Rapid selection of dhfr mutant allele in Plasmodium falciparum isolates after the introduction of sulfadoxine/pyrimethamine in combination with 4-aminoquinolines in Papua New Guinea

• Published in: Infection, genetics and evolution Vol. 6; no. 6; pp. 447 - 452
• Main Authors: Mita, Toshihiro, Kaneko, Akira, Hwaihwanje, Ilomo, Tsukahara, Takahiro, Takahashi, Nobuyuki, Osawa, Hikota, Tanabe, Kazuyuki, Kobayakawa, Takatoshi, Björkman, Anders
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-11-2006
• Subjects: Alleles; Aminoquinolines - administration & dosage; Aminoquinolines - therapeutic use; Animals; Chloroquine; Combination therapy; Dhfr; Dhps; Dihydropteroate Synthase - genetics; Drug Combinations; Drug Resistance, Multiple - genetics; Drug Therapy, Combination; Humans; Malaria, Falciparum - drug therapy; Malaria, Falciparum - epidemiology; Malaria, Falciparum - parasitology; Medicin och hälsovetenskap; Microsatellite; Mutation; Papua New Guinea - epidemiology; Plasmodium falciparum; Plasmodium falciparum - enzymology; Plasmodium falciparum - genetics; Polymorphism, Genetic; Pyrimethamine - administration & dosage; Pyrimethamine - therapeutic use; Resistance; Selection, Genetic; Sulfadoxine - administration & dosage; Sulfadoxine - therapeutic use; Sulfadoxine/pyrimethamine; Tetrahydrofolate Dehydrogenase - genetics; Papua New Guinea; Resistance; Dhfr; Plasmodium falciparum; Microsatellite; Sulfadoxine/pyrimethamine; Chloroquine; Dhps; Combination therapy
• ISSN: 1567-1348; 1567-7257
• DOI: 10.1016/j.meegid.2006.02.004

To overcome the declining efficacy of the 4-aminoquinolines in Papua New Guinea, sulfadoxine/pyrimethamine (SP) was combined with the 4-aminoquinolines as the first line treatment for falciparum malaria since 2000. To assess how this change had affected SP resistant gene polymorphisms, we determined allele frequencies of
dhfr and
dhps in 113
Plasmodium falciparum isolates from Wewak, East Sepik of Papua New Guinea in 2002 and 2003. In
dhfr, double mutant (ACN
RNVI) was the predominant allele with a prevalence of 91%. We found a significant decrease of wild
dhfr allele prevalence (7%) compared with that reported in the adjacent area of East Sepik called the Wosera region (57%), before the drug policy changed in 1990–1993. Between 2002 and 2003, the prevalence of this allele decreased from 15% to 3% (
P
=
0.02). Two distinct microsatellite haplotypes flanking
dhfr were found in isolates with
dhfr double mutant, suggesting the selection of preexisting SP resistant parasites rather than a frequent occurrence of
dhfr mutations. The
dhfr/
dhps quartet mutations (ACN
RNVI in
dhfr and S
GEAA in
dhps) were identified in six of the isolates (8%) from 2003. This genotype, which is associated with in vivo resistance to SP, has not been reported before in Papua New Guinea. These findings suggest that isolates resistant to SP were rapidly selected despite the use of the SP combination therapy, probably because of their preexisting high level of resistance to the 4-aminoquinoline partner drug.