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Presentation of Quiz #75

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A 58-year-old female kidney transplant patient presented with prolonged diarrhea.  She had no travel history and no other relevant symptoms.  On submission of fecal specimens for a routine Ova and Parasite examination, the fecal concentration was negative and the following images were seen from the trichrome-stained smear.


quiz75_slide1quiz75_slide2   
 

  • Are these images positive or negative for parasites?
  • What additional tests should be performed?  Why or why not?
  • Based on additional testing, what do you suspect as the causative agent?

Scroll Down for Answer and Discussion

 

 

 

Answer and Discussion of Quiz #75

Laboratory results of the O&P examinations were negative for three stools; however, the patient remained symptomatic and other diagnostic tests were ordered, including modified acid-fast stains for the coccidia (image on the left) and modified trichrome stains for microsporidia (1-2).  The following images were seen.

quiz75_slide3quiz75_slide4
 
Diagnosis

Based on these findings, the patient was diagnosed with Cryptosporidium spp. and microsporidian spores.  The oocysts in the image on the left measure 4-6 µm, and some sporozoites within the oocyst wall are visible.  Also, these Cryptosporidium spp. oocysts are modified acid-fast positive, as seen on the left.  Microsporidian spores cannot be differentiated to genus/species on the basis of the modified trichrome stain seen in the right image.  These organisms are now classified with the fungi, and the spores measure approximately 1.5-2.5 µm.  The diagnostic characteristic is the cross line or lateral line that represents the polar tubule.  Some of these structures can be seen in the spores on the right - note the pink structures that can mimic bacteria and/or small yeast forms.

Discussion

In the immunocompromised host, microsporidial infection may lead to overwhelming disease and death. The first cases of human microsporidiosis were identified in children with impaired immune systems, and infections have been widely recognized and studied in individuals with AIDS, primarily those with fewer than 100 CD41 T lymphocytes. Infection has also been recognized in organ transplant recipients who are intentionally immunosuppressed before and after transplantation; cases involve pediatric and adult kidney and liver transplant recipients, as well as those receiving bone marrow, lung, or heart-lung transplants.  Microsporidiosis should always be considered in the differential diagnosis for a wide range of clinical syndromes in immunocompetent, as well as immunocompromised individuals.

Certainly this patient is a likely candidate for a microsporidial infection.  Although dual infections with Cryptosporidium spp. and the microsporidia are uncommon, it is certainly possible and has been documented.  Recently, a new and highly divergent Enterocytozoon bieneusi genotype has been discovered in a human host (renal transplant patient); this genotype can be grouped with an equid species (3).  Although the patient became sick 7 years post-transplantation, symptoms began soon after contact with water contaminated with horse stool.  These findings should be taken into account for the management of immunocompromised patients such as HIV-infected patients and solid-organ transplant recipients. In these types of high-risk patients, they should be advised to avoid close contact with animals and follow prophylactic measures that may prevent infection.

References:

1.        Garcia, L.S. 2016. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.

2.         Garcia, L.S., R.Y. Shimizu, and D.A. Bruckner. 1994. Detection of Microsporidial Spores in Fecal Specimens from Patients Diagnosed with Cryptosporidiosis. J. Clin. Microbiol. 32:1739-1741.

3.         Pomares, C, M Santin, M Miegeville, A Espern, L Albano, P Marty, F Morio. 2012. A new and highly divergent Enterocytozoon bieneusi genotype isolated from a renal transplant recipient.  J Clin Microbiol 50:2176-2178.