Impact of silver and copper on the survival of amoebae and ciliated protozoa in vitro

The efficacy of 1:10 silver/copper combinations for inactivation of Hartman nella vermiformis amoebas and the ciliated protozoan Tetrahymena pyriformis in vitro was studied. Tetrahymena and Hartmannella/isolate 19 were inactiv ated for 2 log steps by 100 + 1000 mu g/l Ag + Cu. Hartmannella/isolate 21 was more resistent. 500 + 5000 mu g/l produced only a 0.6 log reduction. Th e investigations clearly showed that levels within the limit of the German drinking water regulation (10+100 mu g/l Ag + Cu) could not inactivate thes e protozoas in vitro.