Legionellosis pathophysiology: Difference between revisions
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{{Legionellosis}} | {{Legionellosis}} | ||
{{CMG}} | {{CMG}} [[Ogechukwu Hannah Nnabude, MD]] | ||
==Overview== | ==Overview== | ||
''[[Legionella]]'' is often transmitted by aerosolized droplets produced from contaminated whirlpool spa, river, cruise ships, cooling towers, air conditioners, water supply systems . ''L. pneumophila'' usually invades the host cells and replicates intracellularly. ''[[Legionella]]'' is internalized using [[pseudopods]] and protects itself in a membrane-bound vacuole that does not fuse with [[lysosomes]]. | |||
==Pathophysiology== | ==Pathophysiology== | ||
===Transmission=== | ===Transmission=== | ||
*''[[Legionella]]'' is acquired by inhaling droplets from contaminated water sources such as faucets, showers, humidifiers, whirlpool spa, river, cruise ships, cooling towers, air conditioners, water supply systems <ref name="pmid29104349">{{cite journal| author=Prussin AJ, Schwake DO, Marr LC| title=Ten Questions Concerning the Aerosolization and Transmission of Legionella in the Built Environment. | journal=Build Environ | year= 2017 | volume= 123 | issue= | pages= 684-695 | pmid=29104349 | doi=10.1016/j.buildenv.2017.06.024 | pmc=5665586 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=29104349 }} </ref>. ''L. longbeachae'' is thought to be transmitted by compost during gardening activity<ref name="pmid21943591">{{cite journal| author=Graham FF, White PS, Harte DJ, Kingham SP| title=Changing epidemiological trends of legionellosis in New Zealand, 1979-2009. | journal=Epidemiol Infect | year= 2012 | volume= 140 | issue= 8 | pages= 1481-96 | pmid=21943591 | doi=10.1017/S0950268811000975 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21943591 }} </ref>. However, it has also been seen in industrial coolers <ref name="pmid28625225">{{cite journal| author=Thornley CN, Harte DJ, Weir RP, Allen LJ, Knightbridge KJ, Wood PRT| title=Legionella longbeachae detected in an industrial cooling tower linked to a legionellosis outbreak, New Zealand, 2015; possible waterborne transmission? | journal=Epidemiol Infect | year= 2017 | volume= 145 | issue= 11 | pages= 2382-2389 | pmid=28625225 | doi=10.1017/S0950268817001170 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=28625225 }} </ref>. | |||
*Although is is believed that [[Legionella]] is not transmitted from one person to another person <ref name="pmid29250488">{{cite journal| author=Boamah DK, Zhou G, Ensminger AW, O'Connor TJ| title=From Many Hosts, One Accidental Pathogen: The Diverse Protozoan Hosts of Legionella. | journal=Front Cell Infect Microbiol | year= 2017 | volume= 7 | issue= | pages= 477 | pmid=29250488 | doi=10.3389/fcimb.2017.00477 | pmc=5714891 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=29250488 }} </ref>, there have been reports of person to person transmission <ref name="pmid26840151">{{cite journal| author=Correia AM, Ferreira JS, Borges V, Nunes A, Gomes B, Capucho R | display-authors=etal| title=Probable Person-to-Person Transmission of Legionnaires' Disease. | journal=N Engl J Med | year= 2016 | volume= 374 | issue= 5 | pages= 497-8 | pmid=26840151 | doi=10.1056/NEJMc1505356 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=26840151 }} </ref>. '' | |||
* Healthcare-associated transmission of ''[[Legionella]]'' is common and has a higher mortality rate. | |||
==Pathogenesis== | |||
*[[Legionella]] are able to live within amoebic cells. Free-living amoebae may be responsible for enabling [[Legionella]] to better survive environmental hazards, adapt to living within macrophages, and may be a significant reservoir of [[Legionella]]. These amoebae may assist [[Legionella]] to remain undetected within the human environments <ref name="pmid16524240">{{cite journal| author=Segovia Hernández M| title=[The journey of Legionella pneumophila from amoebae to macrophage. Reflections on the largest outbreak of legionnaire's disease]. | journal=An R Acad Nac Med (Madr) | year= 2005 | volume= 122 | issue= 3 | pages= 489-98; discussion 498-504 | pmid=16524240 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16524240 }} </ref>. | |||
*[[Legionella]] invades the host cells and replicates intracellularly. | |||
*The internalisation of the bacteria can be enhanced by the presence of [[antibody]] and [[Complement system|complement]] but is not absolutely required. | |||
*A [[pseudopod]] coils around the bacterium in this unique form of [[phagocytosis]]. | |||
*Once internalised, the bacteria surround themselves in a [[membrane]]-bound [[vacuole]] that does not fuse with [[lysosomes]] that would otherwise degrade the [[bacteria]]. In this protected compartment the bacteria multiply. | |||
*The bacteria use a Type IVB secretion system known as Icm/Dot to inject effector proteins into the host. | |||
*These effectors are involved in increasing the bacteria's ability to survive inside the host cell. They also secrete a 39kDa [[metalloprotease]] into culture fluids, which is [[cytotoxic]] for some cultured [[tissue]] culture cells. | |||
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==References== | ==References== | ||
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Ogechukwu Hannah Nnabude, MD
Overview
Legionella is often transmitted by aerosolized droplets produced from contaminated whirlpool spa, river, cruise ships, cooling towers, air conditioners, water supply systems . L. pneumophila usually invades the host cells and replicates intracellularly. Legionella is internalized using pseudopods and protects itself in a membrane-bound vacuole that does not fuse with lysosomes.
