Plasmodium falciparum chloroquine-resistance transporter gene detection in imported Plasmodium falciparum malaria cases.

To the Editor—We share the cogent sentiments expressed by Farcas et al. [1] about the great interest of PCR-based methods for the diagnosis of imported malaria, given that, in most westernized countries, morbidity and death due to this protozoan infection among returned travelers is on the rise [2]. Because we have tested 1900 patients per year since Octo-ber 1999, we have accumulated a large amount of routine experience in the molecular diagnosis of imported malaria. First using conventional PCR [3], and now using real-time PCR [4], we have found that the detection of mixed-species infections was sharply improved by both techniques. Overall, however, real-time PCR demonstrates a decisive feature for our cli-nician colleagues: the capacity to ensure, in a turnaround time of !4 hours, 6 days a week, that a given febrile traveler does not have malaria. In addition to its utility in the diagnosis of malarial infection, PCR appeared to be a must for epidemiological surveys fo-cused on Plasmodium falciparum with resistance to aminoquinolines, as assessed by the detection of point mutations in the P. falciparum chloroquine-resistance transporter (pfcrt) and P. falciparum multidrug-resistance (pfmdr1) genes. Performed in cohorts of returned travelers or immigrants , such molecular surveillance studies showed that a large proportion of patients (1%–3%) who presented with falciparum malaria harbored the K76 (wild-type) P. falciparum strain [5, 6]. In other words, the malarial infections of these subjects probably would have been cured by chlo-roquine (CQ), which remains one of the cheapest and safest drugs ever used for malaria treatment. So, we are in full agreement with Farcas et al. [1], who claimed that the molecular assessment of CQ sensitivity , based on the detection of T76 mutation by real-time PCR, appeared to offer an interesting perspective, as previously suggested in a review article [7]. In this view, the sensitivity of a molecular test for the detection of CQ resistance would be of crucial importance. That is, such an assay should display good absolute sensitivity, but it should also be able to detect a minority mutant fraction in a sensitive wild-type population. The test performed by Vessiére et al. [8] in the Department of Parasitology (Rangueil University Hospital, Toulouse, France) exhibited 2% sensitivity for the detection of the K76T mutation, which appeared to be insufficient to avoid the occurrence of RI/ RII resistance in the event of therapeutic use of CQ. We therefore developed a more sophisticated assay, …