Molecular Analysis of Chloroquine and Sulfadoxine/Pyrimethamine Resistant Markers in Plasmodium Falciparum Isolated from Three Provinces in Southern Thailand

Objective: This study investigated mutations in various genes associated with chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) resistance in P. falciparum; including the P. falciparum chloroquine resistance transporter (pfcrt), P. falciparum multidrug resistance 1 (pfmdr1), P. falciparum dihydrofolate reductase (pfdhfr), and P. falciparum dihydropteroate synthase (pfdhps).Material and Methods: A total of 104 P. falciparum samples were obtained from patients across three (Ranong, Surat Thani and Yala) provinces of southern Thailand; between 2012 and 2019. To assess the genetic polymorphisms, pfcrt K76T and pfmdr1 N86Y were identified using PCR-RFLP assay, and pfdhfr C59R and pfdhps K540E was identified using Semi-nested PCR and nucleotide sequencing.Results: Genetic analysis revealed that 61 (58.65%) isolates were positive for pfcrt and 55 (52.88%) for pfmdr1. Notably, the Ranong province isolates showed high prevalence of pfdhfr 51I, 59R, 108N, and 164L mutations (IRN-L) along with pfdhps 540E mutation. The Surat Thani province isolates exhibited the highest frequency of quadruple mutations in both pfdhfr and pfdhps genes. Conclusion: The surveillance guidelines and policy formulation of appropriate Malaria treatment strategies must be implemented in these locations.