Answer: Presumed amebae; either non-pathogenic amebae from GI contamination or possible free-living organisms.
I posted this case because it was challenging for me as well and I wanted to see what the others had to say. Of the comments I received, the votes were as follows:
Amebae, (various types) - 8 votes
Chlamydia-infected epithelial cells - 1 vote
White blood cell, NOS - 1 vote
Trichomonas vaginalis - 2 votes
I was happy to see that the consensus supported my initial diagnosis. The features that I feel support the identification of ameba include the small size (< 10 microns in diameter), small nucleus (smaller than would be expected for an epithelial cell or macrophage) with large nucleolus/karyosome, and what appears to be phagocytosed material in the cytoplasm:
Thank you for writing in with your comments!