Blastocystis hominis

Blastocystis hominis
Scientific classification Edit this classification
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]

Taxonomic history

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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]

Morphology

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Blastocystis hominis demonstrates tremendous morphological plasticity throughout its life cycle.[10] 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.[11] The granular form appears similar, but it has discrete granules within the central vacuole, which could represent metabolic products or reproductive elements.[12] The amoeboid type has an irregular shape with pseudopod-like extensions and is commonly seen in symptomatic patients.[13] Recent electron microscopy studies have shown sophisticated interior features, such as surface coat variations and organelles that resemble mitochondrion[14]

Life cycle

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Blastocystis hominis has a multistage life cycle and is highly adaptable to a variety of host environments.[15] The illness develops when the cyst form is consumed by contaminated food or water.[16] When the cyst enters the colon, it grows into a vacuolar form, which is the key diagnostic stage usually seen in stool samples.[17]

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.[18] These environmentally resistant cysts enhance transmission between hosts via the fecal-oral pathway.[19]

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.[20]

Binary fission is the principal mode of reproduction, occurring in both vacuolar and amoeboid forms.[21] 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.[22] This complicated life cycle, with its numerous physical forms, helps the organism colonize and spread to a wide range of host species.[23]

Clinical significance

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Blastocystis isolated from stool sample of infected patient.

There is still disagreement among scientists on Blastocystis hominis's capacity for pathogenicity.[23] Abdominal pain, recurrent diarrhea, and irritable bowel syndrome (IBS) are among the often reported clinical symptoms.[24] The existence of the organism in a large number of asymptomatic people, however, makes it more difficult to comprehend its potential for pathogenicity.[25] Current diagnostic techniques have progressed from basic microscopy to include molecular tools such as PCR-based techniques,[26] since studies have indicated possible links between Blastocystis infections[27] and changes in the gut microbiota.[28]

References

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  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.
  6. ^ a b Clark, C. Graham; van der Giezen, Mark; Alfellani, Mohammed A.; Stensvold, C. Rune (2013). "Chapter One - Recent Developments in Blastocystis Research". Advances in Parasitology. 82. Elsevier: 1–32. doi:10.1016/b978-0-12-407706-5.00001-0. ISBN 978-0-12-407706-5. PMID 23548084.
  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.
  8. ^ Moroi, K.; Sato, T. (1975-08-15). "Comparison between procaine and isocarboxazid metabolism in vitro by a liver microsomal amidase-esterase". Biochemical Pharmacology. 24 (16): 1517–1521. doi:10.1016/0006-2952(75)90029-5. ISSN 1873-2968. PMID 8.
  9. ^ Marniemi, J.; Parkki, M. G. (1975-09-01). "Radiochemical assay of glutathione S-epoxide transferase and its enhancement by phenobarbital in rat liver in vivo". Biochemical Pharmacology. 24 (17): 1569–1572. doi:10.1016/0006-2952(75)90080-5. ISSN 0006-2952. PMID 9.
  10. ^ 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.
  11. ^ 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.
  12. ^ 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.
  13. ^ 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.
  14. ^ 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.
  15. ^ 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.
  16. ^ 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.
  17. ^ 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.
  18. ^ 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.
  19. ^ 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.
  20. ^ 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.
  21. ^ 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.
  22. ^ 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.
  23. ^ a b 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.
  24. ^ 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.
  25. ^ 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.
  26. ^ 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.
  27. ^ "Blastocystis hominis-Blastocystis hominis - Symptoms & causes". Mayo Clinic.
  28. ^ 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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