Transmission of S.pyogenes is hampered by loss of covR/S regulation.

Naïve five week old female FVB/n recipients co-mingled at a D:R ratio of 3∶5 with female FVB/n mice infected with either the emm75 wild type strain or it’s isogenic ΔcovR/S strain (5 ×10⁸ cfu per dose) and sampled after the introduction of the donor mice. Donor mice had >5000 cfu recovered from direct nasal sampling throughout the experiment. The ΔcovR/S strain transmitted significantly less well to recipients compared to the wild type strain (A, n = 15 recipients per group, AUC analysis, followed by Mann-Whitney U test). Line indicates median, error bars indicate interquartile range. Settle plates exposed to the air in the cages revealed no significant differences in the bacteria deposited on the surface of the plates by mice infected with the strain, or the ΔcovR/S strain (B, n = 4 plates per cage, AUC analysis followed by Mann-Whitney U test p>0.05) Data is shown for individual animals with medians indicated by black line.