S U M M A R Y Mycoplasmas are common contaminants of eukaryotic cells grown in tissue culture. A commercially available Mycoplasma Removal Agent (MRA) was therefore assessed for its effect on tachyzoites of Neospora caninum, in order to determine its suitability for further use in parasite cell cultures. Analyses of tachyzoite and excreted-secreted proteins and antigens by SDS-PAGE and Western blotting show that MRA treatment results in the rapid selection of a mutant population that differs

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... m the control and parental lines in its protein and antigen content. The treatment of N. caninum cultures with MRA is therefore not recommended for the eradication of Mycoplasma.