title: In vitro susceptibility of Plasmodium falciparum isolates to chloroquine and mefloquine in southeastern Mindanao Island, the Philippines.
abstract: Although the presence of multi-drug-resistant falciparum malaria has been reported in the Philippines, the distribution of drug-resistant malaria parasites has not yet been determined in Mindanao Island. In vitro susceptibility of P. falciparum to both chloroquine and mefloquine was assessed to forecast the spread of drug-resistant parasites in various foci in southeastern Mindanao Island. Of the 33 isolates of P. falciparum successfully tested, 10 (30%) were susceptible, 12 (36%) showed decreased susceptibility (80 nM < or = IC50 < 114 nM), and 11 (33%) were resistant (IC50 > or = 114 nM) to chloroquine. Ten (91%) of the resistant isolates and 9 (75%) of those with decreased susceptibility were from northern and northwestern Davao del Norte Province. Chloroquine-susceptible isolates were found among patients in the eastern parts of Davao del Norte and Davao Oriental provinces. Seven isolates from several foci in the study area were all mefloquine- susceptible (IC50 < 10 nM). This is the first report indicating the potential emergence of chloroquine-resistant P. falciparum on Mindanao Island, which is presently regarded as a drug-susceptible area.
authors.affiliation: International Medical Center of Japan, Tokyo, Japan.
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Hatabu
authors.forename: Shin-ichiro
authors.initials: S
authors.lastname: Kawazu
authors.forename: Jun
authors.initials: J
authors.lastname: Suzuki
authors.forename: Reuben F
authors.initials: RF
authors.lastname: Valenzuela
authors.forename: Elena A
authors.initials: EA
authors.lastname: Villacorte
authors.forename: Mamoru
authors.initials: M
authors.lastname: Suzuki
authors.forename: Pilarita T
authors.initials: PT
authors.lastname: Rivera
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Kano
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D002738:Chloroquine / Q000494:pharmacology*; D018432:Drug Resistance, Multiple; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D016778:Malaria, Falciparum / Q000188:drug therapy / Q000453:epidemiology; D008297:Male; D015767:Mefloquine / Q000494:pharmacology*; D021261:Parasitic Sensitivity Tests; D010679:Philippines / Q000453:epidemiology; D010963:Plasmodium falciparum / Q000187:drug effects*; D012111:Residence Characteristics
chemical_list: D000962:Antimalarials; D002738:Chloroquine; D015767:Mefloquine