A state health laboratory received stool specimens collected in in sodium acetat

Question

A state health laboratory received stool specimens collected in in sodium acetate-acetic acid-formalin (SAF) for ova-and-parasite (O&P;) examination. The patient was an immigrant, but his specific country of origin was not known. The stool was processed by formalin-ethyl acetate (FEA) concentration and trichrome staining. The attending microbiologist observed what she believed to be trophozoites of an Entamoeba species in both the wet mount from the FEA and the trichrome-stained smear, no cysts were observed. Digital images of the suspect amoebac were captured and sent to the DPDx Team for diagnostic assistance. Figure A shows what was observed in an unstained wet mount of the FEA concentrate; Figure B is also from the wet mount, but stained with iodine. Figures C and D show what was observed on the trichrome-stained slide 1. What is your diagnosis? 2. Based on what criteria? 3. What is a alternative that you considered, but discounted?

Explanation / Answer

This patient is suffering from the Amebiasis caused by the Entamoeba histolytica

Entamoeba histolytica is well recognized as a pathogenic ameba, associated with intestinal and extraintestinal infections.

Because given slides showing trophozoites of Entamoeba histolytica.

Diagnostic morphologic features included:

·         trophozoites within the size range of Entamoeba histolytica/dispar .

·         a single nucleus with evenly-distributed peripheral chromatin and a discrete karyosome that is centrally (or slightly eccentrically) located.

I am considering the giardiasis alternatively

Entamoeba histolytica, Giardia. Yes these organisms are pathogenic

This is a case of invasive amebiasis caused by Entamoeba histolytica.

because

·         trophozoites with a single nucleus containing even peripheral chromatin and ingested red blood cells.

·         a size range consistent with E. histolytica versus white blood

Serology is a useful tool to aid in the diagnosis of invasive or extraintestinal amebiasis prior to the use of invasive techniques.

alternative diagnosis is bacterial dysentery, or shigelosis

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