TABLE 1.

In vitro drug susceptibility profiles of the day 0 and day 49 parasites^a

Sample	Date of collection	Parasitemia	IC₅₀ (nmol/liter) for drug
Sample	Date of collection	Parasitemia	Chloroquine	Quinine	Mefloquine	Halofantrine	b-Artemether	Atovaquone
Day 0	14 February 2005	2	116	83	14.2	8.7	1.3	1.6
Day 49	04 April 2005	1	111	364	21	3.4	2.7	20.5

Drug assays were performed at a 1% hematocrit over a 48-h culture period using the ³H-hypoxanthine incorporation microtest (6). Each isolate was tested once in duplicate against serial twofold dilutions of antimalarials over the following concentration ranges: 5,120 to 5 nM for chloroquine (chloroquine diphosphate; Sigma; catalog no. C6628), 6,400 to 6.2 nM for quinine (quinine sulfate; Sigma; catalog no. Q1878), 1,024 to 1 nM for mefloquine (Hoffman-La Roche, Inc.), 25.6 to 0.025 nM for halofantrine (GlaxoSmithKline, Inc.), and 200 to 0.19 nM for artemether (Novartis Pharma, Inc.) and atovaquone (GlaxoSmithKline, Inc.). The IC₅₀ was calculated using probit/log regression of the percent growth inhibition for each drug.