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Clin Microbiol Rev. Jan 1991; 4(1): 61–79.
PMCID: PMC358179

Blastocystis hominis--past and future.

Abstract

The history of B. hominis is unique. Few infectious agents have provoked the many misconceptions that plague this enigmatic parasitic ameba. Conflicting descriptions of its nature and pathogenesis have continued throughout the 20th century. As seen by the greatly expanded number of reports in recent years, B. hominis is now a major subject of study, particularly for evidence of disease causation. Physicians are treating patients with intestinal disease caused by B. hominis. Many mild cases resolve in about 3 days without treatment, but others are acute and chronic disease is common. As with E. histolytica, the carrier state is often seen without symptoms. Treatment is usually with metronidazole, but emetine (for refractory infections), trimethoprim-sulfamethoxazole, and pentamidine are also effective. In fecal samples, this complex protozoan appears in a variety of cell forms which makes microscopic diagnosis difficult. As yet, no specific fluorescent-antibody test is available for diagnosis. A culture method to demonstrate the more easily recognized CB form is available, but probably not feasible for most diagnostic laboratories. The common cell forms are the CB form, the granular (mitochondria) form, and the ameba form. The unexpected size range of these forms in clinical material, from yeast size (ca. 7 microns) to giant cells of 20 to 40 microns, makes diagnosis difficult Pseudopodia may be demonstrated by the ameba form in heated microscope stage culture chambers. The anaerobic B. hominis has no cyst form. Its mitochondria are uniquely anaerobic and have no cytochrome protein or oxidative mitochondrial enzymes. Because of its many cell forms and anaerobic mitochondria, B. hominis is an organism of great interest for morphologic and biochemical study. Reproduction is asexual, usually by binary fission. Shizogony occurs in cultured cells. The CB appears to be an organelle whose specific purpose is for reproduction by shizogony. From 2 to 30 progeny are derived from schizogony. The ameba form reproduces by plasmotomy; it has no CB. The pathology of B. hominis infections has been studied in gnotobiotic guinea pigs in which inflammation of the intestinal mucosa and invasion of the superficial layers were seen. Only limited studies of human pathology are available. Those who have studied mucosal histopathology report inflammation and cellular changes that resolve after treatment. More study in this area is strongly indicated (32, 44, 57, 62, 67, 75). Ultrastructural details of B. hominis major forms, except for the schizont, are complete. The organism has no cell wall. The concentric CB takes up as much as 95% of the cell. The major organelles, which include multiple nuclei, Golgi apparatus, mitochondria, endoplasmic reticulum, fat, and other inclusions, are confined in two or four opposed pods in a thin band of peripheral cytoplasm between the spherical entire plasma membrane and the CB membrane. The pods buldge the CB membrane inward. There is evidence of a bacteroid endosymbiont. Education about B. hominis is needed. Entry of recent findings into new textbooks is imperative for its understanding among medical practitioners. Laboratory workers need to be aware of it for many reasons. The College of American Pathologists includes B. hominis in its proficiency testing samples and requires that it be reported from clinical samples.

