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Blastocystis hominis
Epidemiology:
- commonly found in stool specimens of asymptomatic individuals
- no significant difference in prevalence of Blastomyces in stool of patients with diarrhea vs those without diarrhea [2]
Pathology:
- protozoan that infests the colon
- heavy infestation may result in diarrhea or colitis
Clinical manifestations:
- intestinal
- abdominal pain, diarrhea, bloating, & flatulence
- extraintestinal manifestations are predominantly cutaneous [2]
Laboratory:
1) stool examination indicated only for patients with diarrhea lasting >= 3 days [2]
2) diagnosis is made by recovery of trophozoites in feces
3) trophozoites
a) 3 forms seen:
1] vacuolated (most common)
a] spherical 5-20 um in diameter
b] clear central area
c] 2-4 peripheral nuclei
2] amoeboid - may predominate in heavy infestations
3] granular
4) Blastocystis hominis DNA
Management:
1) therapy not uniformly effective
- asymptomatic patients do not require therapy [2,3]
2) metronidazole 750 mg PO TID for 10 days
3) Bactrim has been found to have activity against Blastomyces
4) iodoquinol 650 mg PO TID for 20 days
Related
trophozoite
General
Blastocystis
Properties
KINGDOM: animal
PHYLUM: protozoa
References
- Clinical Diagnosis & Management by Laboratory Methods,
19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia,
PA. 1996, pg 1274
- Medical Knowledge Self Assessment Program (MKSAP) 16,
American College of Physicians, Philadelphia 2012
- Tan KS, Mirza H, Teo JD, Wu B, Macary PA.
Current Views on the Clinical Relevance of Blastocystis spp.
Curr Infect Dis Rep. 2010 Jan;12(1):28-35
PMID: 21308496