Sensitivity of Encephalitozoon cuniculi to various temperatures, disinfectants and drugs

Spores of Encephalitozoon cuniculi were exposed to various temperature or to disinfectants, and their infectivity was then tested on monolayer cultures of canine kidney cells. The maximum survival time for spores suspended in medium 199 was 1 day at -20 degrees C, 98 days at 4 degrees C, 6 days at 22 degrees C, and 2 days at 37 degrees C. Only 2.5% survived 30 min at 56 degrees C. Boiling for 5 min or autoclaving at 120 degrees C for 10 min killed all spores. Dry spores survived less than a week at 4 degrees C but at least 4 weeks at 22 degrees C. Exposure for 30 min to recommended working concentrations of 9 of the 11 disinfectants tested killed all spores. The growth-inhibition effect of 7 antibiotics and chemotherapeutics was studied on canine kidney cell culture inoculated with E. cuniculi. None could completely inhibit growth. The most effective was chloroquine phosphate which, at a concentration of 12.5 mg per 1000 ml culture medium and during a test period of 8 weeks, reduced the harvest of E. cuniculi to 31% of that from inoculated, untreated cultures.