The plates were incubated at 37 oC for 24–48 h except for the MRS plates which were incubated at 37 oC for 48–72 h under microaerophilic conditions. In all cases, the incubation period was extended until visible colonies appeared. White, small, round colonies from the MSS and BHI agar were recovered and placed into BHI broth and incubated at 37 oC. Colonies with similar characteristics from MRS agar were transferred to MRS broth.