Bacterial Strains and Growth
Six of 10 S. equi strains used were kindly provided by Dr. James Musser at Methodist Hospital, Houston, Texas, and these strains were isolated more than 20 years ago from horses with strangles in the Eastern U.S. (4 strains), Brazil (1 strain), and Finland (1 strain). The other 4 strains were isolated in 2003 from horses with strangles in Livingston (designated strain SEM1) [10], Pony, Great Fall, and Norris in Montana. GAS strain MGAS5005 (serotype M1) has been described [11]. Escherichia coli Novablue and BL21(DE3) (Novagen, Madison, Wis.) were used for gene cloning and protein expression, respectively. S. equi and GAS strains were routinely grown in Todd-Hewitt broth (Difco Laboratories, Detroit, Mich.) supplemented with 0.2% yeast extract (THY) in 5% CO2 at 37°C. THY agar and tryptose agar with 5% sheep blood (Becton Dickinson, Cockeysville, Md.) were used as the solid media.