Case #280 – July, 2010

A 35-year-old woman went to her health care provider with complaints of abdominal pain, cramps and diarrhea. She told her doctor that she had recently returned from a business trip to Mexico. Stool was collected in 10% formalin and polyvinyl alcohol (PVA) for routine ova-and-parasite (O&P) examination. Figures A–D show what was observed at 1000x magnification on a trichrome-stained slide made from the PVA-preserved stool. The objects of interest measured on average 15-17 micrometers in diameter. What is your diagnosis? Based on what criteria?

Figure A

Figure B

Figure C

Figure D

This case showed cysts of Entamoeba coli, an intestinal amoeba generally considered nonpathogenic. Diagnostic morphologic features included:

cysts within the size range for E. coli (10-35 micrometers in diameter).
more than four nuclei per cyst (Figures B, C, and D).
nuclei containing coarse, clumped peripheral chromatin.