Resistance of faecal cysts of Spironucleus muris to some physical factors and chemical substances.

The effect of 5 disinfectants, and of saturated zinc chloride solution + sodium chloride solution, 2.5% potassium dichromate solution, and 0.12% dimetridazole on faecal cysts of Spironucleus muris were tested in vitro. The resistance of the cysts to high and low temperatures, low pH, high osmotic pressure, centrifugation and desiccation was also tested. After treatment the morphology of the cysts was observed microscopically and their infectivity tested in vivo on sensitive thymus-deficient nude mice. The cysts ceased to be infective after treatment with most of usual disinfectants and by high temperature (45 degrees C for 30 min). They resisted 0.12% dimetridazole, low temperature (-196 degrees C), low pH (2.2), high osmotic pressure (distilled water and 30% 'Ficoll'), centrifugation (1500 g/20 min) and desiccation (room temperature for 14 days). These data may be useful for the control of Spironucleus muris infection in rodents and for cryopreservation of the parasite for experimental purposes.