Sunday, August 21, 2016

Answer to Case 410

Welcome to my new readers!

The answer to Case 410 is amebic keratitis due to Acanthamoeba sp.

As several of you mentioned, this organism can be identified by the presence of both trophozoites and cysts in the patient's specimen, as well as the characteristic source (ocular/contact lens) and exposure history (swimming in fresh water). Both Acanthamoeba spp. and Balamuthia mandrillaris form cysts and trophozoites in humans, whereas Naegleria fowleri only forms trophozoites (and rarely flagellated forms in cerebrospinal fluid), and therefore the latter can be excluded by the presence of the cyst forms. Of the two organisms that do form cysts in humans, only Acanthamoeba species are known to cause ocular infections - primarily in patients who wear contact lenses, thus giving us our final diagnosis.


Acanthamoeba are free-living amebae that are ubiquitous in fresh water sources and can therefore easily contaminate contact lenses when worn during swimming. Note that there are also abundant bacteria present in this specimen. The bacteria that grew in the routine cultures from this patient were also common environmental organisms, and it is therefore they also likely were introduced while he was swimming with his contact lenses.


Mercedes said...

Please I soul de like to know W hice Kind of satinado is this and What dilution, Thank You so much,

Mercedes said...

Excuse me , Please I would like to know which kind of stain is this and What is dilution?
Thank you so much,

ParasiteGal said...

This is a hematoxylin and eosin stain - a stain commonly used in histopathologic sections. The specimen is ocular fluid that was spun down and made into a cell block which was embedded in paraffin and sectioned like a tissue.