Use of a semi-nested PCR diagnosis test to evaluate antifolate resistance of Plasmodium falciparum isolates

The antifols, inhibitors of the dihydrofolate reductase (DHFR), such as pyrimethamine and proguanil, have been used against Plasmodium falciparum in the areas where chloroquine resistance is widespread. This use has selected resistant strains in Southeast Asia and South America. The resistance is correlated with point mutations in precise positions of the DHFR gene. A reliable semi-nested PCR diagnosis test was established and used to determine the genotypic features of 29 isolates of P. falciparum originating from Africa. The results obtained by the PCR technique were compared with those of the in vitro drug sensitivity test. Some isolates were found to be polyclonal. Among the mutations tested, only mutations on codon 108 which generate an asparagine induce a decrease in sensitivity to pyrimethamine and cycloguanil, whereas mutation on codon 59 strengthens resistance to both antifols. No mutation on codon 16 or codon 164 was found.