Oocysts with two sporocysts or individual sporocysts in human feces are diagnostic of intestinal infection. These first appear 14 to 18 days after ingesting beef ( S. hominis ), and 11 to 13 days after ingesting pork ( S. suihominis ). Flotation based on high-density solutions incorporating sodium chloride, cesium chloride, zinc sulfate, sucrose, Percoll, Ficoll-Hypaque or other such density gradient media is preferred to formalin-ethyl acetate or other sedimentation methods. Sporocysts of S. hominis average by micrometres and those of S. suihominis average by micrometres. Because of the overlap in size, size alone is not reliable as a diagnostic criterion of the species. Confirmatory staining with the periodic acid-Schiff (PAS) can be performed as the walls stain positively. PCR amplification of the rRNA may also be used.