TABLE 2.

Survival of DSM1-resistant cell lines after exposure to lethal atovaquone concentrations^a

Condition	Average % survivalb (range of days to detectionc) of clonal population:
	Dd2	C12	C53-1	C710-2a
1-day exposure, 10 nM ATOd	0 (NAe)	14 (16–18)	86 (9–13)	88 (11–13)
5-day exposure, 10 nM ATO	0 (NA)	0	29 (21)	63 (16–18)
1-day exposure, 100 nM ATO	0 (NA)	0	57 (25–28)	38 (23–25)
5-day exposure, 100 nM ATO	0 (NA)	0	14 (34)	25 (30–37)

^aThis method is derived from our earlier work (11). Starting from freshly thawed parasites of low parasitemia, serial dilutions were performed to isolate clonal populations. Triplicate T25 flasks were seeded with 10 asynchronous infected erythrocytes and incubated for 1 or 5 days with solvent only (control) or 10 nM or 100 nM atovaquone (tests). Each culture was treated at approximately the same time, and at the end of incubation, the erythrocyte pellets were washed three times with complete medium and transferred to 24 wells of a flat-bottom 96-well plate. The plated cultures were grown in inhibitor-free medium under standard culture conditions with three medium changes per week out to 60 days. Viable populations were identified using flow cytometry-detected SYBR green fluorescence after each medium change.

^bAverage % survival = 100 × (average positive wells [test] ÷ average positive wells [control]).

^cRecovered parasites were observable around the same time as the solvent-only controls (our unpublished data).

^dATO, atovaquone.

^eNA, not applicable.