Blastocystis hominis

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Blastocystis hominis
Four common forms of Blastocystis hominis Valzn.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Stramenopiles
Phylum: Bigyra
Class: Blastocystea
Order: Blastocystida
Family: Blastocystidae
Genus: Blastocystis
Species:
B. hominis
Binomial name
Blastocystis hominis

Blastocystis hominis is a single-celled eukaryotic organism that inhabits the gastrointestinal tract of humans and various animals. [1] This stramenopile exhibits significant genetic diversity and has become an organism of increasing scientific interest due to its widespread distribution and controversial role in human health. [2] Recent molecular studies have identified numerous subtypes, suggesting a complex evolutionary history and host-parasite relationship. [3] The organism is one of the most common intestinal protists in humans, with infection rates reaching up to 100% in some developing regions. [4] While commonly referred to as Blastocystis hominis in humans, the current taxonomic convention recognizes various species and subtypes within the genus Blastocystis , with at least 17 different subtypes identified through molecular analysis. [5]

Contents

Taxonomic history

Blastocystis hominis was initially misidentified as a yeast in the early 20th century and has undergone several taxonomic reclassifications. [6] Alexeieff (1911) initially classified it as a flagellate cyst, but Brumpt (1912) later established it as a distinct organism. [7] Modern molecular phylogenetic analyses have definitively assigned it to Stramenopiles, a diverse group of predominantly photosynthetic organisms. [8] Genetic studies have identified several subtypes, each with different host specificities and potential pathogenic abilities [9]

Blastocystis hominis External Transmission vs Auto-Infection Blastocystis hominis Morphology.png
Blastocystis hominis External Transmission vs Auto-Infection

Morphology

Blastocystis hominis demonstrates tremendous morphological plasticity throughout its life cycle. [11] The vacuolar form, which is most usually seen in laboratory cultures, has a large central vacuole surrounded by peripheral cytoplasm containing the nucleus and other organelles. [12] The granular form appears similar, but it has discrete granules within the central vacuole, which could represent metabolic products or reproductive elements. [13] The amoeboid type has an irregular shape with pseudopod-like extensions and is commonly seen in symptomatic patients. [14] Recent electron microscopy studies have shown sophisticated interior features, such as surface coat variations and organelles that resemble mitochondrion [15]

Life cycle

Various forms of Blastocystis sp in a life cycle. Blastocystis sp. Life cycle.png
Various forms of Blastocystis sp in a life cycle.

Blastocystis hominis has a multistage life cycle and is highly adaptable to a variety of host environments. [16] The illness develops when the cyst form is consumed by contaminated food or water. [17] When the cyst enters the colon, it grows into a vacuolar form, which is the key diagnostic stage usually seen in stool samples. [18]

The organism has two separate transmission patterns: external transmission and self-infection. During external transmission, thick-walled cysts discharged in feces can survive in the environment and stay infectious for long periods. [19] These environmentally resistant cysts enhance transmission between hosts via the fecal-oral pathway. [20]

In autoinfection, thin-walled cysts form from the vacuolar form and excyst within the intestine, sustaining infection in the same host. [6] The vacuolar shape can also transform into a multi-vacuolar. It may eventually transform into an amoeboid. The amoeboid stage, while less prevalent, is thought to play a role in pathogenicity. [21]

Binary fission is the principal mode of reproduction, occurring in both vacuolar and amoeboid forms. [22] Under stress conditions, such as unfavorable environmental factors or host immunological responses, the organism can generate pre-cyst stages that eventually develop into mature cysts. [23] This complicated life cycle, with its numerous physical forms, helps the organism colonize and spread to a wide range of host species. [24]

Clinical significance

Blastocystis isolated from stool sample of infected patient. Parasite140080-fig2 Gastrointestinal parasites in seven primates of the Tai National Park - Blastocystis.png
Blastocystis isolated from stool sample of infected patient.

