{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,20]],"date-time":"2026-02-20T08:54:05Z","timestamp":1771577645309,"version":"3.50.1"},"reference-count":27,"publisher":"Springer Science and Business Media LLC","issue":"1","content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["Malar J"],"published-print":{"date-parts":[[2013,12]]},"abstract":"<jats:title>Abstract<\/jats:title>\n          <jats:sec>\n            <jats:title>Background<\/jats:title>\n            <jats:p>Chloroquine (CQ) and primaquine (PQ) are still the drugs of choice to treat <jats:italic>Plasmodium vivax<\/jats:italic> malaria in many endemic areas, Brazil included. There is <jats:italic>in vivo<\/jats:italic> evidence for the <jats:italic>P. vivax<\/jats:italic> resistance to CQ in the Brazilian Amazon, where the increase in the proportion of <jats:italic>P. vivax<\/jats:italic> malaria parallels the increase of unusual clinical complications related to this species. In this study, <jats:italic>in vitro<\/jats:italic> CQ and mefloquine (MQ)-susceptibility of <jats:italic>P. vivax<\/jats:italic> isolates from the Western Brazilian Amazon was tested using the double-site enzyme-linked lactate dehydrogenase immunodetection (DELI) assay.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Methods<\/jats:title>\n            <jats:p>A total of 112 <jats:italic>P. vivax<\/jats:italic> isolates were tested <jats:italic>in vitro<\/jats:italic> for CQ-susceptibility and out of these 47 were also tested for MQ-susceptibility. The DELI assay was used to detect <jats:italic>P. vivax<\/jats:italic> growth at 48-hour short-term culture in isolates with ring stages ranging from 50 to %. Each isolate was tested in triplicate and geometric means of IC50\u2019s was obtained. Nineteen isolates were genetically characterized for <jats:italic>pvdhfr, pvmrp1, pvmdr1<\/jats:italic> and <jats:italic>pvdhps<\/jats:italic> candidate genes likely related to CQ resistance (10 with IC50&lt;40 nM and 9 with IC50 &gt;100 nM).<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Results<\/jats:title>\n            <jats:p>Twelve out of 112 isolates were considered resistant to CQ, resulting in 10.7% (IC95% 5.0-16.4), while 3 out of 47 (6.4%; IC95% 0.0-12.8) were resistant to MQ. A discrete correlation was observed between IC50\u2019s of CQ and MQ (Spearman=0.294; p=0.045). For <jats:italic>pvdhps<\/jats:italic> gene, a non-synonymous mutation was found at codon 382 (S\u2192C) in 5\/8 CQ-sensitive samples and 1\/9 CQ-resistant samples (p=0.027). The other molecular markers were not associated to CQ-susceptibility.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Conclusions<\/jats:title>\n            <jats:p>\n              <jats:italic>In vitro<\/jats:italic> CQ-resistance estimated in this study, estimated by the DELI test, was very similar to that observed in clinical trials, suggesting that <jats:italic>in vitro<\/jats:italic> procedures developed by capable local laboratories are useful in the surveillance of CQ-resistance in the Amazon; concurrent Amazon <jats:italic>P. vivax<\/jats:italic> strains with both CQ and MQ resistance may be common; and a non-synonymous mutation at <jats:italic>pvdhps<\/jats:italic> codon 382 (S\u2192C) was associated to <jats:italic>in vitro<\/jats:italic> susceptibility to CQ, needing further studies to be confirmed.<\/jats:p>\n          <\/jats:sec>","DOI":"10.1186\/1475-2875-12-226","type":"journal-article","created":{"date-parts":[[2013,7,3]],"date-time":"2013-07-03T02:26:21Z","timestamp":1372818381000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":35,"title":["In vitro chloroquine resistance for Plasmodium vivax isolates from the Western Brazilian Amazon"],"prefix":"10.1186","volume":"12","author":[{"given":"Yonne F","family":"Chehuan","sequence":"first","affiliation":[]},{"given":"Monica RF","family":"Costa","sequence":"additional","affiliation":[]},{"given":"Jacqueline S","family":"Costa","sequence":"additional","affiliation":[]},{"given":"Maria GC","family":"Alecrim","sequence":"additional","affiliation":[]},{"given":"F\u00e1tima","family":"Nogueira","sequence":"additional","affiliation":[]},{"given":"Henrique","family":"Silveira","sequence":"additional","affiliation":[]},{"given":"Larissa W","family":"Brasil","sequence":"additional","affiliation":[]},{"given":"Gisely C","family":"Melo","sequence":"additional","affiliation":[]},{"given":"Wuelton M","family":"Monteiro","sequence":"additional","affiliation":[]},{"given":"Marcus VG","family":"Lacerda","sequence":"additional","affiliation":[]}],"member":"297","published-online":{"date-parts":[[2013,7,3]]},"reference":[{"key":"2838_CR1","doi-asserted-by":"publisher","first-page":"e774","DOI":"10.1371\/journal.pntd.0000774","volume":"4","author":"CA Guerra","year":"2010","unstructured":"Guerra CA, Howes RE, Patil AP, Gething PW, Van Boeckel TP, Temperley WH, Kabaria CW, Tatem AJ, Manh BH, Elyazar IR, Baird JK, Snow RW, Hay SI: The international limits and population at risk of Plasmodium vivax transmission in 2009. 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