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Background   Plasmodium vivax  is the most widely distributed species causing the highest number of malaria cases in the world. In Brazil,  P. vivax  is responsible for approximately 84 % of reported cases. In the absence of a vaccine, control strategies are based on the management of cases through rapid diagnosis and adequate treatment, in addition to vector control measures. The approaches used to investigate  P. vivax  resistance to chloroquine (CQ) were exclusively in vivo studies because of the difficulty in keeping parasites in continuous in vitro culture. In view of the limitations related to follow-up of patients and to assessing the plasma dosage of CQ and its metabolites, an alternative approach to monitor chemo-resistance (QR) is to use molecular markers. Single nucleotide polymorphisms (SNPs) in the multidrug resistance gene  pvmdr1  are putative determinants of CQ resistance (CQR), but such SNPs in  P. vivax  isolates from patients with good response to treatment should be further explored. The aim of this study is to investigate the mutations in the gene, supposedly associated to QR, in  P. vivax  isolates from successfully cured patients, living in Brazilian endemic and non-endemic areas.    Methods  Blood samples were collected from 49 vivax malaria patients from endemic (Amazon Basin: 45) and non-endemic (Atlantic Forest: four) Brazilian regions and analysed for SNPs in the CQR-related  P. vivax  gene ( pvmdr1 ), using PCR-based methods.    Results  Among the 49 isolates genetically characterized for the gene  pvmdr1 , 34 (70 %) presented at least one mutation. T958 M  mutant alleles were the most frequent (73 %) followed Y976 F  (15 %) and F1076 L  (12 %). Single mutation was detected in 24 (70.5 %) isolates and double mutations in ten (29.5 %). The most common single mutant genotype was the 958 M/ Y976/F1076 (79 %), followed by 976 F/ F1076 (21 %) whereas 958 M/ Y976/1076 L  (60 %) and 976 F/ 1076 L  (40 %) double mutant genotypes were detected. Single mutant profile was observed only in isolates from Amazon Basin, although double mutants were found both in the Amazon and Atlantic Forest regions. Interestingly, the genotype 958 M /Y976/1076 L  was present in all isolates from the Atlantic Forest in the Rio de Janeiro State.    Conclusions  Considering that primaquine (PQ) efficacy is highly dependent on concurrent administration of a blood schizontocidal agent and that PQ could not circumvent CQR, together with the fact that no  pvmdr1  mutation should be expected in successfully cured patients, these findings seem to indicate that the  pvmdr1  gene is not a reliable marker of CQR. Further investigations are needed to define a reliable molecular marker for monitoring  P. vivax  CQR in  P. vivax  populations.

Plasmodium vivax mdr1 genotypes in isolates from successfully cured patients living in endemic and non-endemic Brazilian areas