ABSTRACT
BACKGROUND: Results from numerous studies point convincingly to correlations between mutations at selected genes and phenotypic resistance to antimalarials in Plasmodium falciparum isolates. In order to move molecular assays for point mutations on resistance-related genes into the realm of applied tools for surveillance, we investigated a selection of P. falciparum isolates that were imported during the year 2001 into Europe to study the prevalence of resistance-associated point mutations at relevant codons. In particular, we tested for parasites which were developing resistance to antifolates and chloroquine. The screening results were used to map the prevalence of mutations and, thus, levels of potential drug resistance in endemic areas world-wide. RESULTS: 337 isolates have been tested so far. Prevalence of mutations that are associated with resistance to chloroquine on the pfcrt and pfmdr genes of P. falciparum was demonstrated at high levels. However, the prevalence of mutations associated with resistance to antifolates at the DHFR and DHPS genes was unexpectedly low, rarely exceeding 60% in endemic areas. CONCLUSIONS: Constant screening of imported isolates will enable TropNetEurop to establish a screening tool for emerging resistance in endemic areas.
Subject(s)
ATP-Binding Cassette Transporters/genetics , Antimalarials/pharmacology , Drug Resistance/genetics , Membrane Proteins/genetics , Plasmodium falciparum/drug effects , Protozoan Proteins/genetics , Animals , Chloroquine/pharmacology , Codon , Dihydropteroate Synthase/genetics , Drug Resistance, Multiple/genetics , Europe , Folic Acid Antagonists/pharmacology , Humans , Malaria, Falciparum/parasitology , Membrane Transport Proteins , Plasmodium falciparum/genetics , Plasmodium falciparum/isolation & purification , Point Mutation , Tetrahydrofolate Dehydrogenase/genetics , TravelABSTRACT
Point mutations in the dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) genes of Plasmodium falciparum can lead to an increasing resistance of P. falciparum to pyrimethamine/sulphadoxine. We examined the prevalence of these mutations in 36 samples from Colombia. Analysed by polymerase chain reaction (PCR) for infection with P. falciparum, 25 (69%) tested positive. These positive isolates were tested further for point mutations in the genes of DHFR (codons 16, 51, 59, 108 and 164) and DHPS (codons 436, 437, 540, 581 and 613) by nested PCR and following mutation-specific restriction enzyme digestion. Gene mutations occurred in both the DHFR and DHPS gene of the Colombian isolates, suggesting that resistance to antifolate drugs exists or may develop soon in Colombia.