Plasmodium falciparum with Multidrug Resistance 1 Gene Duplications, Senegal

To the Editor: Amplification and overexpression of the Plasmo-dium falciparum multidrug resistance 1 gene (Pfmdr1) have been associated with mefloquine resistance in P. Another isolate was obtained in a patient from Benin who did not respond clinically to mefloquine treatment (8). Pfmdr1 amplification has not been found in samples collected either before or after treatment for recurring P. falciparum infection in Africa in many studies. In Dakar, Senegal, and its surrounding suburbs, malaria is transmitted with spatial heterogeneity to the human mosquito bite rate, which ranged from 0.1 to 250 bites per person per night during the rainy seasons of 2007–2010. P. falciparum isolates from patients with malaria who lived in Dakar (>80%) and the surrounding area and did not travel during the previous month were obtained during the patients, 38% female). Informed verbal consent from the patients and/or their parents/guardians was obtained before blood collection; the study was approved by the ethical committee of the Hôpital Principal de Dakar. Of the 301 patients, 54% were recruited from the emergency department during each of the 2 seasons; other patients were recruited from the intensive care unit (18% during Oc-pediatric department (9% and 5%), and other units (19% and 21%). No significant differences were found between the 2 seasons for parasitemia (p = 0.160), sex ratio (p = 0.446), living area (p = 0.651), or hospital admission status (p = 0.567). Information on an-timalarial treatment before admission was not available. We analyzed the Pfmdr1 copy number for the 301 isolates by using TaqMan real-time PCR as described (7); 167 isolates were successfully evaluated by using the 72-h histidine-rich protein 2 test as described (9). P. falciparum clones 3D7 (1 Pfmdr copy) and W2 (3 Pfmdr1 copies) were used as controls for the determination of the Pfmdr1 copy number and for the validation of the batches of plates used in the susceptibility tests. A total of 9 isolates with 2 Pfmdr1 copies were identified, 1 collected during the 2009–2010 season and 8 collected during the 2010–2011 season. This finding reflects a statistically significant 10-fold increase in frequency of isolates from 1 season to the next (p = 0.0057 by Fisher exact test). All of the isolates with duplicated copies had 1 allelic family for each of the 3 genes (msp1, msp2, and glurp), confirming that these infections were single and not mixed. We did not find an association between Pfmdr1 copy number …