THE SENSITIVITY OF AXENIC 200-NIH ENTAMOEBA-HISTOLYTICA TO BACITRACIN AND ITS ZINC SALT

This study extends the previous knowledge of the action of bacitracin zinc against xenic cultures of Entamoeba histolytica. Results presented here, using axenic E. histolytica, confirm the enhanced activity of bacitracin zinc as compared to native bacitracin and demonstrate that this enhancement is due to a direct effect upon the trophozoite. In the presence of zinc, amoebastatic concentrations of bacitracin became amoebacidal. The expression of the amoebacidal characteristics of 5 g/l bacitracin zinc following 24-35 h incubation coincided with the return of cell division by amoeba exposed to the same concentration of native bacitracin. The activity of both bacitracin and bacitracin zinc on trophozoites was unaffected by autoclaving, indicating a mode of action different from that exerted on Staphylococcus aureus. In contrast to previous clinical observations, no synergism could be detected between bacitracin and neomycin.