The maintenance of stock strains of trichomonads by freezing

Abstract

The ability of four species of trichomonads to withstand freezing was investigated with a view to storage of stock cultures. Of the conditions investigated the most satisfactory was found to be storage at – 79° C. following slow freezing, the protozoa being suspended in medium containing 10% glycerol. T. gallinae was the most easily preserved and survived even without glycerol for 6 months. No observations on survival beyond this period have yet been made so the possible maximum time of survival is not known. T. vaginalis remained viable for four months but deteriorated in storage and had died out after 6 months. The sample of T. hominis containing 10 % glycerol was still viable after 6 months at – 79° C., but in the presence of 5 % glycerol survival was not observed beyond 4 months. T. foetus could not be preserved under any of the conditions tested. The possible implications of these results are discussed.