Abstract
1) Cysts of Entamoeba histolytica in human stool were collected and made bacteria-free. To these cysts were added human and murine intestinal bacterial flora separately and cultivated. These cultivations were inoculated directly into the liver of rats. Amoebae associated with murine intestinal flora produced far more frequently the amoebic liver abscesses than those associated with human intestinal flora.
2) By the injection of antibiotics following the inoculation of amoebae, abscesses produced were mostly minute in size and amoebae were detected from none of them.
3) By the serial transplantation of amoebae from the abscesses into the liver of rats, the rate of the abscess production attained almost 100% and positive detection of amoebae from abscess also increased from one passage to another.
4) Addition of the associated bacteria of this liver-passed, highly virulent strain restored much of the infectivity of a strain which had been maintained in the culture media for more than 18 months and had almost lost the infectivity to the rat liver.
