All media were tested in the pour plate method with an overlay of the same medium, since in (inter)- national standards of ISO, DIN, and NMKL, only pour plate methods are described. Plates were incubated anaerobically at 37 jC for 18F2 h. Different methods to obtain anaerobiosis were used with the collaborative trial [e.g., Anaerocult, Anaerogen (Oxoid), Anoxomat, and anaerobic chamber].