en انگل شناسي Parasitology پژوهشي Research <div style="text-align: justify;"><strong>Background: </strong>Antimalarial drug resistance is one of the important challenges for governments in the fight against malaria. Molecular surveillance of antimalarial drug resistance supports early detection of how the recommended treatments work. This allows immediate action to reduce any threat and prevent it from spreading. Therefore, the aim of this study was to evaluate the frequency of <em>dihydrofolate </em>reductase (<em>dhfr</em>) mutants in <em>Plasmodium falciparum</em> resistance to pyrimethamine in Iranian malaria patients.</div> <div style="text-align: justify;"><strong>Materials and Methods:</strong> In 2020, 27 patients (21 males and 5 females) with imported <em>P. falciparum</em> cases were studied. The nested-PCR technique first confirmed the species in all samples and then amplification was done by the semi-nested-PCR method in order to detect single nucleotide polymorphisms (SNPs) in <em>dhfr </em>gene related to pyrimethamine resistance.</div> <div style="text-align: justify;"><strong>Results:</strong> All samples in the <em>18S</em> rRNA gene had species-specific bands for <em>P. falciparum</em> strains. In the sequence analysis of <em>pfdhfr </em>gene amplification after comparison with the standard strain (wild type), 21 patients had a double mutation (C59R+S108N) and six patients had a triple mutation (N51I+C59R+S108N) of pyrimethamine resistance.</div> <div style="text-align: justify;"><strong>Conclusion: </strong>The results of this study showed that the susceptibility of <em>P. falciparum</em> to pyrimethamine in the treatment of malaria is significantly reducing. These findings can raise concerns about pyrimethamine resistance in <em>P. falciparum</em>. Due to the high emergence of double and triple mutants related to pyrimethamine resistance, the malaria surveillance and treatment systems in Iran, the use of pyrimethamine should be considered.</div> Malaria, Plasmodium falciparum, drug resistance, pyrimethamine, pfdhfr, Iran 277 286 http://rmm.mazums.ac.ir/browse.php?a_code=A-10-1238-1&slc_lang=en&sid=1 Seyyed Ali Shariatzadeh a.shariatzade@yahoo.com 1 100319475328460010924 No 1Student Research Committee, Mazandaran University of Medical Science, Sari, Iran Reza Valadan rvaladan@mazums.ac.ir 2 100319475328460010925 No Molecular and Cell Biology Research Center (MCBRC), Mazandaran University of Medical Sciences, Sari, Iran Seyed Abdollah Hosseini hosseini4030@gmail.com 3 100319475328460010926 No Department of Parasitology, Faculty of Medicine, Mazandaran University of Medical Sciences, Sari, Iran Adel Spotin adelespotin@gmail.com 4 100319475328460010927 No Infectious and Tropical Diseases Research Center, Tabriz University of Medical Sciences, Tabriz, Iran Abbas Shahbazi Shahbazy42@yahoo.com 5 100319475328460010928 No Department of Parasitology and Mycology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran Davood Anvari davood_anvari@live.com 6 100319475328460010929 No School of Medicine, Iranshahr University of Medical Sciences, Iranshahr, Iran Fattaneh Montazeri Fattaneh.montazeri@yahoo.com 7 100319475328460010930 No Department of Parasitology, Faculty of Medical Sciences, Tarbiat Modarres University, Tehran, Iran Javad Javidnia javidniaj@gmail.com 8 100319475328460010931 No Student Research Committee, Mazandaran University of Medical Science, Sari, Iran Shirzad Gholami sgholami200@gmail.com 9 100319475328460010932 Yes Toxoplasmosis Research Center, Communicable Diseases Institute, Mazandaran University of Medical Sciences, Sari, Iran