Mutants of Acanthamoeba castellanii resistant to erythromycin, chloramphenicol, and oligomycin.

Cell lines of Acanthamoeba castellanii resistant to erythromycin (EryR), chloramphenicol (CapR), and oligomycin (OliR) have been isolated. These may be the first such mutants for A. castellanii. These mutants have been phenotypically stable for 2 years, surviving storage and vegetative multiplication in the absence of drugs. Resistance was specific for each drug, but double mutants (e.g. EryRCapR) were obtained by stepwise selection. Mutant frequencies were determined in multiwell plates; less than 10 colony forming units (CFU/10(5) amebas were observed in wild-type populations 12 days after incubation in 500 microgram Ery/ml, 2.5 mg Cap/ml, or 15 microgram Oli/ml. After 30 days, averages of 100 CFU/10(5) amebas were observed in Ery and Cap, whereas, frequencies for Oli remained unchanged. Frequencies for EryR and CapR were consistent with rates of recovery from these drugs in batch cultures. We were unable to obtain spontaneous mutants resistant to cycloheximide, emetine, 5-fluorodeoxyuridine, or ethidium bromide. EryR, CapR and OliR could be mitochondria mutants.