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<jats:title>ABSTRACT</jats:title><jats:p>The 4-aminoquinoline naphthoquine (NQ) and the thiazine dye methylene blue (MB) have potent<jats:italic>in vitro</jats:italic>efficacies against<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">Plasmodium falciparum</jats:named-content>, but susceptibility data for<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. vivax</jats:named-content>are limited. The species- and stage-specific<jats:italic>ex vivo</jats:italic>activities of NQ and MB were assessed using a modified schizont maturation assay on clinical field isolates from Papua, Indonesia, where multidrug-resistant<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. falciparum</jats:named-content>and<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. vivax</jats:named-content>are prevalent. Both compounds were highly active against<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. falciparum</jats:named-content>(median [range] 50% inhibitory concentration [IC<jats:sub>50</jats:sub>]: NQ, 8.0 nM [2.6 to 71.8 nM]; and MB, 1.6 nM [0.2 to 7.0 nM]) and<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. vivax</jats:named-content>(NQ, 7.8 nM [1.5 to 34.2 nM]; and MB, 1.2 nM [0.4 to 4.3 nM]). Stage-specific drug susceptibility assays revealed significantly greater IC<jats:sub>50</jats:sub>s in parasites exposed at the trophozoite stage than at the ring stage for NQ in<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. falciparum</jats:named-content>(26.5 versus 5.1 nM,<jats:italic>P</jats:italic>= 0.021) and<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. vivax</jats:named-content>(341.6 versus 6.5 nM,<jats:italic>P</jats:italic>= 0.021) and for MB in<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. vivax</jats:named-content>(10.1 versus 1.6 nM,<jats:italic>P</jats:italic>= 0.010). The excellent<jats:italic>ex vivo</jats:italic>activities of NQ and MB against both<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. falciparum</jats:named-content>and<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="genus-species" xlink:type="simple">P. vivax</jats:named-content>highlight their potential utility for the treatment of multidrug-resistant malaria in areas where both species are endemic.</jats:p>

Original publication

DOI

10.1128/aac.00874-15

Type

Journal article

Journal

Antimicrobial Agents and Chemotherapy

Publisher

American Society for Microbiology

Publication Date

10/2015

Volume

59

Pages

6117 - 6124