Identification of molecular markers of Plasmodium falciparum resistance to antifolates by PCR and sequencing in the Republic of Guinea

Introduction: Malaria remains one of the leading causes of medical consultations in the tropics.  Objective: The aim of this study was to determine the types of mutations responsible for Plasmodium falciparum resistance to antifolates in Guinea. Material and Methods: This is a prospective study lasting eight (8) months, from October 1, 2022, to May 30, 2023.

RESULTS:  The diagnosis of Plasmodium falciparum was positive in 5.85% of cases (255/4352) by thick blood smear (SBS) and and the thin blood smear. The molecular method (PCR) applied to the 255 SBS-positive samples showed the presence of Plasmodium falciparum DNA was positive in 96.47% of the SBS-positive samples (246/255). In individuals over 5 years of age, mutations were higher in the Pfdhfr gene at codons 51Ile, 59Arg and 108Asn with a prevalence of 28.57% for each. On the contrary, in the Pfdhps gene, the highest mutation was in codon 540Glu (5.71%) followed by mutations 436Ala, 437Gly and 613Ser with 2.85% for each. In children under 5 years of age, mutations were more common in the pfdhfr gene codons: 51Ile (42.85%), 59Arg (42.85) and 108Asn (42.85), while in the Pfdhps gene, mutations were common in codon 540Glu (5.71%), followed by codons 436Ala, 437Gly and 613Ser with 2.85% each. Thus, mutations were more common in the Pfdhfr gene than in the Pfdhps gene. After sequencing, only 14.22% (35/246) Plasmodium falciparum samples had mutations in both Pfdhfr and Pfdhps.

Conclusion: These results showed generally that mutations in Plasmodium falciparum resistance genes, were more common in dhfr gene than dhps gene and the mutation prevalence of these two genes were different i individuals over 5 yeares and those of under 5 years.