Journal
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY
Volume 61, Issue 8, Pages -Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/AAC.00355-17
Keywords
malaria; Plasmodium falciparum; Plasmodium vivax; drug resistance; chloroquine; chloroquine resistance reversal
Categories
Funding
- Wellcome Trust [200909, 099875]
- National Health and Medical Research Council [1023438, 1037304]
- Swiss National Science Foundation [PA00P3_134195/1]
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High-grade chloroquine (CQ) resistance has emerged in both Plasmodium falciparum and P. vivax. The aim of the present study was to investigate the phenotypic differences of CQ resistance in both of these species and the ability of known CQ resistance reversal agents (CQRRAs) to alter CQ susceptibility. Between April 2015 and April 2016, the potential of verapamil (VP), mibefradil (MF), L703,606 (L7), and primaquine (PQ) to reverse CQ resistance was assessed in 46 P. falciparum and 34 P. vivax clinical isolates in Papua, Indonesia, where CQ resistance is present in both species, using a modified schizont maturation assay. In P. falciparum, CQ 50% inhibitory concentrations (IC(50)s) were reduced when CQ was combined with VP (1.4-fold), MF (1.2-fold), L7 (4.2-fold), or PQ (1.8-fold). The degree of CQ resistance reversal in P. falciparum was highly correlated with CQ susceptibility for all CQRRAs (R-2 = 0.951, 0.852, 0.962, and 0.901 for VP, MF, L7, and PQ, respectively), in line with observations in P. falciparum laboratory strains. In contrast, no reduction in the CQ IC(50)s was observed with any of the CQRRAs in P. vivax, even in those isolates with high chloroquine IC(50)s. The differential effect of CQRRAs in P. falciparum and P. vivax suggests significant differences in CQ kinetics and, potentially, the likely mechanism of CQ resistance between these two species.
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