DHFR and Opportunistic infection: Early concerns regarding HIV-1 co-infection prompted studies that suggested mutations in parasite dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) due to use of trimethoprim-sulfamethoxazole (Bactrim), a commonly prescribed preventative for HIV-associated opportunistic infections, provided cross resistance to the antimalarial sulfadoxine-pyrimethamine (SP) (Iyer et al., 2001).