Basic studies on group B streptococcal (GBS) culture medium

Yeast extract and Serum are said to be necessary for the pigmentation of Group B Streptococcus (hereafter, GBS). We're examined the necessity of these for the GBS pigmentation. Firstly, we examined the following four types of culture media. (1) The medium in which serum was excluded from the New Granada medium (hereafter, called Basic medium). (2) New Granada medium (hereafter, S medium). (3) The medium in which Yeast extract was added to (1) (hereafter, Y medium). (4) The medium in which added Serum and Yeast extract were added to (1) (hereafter, SY medium). As for GBS tested (7 serotypes, 27 strains), Basic medium showed the strongest pigmentation potency, but, S and SY medium showed the weakest. About the quickness of pigmentation initiation, similar to the potency above, Basic medium was the quickest, followed by Y medium, and then S medium and SY medium. Among the media examined, there were no differences in the relationships between the quantity of GBS applied and the positive ratio of each media.>From these results, among four types of the media, Basic medium is thought to be the best one for the GBS detection.