Axenization of Entamoeba histolytica, a Korean strain YS-27

In the present communication, YS-27, a Korean strain of Entamoeba histolytica is described for the isolation and establishment of axenic cultivation. E. histolytica, designated as strain "YS-27", was isolated from the pus of a hepatic abscess obtained from a 72 year old inpatient of August 10, 1969. Specimens, were obtained by needle aspiration, inoculated immediately and weekly cultured in a modified diphasic medium at 37 degrees C. Strain YS-27 had been maintained for more than 15 years by weekly subculture until February, 1985. These cultures were transferred to a monoxenic TTY-SB medium seeded with a trypanosomatid of the genus Crithidia. Penicillin G, 2 to 10 x 10(3) International units and Streptomycin, 2 to 10 mg per 100 ml, were added to the cultures to eliminate the bacteria. After more than one year later, these two organisms were well maintained by transfer every 3 or 4 days until January, 1986 at 37 degrees C in TTY-SB medium in the absence of other microorganisms. These monoxenic cultures were then transferred to TYI-S-33 medium. Strain YS-27 alone had not been growing at the time of transfer, but when overlaid with Crithidia at intervals of 3 to 4 days, strain YS-27 propagated well. The Crithidia died out several weeks later after several passages. Beginning in April, 1986, strain YS-27, was successfully established in axenic culture in TYI-S-33 medium and has been maintained in continuous culture and multiplied well to present.