 loci defined as the core genome in the PubMLST database (A and B, respectively). The Neisseria meningitidis serogroup Y isolates were collected in (A) Sweden, 1995 to 2012 (n = 185), and (B) England, Wales, and Northern Ireland, 2010 to 2011 and 2011 to 2012 (n = 143), and Maryland, 1999 (strain types NM220 and NM233 [6], marked in red boxes). Isolates belonging to the most common invasive N. meningitidis serogroup Y strain types (characterized by 12 genes) in Sweden, YI, YII, YIII (9, 12), and YIV, are found among the isolates in the pink, purple, green, and gray areas, respectively. Isolates belonging to the predominating strain type in England, Wales, and Northern Ireland (Table 1) are found among the isolates in the light blue area. The genetic distance was defined as number of loci with allelic differences.