The frontline treatment for uncomplicated malaria in Western Cambodia is the drug combination dihydroartemisinin (DHA) – piperaquine (PPQ). In response to increasing reports that this treatment was failing in the region, researchers tested samples collected from three locations in Cambodia to investigate whether the parasites were becoming resistant to DHA, PPQ or both drugs. They tested these samples for known molecular markers and for susceptibility to six antimalarial drugs. They found no evidence of PPQ resistance, which suggests that DHA-PPQ treatment failures are the result of artemisinin resistance. In addition, they observed that parasites with multiple copies of the multidrug resistance gene pfmdr1 tended to be less susceptible to several drugs, including DHA.
Lim et al. Ex vivo susceptibility of Plasmodium falciparum to antimalarial drugs in western, northern, and eastern Cambodia, 2011-2012: association with molecular markers. Antimicrob Agents Chemother. 2013 Nov;57(11):5277-83. doi: 10.1128/AAC.00687-13. Epub 2013 Aug 12.