Chloroquine-resistant Plasmodium falciparum isolates from the Sudan lack two mutations in the pfmdr1 gene thought to be associated with chloroquine resistance.

Isolates of Plasmodium falciparum from 3 areas of the Sudan were recovered from cryopreservation in London and their chloroquine sensitivity was determined in vitro. Chloroquine resistance was detected in 6/6 isolates from Khartoum, 1/4 from Sennar and 3/3 from Gadarif, indicating that resistance is spreading. All the isolates were sensitive to mefloquine. Studies using blood spots on glass fibre discs and the polymerase chain reaction did not detect two mutations in the pfmdr1 gene, thought to be correlated with chloroquine-resistance, in any of the isolates studied.