A, Comparison of cepA transcription between invasive and non-invasive isolates. Target gene transcripts were measured as the no. of copies per 10,000 copies of the housekeeping gene gyrA, with reference to a plasmid of known copy number. Data are grouped by isolate source. Reference strain: H305, M1T1 scarlet fever isolate. Strain H292 is shown as an outlier. Invasive isolates expressed more cepA than did non-invasive isolates, (P<0.046, Mann-Whitney U test). B, Correlation between copies of cepA and copies of hasA. The expression of cepA correlated positively with the expression of hasA (r= 0.67, Spearman rank correlation; P<0.003).