There is still disagreement among scientists on Blastocystis hominis's capacity for pathogenicity. [24] Abdominal pain, recurrent diarrhea, and irritable bowel syndrome (IBS) are among the often reported clinical symptoms. [25] The existence of the organism in a large number of asymptomatic people, however, makes it more difficult to comprehend its potential for pathogenicity. [26] Current diagnostic techniques have progressed from basic microscopy to include molecular tools such as PCR-based techniques, [27] since studies have indicated possible links between Blastocystis infections [28] and changes in the gut microbiota. [29]

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References

  1. ↑ Stensvold, C. Rune; Clark, C. Graham (December 2016). "Current status of Blastocystis: A personal view" (PDF). Parasitology International. 65 (6): 763–771. doi:10.1016/j.parint.2016.05.015. ISSN   1383-5769. PMID   27247124.
  2. ↑ Andersen, Lee O'Brien; Stensvold, Christen Rune (March 2016). "Blastocystis in Health and Disease: Are We Moving from a Clinical to a Public Health Perspective?". Journal of Clinical Microbiology. 54 (3): 524–528. doi:10.1128/jcm.02520-15. ISSN   0095-1137. PMC   4767957 . PMID   26677249.
  3. ↑ Alfellani, Mohammed A.; Taner-Mulla, Derya; Jacob, Alison S.; Imeede, Christine Atim; Yoshikawa, Hisao; Stensvold, C. Rune; Clark, C. Graham (July 2013). "Genetic Diversity of Blastocystis in Livestock and Zoo Animals" (PDF). Protist. 164 (4): 497–509. doi:10.1016/j.protis.2013.05.003. ISSN   1434-4610. PMID   23770574.
  4. ↑ Deng, Lei; Chai, Yijun; Zhou, Ziyao; Liu, Haifeng; Zhong, Zhijun; Hu, Yanchun; Fu, Hualin; Yue, Chanjuan; Peng, Guangneng (2019). "Epidemiology of Blastocystis sp. infection in China: a systematic review". Parasite. 26: 41. doi:10.1051/parasite/2019042. ISSN   1776-1042. PMC   6632114 . PMID   31309925.
  5. ↑ Stensvold, Christen Rune; Clark, C. Graham (March 2020). "Pre-empting Pandora's Box: Blastocystis Subtypes Revisited" (PDF). Trends in Parasitology. 36 (3): 229–232. doi:10.1016/j.pt.2019.12.009. ISSN   1471-4922. PMID   32001133.
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  7. ↑ Anderson, T. R.; Slotkin, T. A. (1975-08-15). "Maturation of the adrenal medulla--IV. Effects of morphine". Biochemical Pharmacology. 24 (16): 1469–1474. doi:10.1016/0006-2952(75)90020-9. ISSN   1873-2968. PMID   7.
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  10. ↑ Mehlhorn, Heinz (2016). "Blastocystis hominis". In Mehlhorn, Heinz (ed.). Encyclopedia of Parasitology. Berlin, Heidelberg: Springer. pp. 1–3. doi:10.1007/978-3-642-27769-6_416-2. ISBN   978-3-642-27769-6.
  11. ↑ Schmoldt, A.; Benthe, H. F.; Haberland, G. (1975-09-01). "Digitoxin metabolism by rat liver microsomes". Biochemical Pharmacology. 24 (17): 1639–1641. ISSN   1873-2968. PMID   10.
  12. ↑ Lefkowitz, R. J. (1975-09-15). "Identification of adenylate cyclase-coupled beta-adrenergic receptors with radiolabeled beta-adrenergic antagonists". Biochemical Pharmacology. 24 (18): 1651–1658. doi:10.1016/0006-2952(75)90001-5. ISSN   0006-2952. PMID   11.
  13. ↑ Stein, J. M. (1975-09-15). "The effect of adrenaline and of alpha- and beta-adrenergic blocking agents on ATP concentration and on incorporation of 32Pi into ATP in rat fat cells". Biochemical Pharmacology. 24 (18): 1659–1662. doi:10.1016/0006-2952(75)90002-7. ISSN   0006-2952. PMID   12.
  14. ↑ Järvisalo, J.; Saris, N. E. (1975-09-15). "Action of propranolol on mitochondrial functions--effects on energized ion fluxes in the presence of valinomycin". Biochemical Pharmacology. 24 (18): 1701–1705. doi:10.1016/0006-2952(75)90009-x. ISSN   0006-2952. PMID   13.
  15. ↑ Bhagwat, V. M.; Ramachandran, B. V. (1975-09-15). "Malathion A and B esterases of mouse liver-I". Biochemical Pharmacology. 24 (18): 1713–1717. doi:10.1016/0006-2952(75)90011-8. ISSN   0006-2952. PMID   14.
