FIG 3.

Neighbor-Net graph constructed with 1,387 of 1,600 core genes from all Swedish Neisseria meningitidis strains belonging to the predominant serogroup Y strain type YI (9, 12) collected from 1995 to 2012 (n = 83). The two main clusters (assessed visually) are referred to as subtype 1 (n = 52) and subtype 2 (n = 23) and have been circled in horizontal and vertical stripes, respectively. Three isolates from the United Kingdom which share the same genetic profile as the Swedish predominant serogroup Y strain type YI have also been included. The serogroup Y strain NM233 from Maryland is representative of the dominating strain type from the late 1990s in the United States (6). The genetic distance was defined as the number of loci with allelic differences.