title: Plasmodium falciparum: variations in p-aminobenzoic acid requirements as related to sulfadoxine sensitivity.
abstract: Plasmodium falciparum, Thai strain FCM-5S sensitive to sulfadoxine, was grown continuously for 1 year in a medium with a low concentration of p-aminobenzoic acid (PABA) without the emergence of a sulfadoxine-resistant line. The minimum PABA-requirement for growth of sulfadoxine-sensitive Thai strains in vitro was found to be 25.0 ng/ml, whereas resistant Burmese and Gambian strains completed their schizogony in the absence of PABA. Cultivation in dialyzed and nondialyzed human serum suggested that the sulfadoxine-resistant parasite might use another serum factor in place of PABA for folate biosynthesis, thus overcoming the effect of sulfadoxine, a PABA antagonist. The significantly lower rate of [14C]sulfadoxine incorporation into erythrocytes infected with sulfadoxine-resistant strains strongly supports this suggestion.
mesh_terms: D010129:4-Aminobenzoic Acid / Q000378:metabolism; D003470:Culture Media / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial; D004912:Erythrocytes / Q000469:parasitology; D006801:Humans; D010963:Plasmodium falciparum / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013413:Sulfadoxine / Q000494:pharmacology*; D013424:Sulfanilamides / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D003470:Culture Media; D013424:Sulfanilamides; D013413:Sulfadoxine; D010129:4-Aminobenzoic Acid