YI-S, A CASEIN-FREE MEDIUM FOR AXENIC CULTIVATION OF ENTAMOEBA-HISTOLYTICA, RELATED ENTAMOEBA, GIARDIA-INTESTINALIS AND TRICHOMONAS-VAGINALIS

Pancreatic digests of casein are major ingredients of media used in th e axenic cultivation of lumen-dwelling parasitic protozoa, especially Entamoeba, Giardia, and trichomonads. The digest used almost exclusive ly in the development of these media, Medo-Peptone (Trypticase(R) BBL) , has not been available since 1981. Moreover, none of dozens of simil ar type digests tested since then in our laboratory has proved equal t o Medo-Peptone, and in the last two years it has become increasingly d ifficult to obtain new batches which will support even modest growth o f Entamoeba histolytica. In response to this problem we have developed a casein-free medium, YI-S, consisting of a nutrient broth, vitamin m ixture and serum. We recommend it as a replacement for the casein-depe ndent medium TYI-S-33, currently the most widely used for axenic cultu re of Entamoeba histolytica and other lumen-dwellers.