Distribution of phase ON and OFF mspA genes in carriage and disease isolates by serogroup.

aStatistically significant difference in the frequency of the mspA phase ON phenotype between MenB and MenY carriage isolates (p0.0001).bStatistically significant difference in the frequency of the mspA phase ON phenotype between MenB and MenY invasive isolates (p0.0001).cIncludes 15 strains from ST-11 which harbor a mutation in mspA interrupting the gene. All 15 strains were phase OFF at the polyC tract.