ICHTHYOPHTHIRIUS-MULTIFILIIS - AXENIC ISOLATION AND SHORT-TERM MAINTENANCE IN SELECTED MONOPHASIC MEDIA

All stages in the life cycle of Ichthyophthirius multifiliis were succ essfully isolated axenically, without loss of viability, by use of 1% penicillin:streptomycin solution (100 IU cm-3:100 mug cm-3). Survival and development of each stage was investigated in selected monophasic media at 20-degrees-C. Parasite survival was extended over that observ ed in water controls, suggesting that both parasitic and free-living s tages are capable of some degree of nutrient uptake. The tomite surviv ed within the cyst for a maximum of 22 days when incubated in EMEM wit hout added serum (EMEM-S) and diluted 50:50 with distilled water. Viab le theronts survived for up to 5 days within EMEM, 3 days longer than controls, and mature trophonts survived, with no further development, for up to 16 days within Glasgow modification of EMEM with added 10% s erum. Successful encystment and excystment was dependent on water and occurred only in diluted media. Delayed encystment was achieved by inc ubation in concentrated media, the production of sterile, viable thero nts being delayed for up to 96 h within EMEM-S, 72 h later than normal ly observed in the aquatic environment. The significance of the result s are discussed with regard to the routine maintenance of the parasite and future prospects for in vitro culture.