Figure. Top, agarose gel electrophoresis of nested PCR products of human fecal samples amplified with primers (pairs DW2-F + DW2-R and CYTB1-F + CYTB2-R) and stained with ethidium bromide. Bottom, autoradiograph of a Southern blot of the same gel. α-32P-ATP–labeled acytochrome B gene of Plasmodium falciparum was used as a probe. Lanes 1–6, samples from humans with malaria (the infection sample in lane 6 is weak); lane 2, spurious amplicon; lane 7, sample from an uninfected person; lane M, 1-kb molecular mass (Invitrogen, Carlsbad, CA, USA).