FIG 2.

Shedding of emm3 serotype GAS in infant CD-1 mice is inoculum dependent and influenced by the index-to-contact ratio. (a and b) Shedding titers of MGAS10870 from index mice in CD-1 litters inoculated at 1:1 (a) and 1:2 (b) index-to-contact ratios were detected during the acute shedding phase (days 1 to 3 postinoculation). (c and d) Shedding titers (CFU) of MGAS10870 from index mice in CD-1 litters inoculated at 1:1 (c) and 1:2 (d) index-to-contact ratios were detected throughout the monitoring period (days 1 to 9 postinoculation). (e and f) Shedding titers of MGAS10870 from contact mice in the same such litters were likewise assessed. The median shed titers, detected daily, are shown. Litters are indicated by the inocula (CFU) administered in the key adjacent to the graphs, and days postinoculation are enumerated on the x axis. The limit of detection is indicated by a dotted line (shedding titer, 1 CFU). Statistically significant differences in median shed titers were determined between inocula (black) and between index-to-contact ratios (red) by a Mann-Whitney U test (*, P < 0.05; **, P < 0.01; ***, P < 0.001; #, P < 0.0001).