The Development of a Pyrimethamine-Resistant Line of Toxoplasma under in Vitro Conditions

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  • National Institute of Allergy and Infectious Diseases, Bethesda 14, Maryland


  1. 1.A pyrimethamine-resistant line of Toxoplasma at least 640 times more resistant than the parent strain was developed in vitro.
  2. 2.The resistant nature of this line was retained for at least 3 months when the parasite was grown in the absence of pyrimethamine.
  3. 3.A pyrimethamine-requiring line of Toxoplasma could not be developed.
  4. 4.The drug-resistant nature of this line of Toxoplasma was not demonstrable in vivo.

Author Notes

Present address: Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases.

Laboratory of Tropical Diseases.