Intracellular parasite
Intracellular parasites are parasitic microorganisms - microparasites that are capable of growing and reproducing inside the cells of a host.
Facultative
Facultative intracellular parasites are capable of living and reproducing either inside or outside cells.
Bacterial examples include
- Francisella tularensis
- Listeria monocytogenes
- Salmonella[1]
- Brucella
- Legionella
- Mycobacterium
- Nocardia
- Rhodococcus equi[2]
- Yersinia
- Neisseria meningitidis[3]
Fungal examples include:
Obligate
Obligate intracellular parasites cannot reproduce outside their host cell, meaning that the parasite's reproduction is entirely reliant on intracellular resources.
Obligate intracellular parasites of humans include:
- Certain species of Mycobacterium such as Mycobacterium leprae
- Certain protozoa, including:
- Apicomplexans (Plasmodium spp., Toxoplasma gondii and Cryptosporidium parvum[7])
- Trypanosomatids (Leishmania spp. and Trypanosoma cruzi)
- Certain fungi
The mitochondria in eukaryotic cells may also have originally been such parasites, but ended up forming a mutualistic relationship (endosymbiotic theory).[citation needed]
Study of obligate pathogens is difficult because they cannot usually be reproduced outside the host. However, in 2009 scientists reported a technique allowing the Q-fever pathogen Coxiella burnetii to grow in an axenic culture and suggested the technique may be useful for study of other pathogens.[9]
Nutrition
The majority of Intracellular parasites must keep host cells alive as long as possible while they are reproducing and growing. In order to grow they need nutrients that might be scarce in their free form in the cell. To study the mechanism that intracellular parasites use to obtain nutrients Legionella pneumophila, a facultative intracellular parasite, has been used as a model. Thus we know that Legionella pneumophila obtains nutrients by promoting host proteasomal degradation. Self-degradation of host proteins into amino acids provides the parasite the primary carbon and energy source.[10]
Susceptibility
People with T cell deficiencies are particularly susceptible to intracellular pathogens.[11]
References
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instead. - ^ Spinosa MR, Progida C, Talà A, Cogli L, Alifano P, Bucci C (2007). "The Neisseria meningitidis capsule is important for intracellular survival in human cells". Infect. Immun. 75 (7): 3594–603. doi:10.1128/IAI.01945-06. PMC 1932921. PMID 17470547.
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ignored (help)CS1 maint: multiple names: authors list (link) - ^ Sebghati TS, Engle JT, Goldman WE (2000). "Intracellular parasitism by Histoplasma capsulatum: fungal virulence and calcium dependence". Science. 290 (5495): 1368–72. doi:10.1126/science.290.5495.1368. PMID 11082066.
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instead. - ^ Amann R, Springer N, Schönhuber W; et al. (1997). "Obligate intracellular bacterial parasites of acanthamoebae related to Chlamydia spp". Applied and environmental microbiology. 63 (1): 115–21. PMC 168308. PMID 8979345.
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instead. - ^ Page 28 in: Title: Rook's textbook of dermatology, Volume 4, Rook's Textbook of Dermatology, Tony Burns (FRCP.) Authors: Arthur Rook, Tony Burns (FRCP.) Edition: 8 Publisher: John Wiley and Sons, 2010 ISBN 1-4051-6169-8, ISBN 978-1-4051-6169-5
- ^ Omsland, Anders; Cockrell, Diane C.; Howe, Dale; Fischer, Elizabeth R.; Virtaneva, Kimmo; Sturdevant, Daniel E.; Porcella, Stephen F.; Heinzen, Robert A. (2009 Mar 17). "Host cell-free growth of the Q fever bacterium Coxiella burnetii". Proceedings of the National Academy of Science USA. 106 (11): 4430–4. doi:10.1073/pnas.0812074106. PMC 2657411. PMID 19246385.
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(help) - ^ Heuner K; Swanson M (editors). (2008). Legionella: Molecular Microbiology. Caister Academic Press.
- ^ Page 432, Chapter 22, in: Jones, Jane; Bannister, Barbara A.; Gillespie, Stephen H. (2006). Infection: Microbiology and Management. Wiley-Blackwell. ISBN 1-4051-2665-5.
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