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Selected References

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  • Babcock D, Houston R, Kumaki D, Shlim D. Blastocystis hominis in Kathmandu, Nepal. N Engl J Med. 1985 Nov 28;313(22):1419–1419. [PubMed]
  • Chen JL, Vaudry WL, Kowalewska K, Wenman WM. Lack of serum immune response to Blastocystis hominis. Lancet. 1987 Oct 31;2(8566):1021–1021. [PubMed]
  • Cross JH. Recent advances in human protozoan parasites of the gastrointestinal tract. Int J Parasitol. 1987 Feb;17(1):151–158. [PubMed]
  • Diaczok BJ, Rival J. Diarrhea due to Blastocystis hominis: an old organism revisited. South Med J. 1987 Jul;80(7):931–932. [PubMed]
  • Diamond LS. Techniques of axenic cultivation of Entamoeba histolytica Schaudinn, 1903 and E. histolytica-like amebae. J Parasitol. 1968 Oct;54(5):1047–1056. [PubMed]
  • Doyle PW, Helgason MM, Mathias RG, Proctor EM. Epidemiology and pathogenicity of Blastocystis hominis. J Clin Microbiol. 1990 Jan;28(1):116–121. [PMC free article] [PubMed]
  • Dunn LA, Boreham PF, Stenzel DJ. Ultrastructural variation of Blastocystis hominis stocks in culture. Int J Parasitol. 1989 Feb;19(1):43–56. [PubMed]
  • Gallagher PG, Venglarcik JS., 3rd Blastocystis hominis enteritis. Pediatr Infect Dis. 1985 Sep-Oct;4(5):556–557. [PubMed]
  • Clinical relevance of Blastocystis hominis. Lancet. 1984 Jun 2;1(8388):1233–1234. [PubMed]
  • Guglielmetti P, Cellesi C, Figura N, Rossolini A. Family outbreak of Blastocystis hominis associated gastroenteritis. Lancet. 1989 Dec 9;2(8676):1394–1394. [PubMed]
  • Guirges SY, Al-Waili NS. Blastocystis hominis: evidence for human pathogenicity and effectiveness of metronidazole therapy. Clin Exp Pharmacol Physiol. 1987 Apr;14(4):333–335. [PubMed]
  • Johnson AM, Thanou A, Boreham PF, Baverstock PR. Blastocystis hominis: phylogenetic affinities determined by rRNA sequence comparison. Exp Parasitol. 1989 Apr;68(3):283–288. [PubMed]
  • LeBar WD, Larsen EC, Patel K. Afebrile diarrhea and Blastocystis hominis. Ann Intern Med. 1985 Aug;103(2):306–306. [PubMed]
  • Levine ND, Corliss JO, Cox FE, Deroux G, Grain J, Honigberg BM, Leedale GF, Loeblich AR, 3rd, Lom J, Lynn D, et al. A newly revised classification of the protozoa. J Protozool. 1980 Feb;27(1):37–58. [PubMed]
  • Llibre JM, Tor J, Manterola JM, Carbonell C, Foz M. Blastocystis hominis chronic diarrhoea in AIDS patients. Lancet. 1989 Jan 28;1(8631):221–221. [PubMed]
  • Lynch KM. Blastocystis hominis: Its Characteristics and its Prevalance in Intestinal Content and Feces in South Carolina. J Bacteriol. 1917 Jul;2(4):369–377. [PMC free article] [PubMed]
  • Markell EK, Udkow MP. Blastocystis hominis: pathogen or fellow traveler? Am J Trop Med Hyg. 1986 Sep;35(5):1023–1026. [PubMed]
  • McClure HM, Strobert EA, Healy GR. Blastocystis hominis in a pig-tailed macaque: a potential enteric pathogen for nonhuman primates. Lab Anim Sci. 1980 Oct;30(5):890–894. [PubMed]
  • Miller RA, Minshew BH. Blastocystis hominis: an organism in search of a disease. Rev Infect Dis. 1988 Sep-Oct;10(5):930–938. [PubMed]
  • Narkewicz MR, Janoff EN, Sokol RJ, Levin MJ. Blastocystis hominis gastroenteritis in a hemophiliac with acquired immune deficiency syndrome. J Pediatr Gastroenterol Nutr. 1989 Jan;8(1):125–128. [PubMed]
  • Nguyen XM, Krech T. Blastocystis hominis, ein parasitärer Durchfallerreger. Schweiz Med Wochenschr. 1989 Apr 15;119(15):457–460. [PubMed]
  • Phillips BP, Zierdt CH. Blastocystis hominis: pathogenic potential in human patients and in gnotobiotes. Exp Parasitol. 1976 Jun;39(3):358–364. [PubMed]
