title: Evidence for a genetic alteration of dihydrofolate reductase associated with amethopterin resistance in Diplococcus pneumoniae.
mesh_terms: D004352:Drug Resistance, Microbial; D066298:In Vitro Techniques; D008727:Methotrexate; D008967:Molecular Biology; D009154:Mutation; D013296:Streptococcus pneumoniae / Q000201:enzymology*; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism*
chemical_list: D013762:Tetrahydrofolate Dehydrogenase; D008727:Methotrexate