Pathophysiology
Transmission
- Legionella is acquired by inhaling droplets from contaminated water sources such as faucets, showers, humidifiers, whirlpool spa, river, cruise ships, cooling towers, air conditioners, water supply systems [1]. L. longbeachae is thought to be transmitted by compost during gardening activity[2]. However, it has also been seen in industrial coolers [3].
- Although is is believed that Legionella is not transmitted from one person to another person [4], there have been reports of person to person transmission [5].
- Healthcare-associated transmission of Legionella is common and has a higher mortality rate.
Pathogenesis
- Legionella are able to live within amoebic cells. Free-living amoebae may be responsible for enabling Legionella to better survive environmental hazards, adapt to living within macrophages, and may be a significant reservoir of Legionella. These amoebae may assist Legionella to remain undetected within the human environments [6].
- Legionella invades the host cells and replicates intracellularly.
- The internalisation of the bacteria can be enhanced by the presence of antibody and complement but is not absolutely required.
- A pseudopod coils around the bacterium in this unique form of phagocytosis.
- Once internalised, the bacteria surround themselves in a membrane-bound vacuole that does not fuse with lysosomes that would otherwise degrade the bacteria. In this protected compartment the bacteria multiply.
- The bacteria use a Type IVB secretion system known as Icm/Dot to inject effector proteins into the host.
- These effectors are involved in increasing the bacteria's ability to survive inside the host cell. They also secrete a 39kDa metalloprotease into culture fluids, which is cytotoxic for some cultured tissue culture cells.
References
- ↑ Prussin AJ, Schwake DO, Marr LC (2017). "Ten Questions Concerning the Aerosolization and Transmission of Legionella in the Built Environment". Build Environ. 123: 684–695. doi:10.1016/j.buildenv.2017.06.024. PMC 5665586. PMID 29104349.
- ↑ Graham FF, White PS, Harte DJ, Kingham SP (2012). "Changing epidemiological trends of legionellosis in New Zealand, 1979-2009". Epidemiol Infect. 140 (8): 1481–96. doi:10.1017/S0950268811000975. PMID 21943591.
- ↑ Thornley CN, Harte DJ, Weir RP, Allen LJ, Knightbridge KJ, Wood PRT (2017). "Legionella longbeachae detected in an industrial cooling tower linked to a legionellosis outbreak, New Zealand, 2015; possible waterborne transmission?". Epidemiol Infect. 145 (11): 2382–2389. doi:10.1017/S0950268817001170. PMID 28625225.
- ↑ Boamah DK, Zhou G, Ensminger AW, O'Connor TJ (2017). "From Many Hosts, One Accidental Pathogen: The Diverse Protozoan Hosts of Legionella". Front Cell Infect Microbiol. 7: 477. doi:10.3389/fcimb.2017.00477. PMC 5714891. PMID 29250488.
- ↑ Correia AM, Ferreira JS, Borges V, Nunes A, Gomes B, Capucho R; et al. (2016). "Probable Person-to-Person Transmission of Legionnaires' Disease". N Engl J Med. 374 (5): 497–8. doi:10.1056/NEJMc1505356. PMID 26840151.
- ↑ Segovia Hernández M (2005). "[The journey of Legionella pneumophila from amoebae to macrophage. Reflections on the largest outbreak of legionnaire's disease]". An R Acad Nac Med (Madr). 122 (3): 489–98, discussion 498-504. PMID 16524240.