  16. ↑ Tan, Kevin S. W. (October 2008). "New Insights on Classification, Identification, and Clinical Relevance of Blastocystis spp". Clinical Microbiology Reviews. 21 (4): 639–665. doi:10.1128/cmr.00022-08. ISSN   0893-8512. PMC   2570156 . PMID   18854485.
  17. ↑ Abe, Niichiro (March 2004). "Molecular and phylogenetic analysis of Blastocystis isolates from various hosts". Veterinary Parasitology. 120 (3): 235–242. doi:10.1016/j.vetpar.2004.01.003. ISSN   0304-4017. PMID   15041098.
  18. ↑ Sienzel, D.J.; Boreham, P.F.L.; McDougall, R. (November 1991). "Ultrastructure of Blastocystis hominis in human stool samples". International Journal for Parasitology. 21 (7): 807–812. doi:10.1016/0020-7519(91)90149-2. ISSN   0020-7519. PMID   1774117.
  19. ↑ Zhang, Xu; Qiao, JiYing; Wu, XiaoMin; Da, Rong; Zhao, LiMing; Wei, ZhiChao (January 2012). "In vitro culture of Blastocystis hominis in three liquid media and its usefulness in the diagnosis of blastocystosis". International Journal of Infectious Diseases. 16 (1): e23–e28. doi:10.1016/j.ijid.2011.09.012. ISSN   1201-9712. PMID   22047715.
  20. ↑ Jeremiah, SS; Parija, SubhashChandra (2013). "Blastocystis: Taxonomy, biology and virulence". Tropical Parasitology. 3 (1): 17–25. doi: 10.4103/2229-5070.113894 . ISSN   2229-5070. PMC   3745665 . PMID   23961437.
  21. ↑ Tan, T. C.; Suresh, K. G. (2005-12-02). "Predominance of amoeboid forms of Blastocystis hominis in isolates from symptomatic patients". Parasitology Research. 98 (3): 189–193. doi:10.1007/s00436-005-0033-7. ISSN   0932-0113. PMID   16323025.
  22. ↑ Zierdt, Charles H.; Williams, Reginald L. (October 1974). "Blastocystis hominis: Axenic cultivation". Experimental Parasitology. 36 (2): 233–243. doi:10.1016/0014-4894(74)90062-9. ISSN   0014-4894. PMID   4369819.
  23. ↑ Stenzel, D J; Boreham, P F (1996). "Blastocystis hominis revisited". Clinical Microbiology Reviews. 9 (4): 563–584. doi:10.1128/cmr.9.4.563-584.1996. ISSN   0893-8512. PMC   172910 . PMID   8894352.
  24. 1 2 Lepczyńska, M.; Białkowska, J.; Dzika, E.; Piskorz-Ogórek, K.; Korycińska, J. (2017-03-22). "Blastocystis: how do specific diets and human gut microbiota affect its development and pathogenicity?". European Journal of Clinical Microbiology & Infectious Diseases. 36 (9): 1531–1540. doi:10.1007/s10096-017-2965-0. ISSN   0934-9723. PMC   5554277 . PMID   28326446.
  25. ↑ Stensvold, Christen Rune; Andersen, Lee O'Brien; Gentekaki, Eleni (August 2024). "Towards minimizing second-generation mis-identification of Blastocystis". Trends in Parasitology. 40 (8): 670–674. doi:10.1016/j.pt.2024.06.001. ISSN   1471-4922. PMID   38871578.
  26. ↑ Knight, Richard (May 2010). "Blastocystis hominis infection". In Warrell, David A. (ed.). Oxford Textbook of Medicine (5 ed.). Oxford University Press. pp. 1118–1119. doi:10.1093/med/9780199204854.003.070809_update_001. ISBN   978-0-19-920485-4.
  27. ↑ Beghini, Francesco; Pasolli, Edoardo; Truong, Tin Duy; Putignani, Lorenza; Cacciò, Simone M; Segata, Nicola (2017-08-22). "Large-scale comparative metagenomics of Blastocystis, a common member of the human gut microbiome". The ISME Journal. 11 (12): 2848–2863. Bibcode:2017ISMEJ..11.2848B. doi:10.1038/ismej.2017.139. ISSN   1751-7362. PMC   5702742 . PMID   28837129.
  28. ↑ "Blastocystis hominis-Blastocystis hominis - Symptoms & causes". Mayo Clinic .
  29. ↑ Stensvold, C. Rune; Arendrup, Maiken C.; Jespersgaard, Cathrine; Mølbak, Kåre; Nielsen, Henrik V. (November 2007). "Detecting Blastocystis using parasitologic and DNA-based methods: a comparative study". Diagnostic Microbiology and Infectious Disease. 59 (3): 303–307. doi:10.1016/j.diagmicrobio.2007.06.003. ISSN   0732-8893. PMID   17913433.
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