RESUMEN
OBJECTIVES: To assess the extent of drug resistance in Uige through molecular genetic analysis and to test whether the dhfr triple mutant alleles present in Angola are of southeast Asian origin. METHODS: Seventy-one samples of blood from children admitted to the Pediatric Emergency Unit of Uige Provincial Hospital in 2004 were screened for resistance mutations at pfcrt, pfmdr1, pfdhfr, pfdhps and pfATPase6. RESULTS: Mutations in pfcrt (codon76), pfmdr1 (codon86), pfdhfr (codons 51, 59, 108) and pfdhps (codons 436, 437) were common. Among the 66 isolates for which we were able to determine complete genetic information 13.7% carried all seven of these mutations. Flanking microsatellite analysis revealed the triple mutant pfdhfr was derived from the southeast Asian lineage, while the N51I+S108N double mutant pfdhfr alleles are a local origin. pfATPase6 mutations were rare and S769N was not found. CONCLUSION: The parasite population of Uige Angola has high frequency mutations in pfcrt, dhfr and dhps associated with resistance to chloroquine and sulphadoxine pyrimethamine, reflecting past reliance on these two drugs which were the mainstay of treatment until recently. Our findings show that drug resistance in Uige has occurred through a combination of local drug pressure and the regional and international dispersal of resistance mutant alleles.
Asunto(s)
Antimaláricos/uso terapéutico , Resistencia a Múltiples Medicamentos/genética , Malaria Falciparum/tratamiento farmacológico , Proteínas de Transporte de Membrana/genética , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/genética , Proteínas Protozoarias/genética , Pirimetamina/uso terapéutico , Angola , Niño , Genotipo , Humanos , Malaria Falciparum/genética , Repeticiones de Microsatélite/genética , Mutación/genéticaRESUMEN
BACKGROUND: Although the molecular basis of resistance to a number of common antimalarial drugs is well known, a geographic description of the emergence and dispersal of resistance mutations across Africa has not been attempted. To that end we have characterised the evolutionary origins of antifolate resistance mutations in the dihydropteroate synthase (dhps) gene and mapped their contemporary distribution. METHODS AND FINDINGS: We used microsatellite polymorphism flanking the dhps gene to determine which resistance alleles shared common ancestry and found five major lineages each of which had a unique geographical distribution. The extent to which allelic lineages were shared among 20 African Plasmodium falciparum populations revealed five major geographical groupings. Resistance lineages were common to all sites within these regions. The most marked differentiation was between east and west African P. falciparum, in which resistance alleles were not only of different ancestry but also carried different resistance mutations. CONCLUSIONS: Resistant dhps has emerged independently in multiple sites in Africa during the past 10-20 years. Our data show the molecular basis of resistance differs between east and west Africa, which is likely to translate into differing antifolate sensitivity. We have also demonstrated that the dispersal patterns of resistance lineages give unique insights into recent parasite migration patterns.
