TABLE 5.
Comparison of ex vivo chloroquine resistance data currently available for Plasmodium vivax isolates from South America
| Reference | Yr of collection | Site, country | No. of samples | IC50 for chloroquine (nM) estimated by P. vivax schizont maturation test |
% of isolates with IC50 > 100 nM (95% CI) | ||
|---|---|---|---|---|---|---|---|
| Geometric mean | Median | Range | |||||
| 27 | 2004–2007 | Manaus, Brazil | 132a ,b | 24.1 | 5–729 | 9.8 (5.6–16.6) | |
| 26 | 2007–2008 | Manaus, Brazil | 112a ,b | ∼8–500 | 10.7 (5.9–18.3) | ||
| 25 | 2010–2012 | Urabá, Colombia | 30b ,c | 23.3 | 2.5–1,109.0 | 13.3 (4.4–31.6) | |
| 24 | 2012–2013 | Porto Velho, Brazil | 32b ,c | 32 | 3–69 | 0.0 (0.0–13.3) | |
| Present study | 2014–2017 | Mâncio Lima, Brazil | 49c ,d | 15.8 | 17.4 | 4.1–63.3 | 0.0 (0.0–9.1) |
a
Parasite density assessed by double-site enzyme-linked immunodetection (DELI) test.
b
Assays carried out with fresh isolates.
c
Parasite density and staging assessed by microscopy.
d
Assays carried out with cryopreserved isolates. Forty of 128 (31.2%) cryopreserved P. vivax isolates from participants in the clinical trial had IC50 estimates determined; a further 9 isolates from subjects who did not participate in the clinical trial but were living in the same area were successfully tested, giving a total of 49 local samples analyzed.