  • Qadri SM, al-Okaili GA, al-Dayel F. Clinical significance of Blastocystis hominis. J Clin Microbiol. 1989 Nov;27(11):2407–2409. [PMC free article] [PubMed]
  • Reinthaler FF, Mascher F, Klem G, Sixl W. A survey of gastrointestinal parasites in Ogun State, southwest Nigeria. Ann Trop Med Parasitol. 1988 Apr;82(2):181–184. [PubMed]
  • Ricci N, Toma P, Furlani M, Caselli M, Gullini S. Blastocystis hominis: a neglected cause of diarrhoea? Lancet. 1984 Apr 28;1(8383):966–966. [PubMed]
  • Russo AR, Stone SL, Taplin ME, Snapper HJ, Doern GV. Presumptive evidence for Blastocystis hominis as a cause of colitis. Arch Intern Med. 1988 May;148(5):1064–1064. [PubMed]
  • Sheehan DJ, Raucher BG, McKitrick JC. Association of Blastocystis hominis with signs and symptoms of human disease. J Clin Microbiol. 1986 Oct;24(4):548–550. [PMC free article] [PubMed]
  • Tan HK, Harrison M, Zierdt CH. Freeze-etch studies of the granular and vacuolated forms of Blastocystis horminis. Z Parasitenkd. 1974;44(4):267–278. [PubMed]
  • Tan HK, Zierdt CH. Ultrastructure of Blastocystis hominis. Z Parasitenkd. 1973 Nov 23;42(4):315–324. [PubMed]
  • Taylor DN, Houston R, Shlim DR, Bhaibulaya M, Ungar BL, Echeverria P. Etiology of diarrhea among travelers and foreign residents in Nepal. JAMA. 1988 Sep 2;260(9):1245–1248. [PubMed]
  • Tsang TK, Levin BS, Morse SR. Terminal ileitis associated with Blastocystis hominis infection. Am J Gastroenterol. 1989 Jul;84(7):798–799. [PubMed]
  • Vannatta JB, Adamson D, Mullican K. Blastocystis hominis infection presenting as recurrent diarrhea. Ann Intern Med. 1985 Apr;102(4):495–496. [PubMed]
  • Wilson KW, Winget D, Wilks S. Blastocystis hominis infection: signs and symptoms in patients at Wilford Hall Medical Center. Mil Med. 1990 Sep;155(9):394–396. [PubMed]
  • Wolfe MS. The treatment of intestinal protozoan infections. Med Clin North Am. 1982 May;66(3):707–720. [PubMed]
  • Wolyńska M, Soroczan W. Blastocystis hominis Brumpt, 1912 (Phycomycetes) w narzadzie rodnym kobiety. Pol Tyg Lek. 1972 May 22;27(21):788–791. [PubMed]
  • Zierdt CH. Studies of Blastocystis hominis. J Protozool. 1973 Feb;20(1):114–121. [PubMed]
  • Zierdt CH, Swan JC, Hosseini J. In vitro response of Blastocystis hominis to antiprotozoal drugs. J Protozool. 1983 May;30(2):332–334. [PubMed]
  • Zierdt CH. Cytochrome-free mitochondria of an anaerobic protozoan--Blastocystis hominis. J Protozool. 1986 Feb;33(1):67–69. [PubMed]
  • Zierdt CH. Blastocystis hominis, a long-misunderstood intestinal parasite. Parasitol Today. 1988 Jan;4(1):15–17. [PubMed]
  • Zierdt CH, Donnolley CT, Muller J, Constantopoulos G. Biochemical and ultrastructural study of Blastocystis hominis. J Clin Microbiol. 1988 May;26(5):965–970. [PMC free article] [PubMed]
  • Zierdt CH, Rude WS, Bull BS. Protozoan characteristics of Blastocystis hominis. Am J Clin Pathol. 1967 Nov;48(5):495–501. [PubMed]
  • Zierdt CH, Swan JC. Generation time and growth rate of the human intestinal parasite Blastocystis hominis. J Protozool. 1981 Nov;28(4):483–485. [PubMed]
  • Zierdt CH, Tan H. Endosymbiosis in Blastocystis hominis. Exp Parasitol. 1976 Jun;39(3):422–430. [PubMed]
  • Zierdt CH, Tan HK. Ultrastructure and light microscope appearance of Blastocystis hominis in a patient with enteric disease. Z Parasitenkd. 1976 Oct 12;50(3):277–283. [PubMed]
  • Zierdt CH, Williams RL. Blastocystis hominis: axenic cultivation. Exp Parasitol. 1974 Oct;36(2):233–243. [PubMed]

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