Fig. 3

Growth of mid-log phase GAS on different plating media. Bland–Altman percentage difference of THY-agar, HBA and THY-TTC. The plots compare each replicate of each dilution with the sample from the same culture plated on THY-TTC agar and either HBA (a) or THY-agar (b). The Y axis is based on the formula [100 × (THY-TTC agar–HBA or THY agar)/average of the two points] and the X axis is the average of the two points. The biases of −0.30 and −5.02 are less than the cut-off of ±10 % which show plating on THY-TTC is sufficiently analogous to plating on either of the currently accepted methods. The dotted-lines represent the 95 % limits of agreement and range from −69.09 to 68.48 with HBA and −51.83 to 41.80 with THY agar. c–e show representative images of cultures grown on HBA, THY-TTC and THY-agar respectively. For the comparison with HBA, a series of five dilutions was plated for 16 strains in triplicate, of which 70 counts fell between 10 and 200 colonies. For the comparison with THY-agar, a series of five dilutions was plated for five strains in triplicate, of which 26 counts fell between 10 and 200 colonies