FIG 4.

Production of hyaluronic acid capsule reduces GAS adherence to human tonsillar epithelial cells and enhances GAS survival in whole human blood. Hyaluronic acid capsule content (a), adherence to human tonsillar epithelial cells (HTEpiC) (b), and survival in whole human blood (c) were measured in capsule-negative (emm3^ΔhasA and emm87^ΔcovS) and capsule-positive [emm87(hasA^emm3) and emm87(hasA^emm3-ΔcovS)] strains and their respective isogenic parent (emm87 and emm3) strains. The mean hyaluronic acid content was normalized to CFU counts of analyzed GAS cultures and was measured from two biological replicates performed in quadruplicate. Failure to detect capsule is indicated (ND, not detected). The mean percentages of HTEpiC adherence and standard errors of the means (SEM) are shown, calculated from two biological replicates measured in quadruplicate. Adherent emm87(hasA^emm3-ΔcovS) bacteria were not detected in several replicates. The mean multiplication factors of GAS in whole human blood and SEM are shown, calculated from biological replicates in blood from 3 donors, performed in quadruplicate. Significance was determined by a t test (**, P < 0.01; ***, P < 0.001; #, P < 0.0001).