title: Polymorphism in drug resistance genes dihydrofolate reductase and dihydropteroate synthase in Plasmodium falciparum in some states of India.
abstract: BACKGROUND
  Sulfadoxine-pyrimethamine (SP) combination drug is currently being used in India for the treatment of Plasmodium falciparum as partner drug in artemisinin-based combination therapy (ACT). Resistance to sulfadoxine and pyrimethamine in P. falciparum is linked with mutations in dihydropteroate synthase (pfdhps) and dihydrofolate reductase (pfdhfr) genes respectively. This study was undertaken to estimate the prevalence of such mutations in pfdhfr and pfdhps genes in four states of India.
  
  
  METHODS
  Plasmodium falciparum isolates were collected from two states of India with high malaria incidence i.e., Jharkhand and Odisha and two states with low malaria incidence i.e., Andhra Pradesh and Uttar Pradesh between years 2006 to 2012. Part of sulfadoxine-pyrimethamine (SP) drug resistance genes, pfdhfr and pfdhps were PCR-amplified, sequenced and analyzed.
  
  
  RESULTS
  A total of 217 confirmed P. falciparum isolates were sequenced for both Pfdhfr and pfdhps gene. Two pfdhfr mutations 59R and 108N were most common mutations prevalent in all localities in 77 % of isolates. Additionally, I164L was found in Odisha and Jharkhand only (4/70 and 8/84, respectively). Another mutation 51I was found in Odisha only (3/70). The pfdhps mutations 436A, 437G, 540E and 581G were found in Jharkhand and Odisha only in 13, 26, 14 and 13 % isolates respectively, and was absent in Uttar Pradesh and Andhra Pradesh. Combined together for pfdhps and pfdhfr locus, triple, quadruple, quintuple and sextuple mutations were present in Jharkhand and Odisha while absent in Uttar Pradesh and Andhra Pradesh.
  
  
  CONCLUSIONS
  While only double mutants of pfdhfr was present in low transmission area (Uttar Pradesh and Andhra Pradesh) with total absence of pfdhps mutants, up to sextuple mutations were present in high transmission areas (Odisha and Jharkhand) for both the genes combined. Presence of multiple mutations in pfdhfr and pfdhps genes linked to SP resistance in high transmission area may lead to fixation of multiple mutations in presence of high drug pressure and high recombination rate.
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi-110077, India. sharma5divya@gmail.com.
authors.forename: Divya
authors.initials: D
authors.lastname: Sharma
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi-110077, India. manila.lather@gmail.com.
authors.forename: Manila
authors.initials: M
authors.lastname: Lather
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi-110077, India. pkmmrc@gmail.com.
authors.forename: Prashant K
authors.initials: PK
authors.lastname: Mallick
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi-110077, India. adak.mrc@gmail.com.
authors.forename: Tridibes
authors.initials: T
authors.lastname: Adak
authors.affiliation: Centre for Medical Biotechnology, Maharshi Dayanand University, Rohtak, 124001, India. suneja_a@yahoo.co.in.
authors.forename: Amita S
authors.initials: AS
authors.lastname: Dang
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi-110077, India. neenavalecha@gmail.com.
authors.forename: Neena
authors.initials: N
authors.lastname: Valecha
authors.affiliation: National Institute of Malaria Research, Sector 8, Dwarka, Delhi-110077, India. singh@mrcindia.org.
authors.forename: Om P
authors.initials: OP
authors.lastname: Singh
mesh_terms: D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004094:Dihydropteroate Synthase / Q000235:genetics*; D004351:Drug Resistance; D007194:India; D016778:Malaria, Falciparum / Q000469:parasitology; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010963:Plasmodium falciparum / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*
chemical_list: D016054:DNA, Protozoan; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase