Identification of pyrimethamine- and chloroquine-resistant Plasmodium falciparum in Africa between 1984 and 1998: genotyping of archive blood samples

• Published in: Malaria Journal
• Main Authors: Saito-Nakano Yumiko, Tanabe Kazuyuki, Mita Toshihiro
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2011
• Subjects: Plasmodium falciparum; Drug resistance; Chloroquine; pfcrt; Pyrimethamine; dhfr; Africa; Archive sample; Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic; Irni
• Online Access: https://doi.org/10.1186/1475-2875-10-388; https://doaj.org/article/110334dfc18942969f5b68231efd5b44

Abstract Background Understanding the geographical distribution of drug resistance of Plasmodium falciparum is important for the effective treatment of malaria. Drug resistance has previously been inferred mainly from records of clinical resistance. However, clinical resistance is not always consistent with the parasite's genetic resistance. Thus, molecular identification of the parasite's drug resistance is required. In Africa, clinical resistance to pyrimethamine (Pyr) and chloroquine (CQ) was evident before 1980 but few studies investigating the genetic resistance to these drugs were conducted before the late 1990s. In this study, genotyping of genes involved in resistance to Pyr and CQ was performed using archive blood samples from Africa between 1984 and 1998. Methods Parasite DNA was extracted from P. falciparum -infected blood smears collected from travellers returning to Japan from Africa between 1984 and 1998. Genotypes of the dihydrofolate reductase gene ( dhfr ) and CQ-resistance transporter gene ( pfcrt) were determined by polymerase chain reaction amplification and sequencing. Results Genotyping of dhfr and pfcrt was successful in 59 and 80 samples, respectively. One wild-type and seven mutant dhfr genotypes were identified. Three dhfr genotypes lacking the S108N mutation (NRSI, ICSI, IRSI; amino acids at positions 51, 59, 108, and 164 with mutations underlined) were highly prevalent before 1994 but reduced after 1995, accompanied by an increase in genotypes with the S108N mutation. The dhfr IRNI genotype was first identified in Nigeria in 1991 in the present samples, and its frequency gradually increased. However, two double mutants (ICNI and NRNI), the latter of which was exclusively found in West Africa, were more frequent than the IRNI genotype. Only two pfcrt genotypes were found, the wild-type and a Southeast Asian type (CVIET; amino acids at positions 72-76 with mutations underlined). The CVIET genotype was already present as early as 1984 in Tanzania and Nigeria, and appeared throughout ...