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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==
''Legionella pneumophila'' and other Legionella species. At least 46 species and 70 serogroups have been identified. ''L.pneumophila'', an ubiquitous aquatic organism that thrives in warm environments (32°- 45°C) causes over 90% of LD in the United States. The disease has two distinct forms:
*Legionnaires' disease, the more severe form of infection which includes pneumonia, and
*Pontiac fever, a milder illness.
*Pontiac fever and Legionnaires’ disease may also be called “Legionellosis” (LEE-juh-nuh-low-sis) separately or together.
[[Image:Legionella pneumophila (SEM).jpg|thumb|200px|left|Colorized scanning [[electron micrograph]] (SEM) with moderately-high magnification of 8000X depicting a large grouping of [[Gram-negative]] Legionella pneumophila bacteria]]
[[Image:Lung tissue during legionellosis.jpg|thumb|200px|left|This micrograph depicted details seen in a lung tissue specimen from a Knoxville patient with fatal [[pneumonia]] due to Legionnaires’ disease. The tissue was stained using [[hematoxylin-eosin]] (H&E) stain. Legionella pneumophila are [[Gram-negative]] bacteria. Using H&E stain, these organisms, if present in the specimen, would stain a pink or red color. Note how the [[alveola]]r spaces are so congested with a [[leukocytic]] [[infiltrate]] in response to the infection.]]
===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.


People get Legionnaires' disease when they breathe in a mist or vapor (small droplets of water in the air) that has been contaminated with the bacteria. One example might be from breathing in the steam from a whirlpool spa that has not been properly cleaned and disinfected.
==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>.
The bacteria are NOT spread from one person to another person.  
*[[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.
Outbreaks are when two or more people become ill in the same place at about the same time, such as patients in hospitals. Hospital buildings have complex water systems, and many people in hospitals already have illnesses that increase their risk for Legionella infection.  
*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.
Other outbreaks have been linked to aerosol sources in the community, or with cruise ships and hotels, with the most likely sources being whirlpool spas, cooling towers (air-conditioning units from large buildings), and water used for drinking and bathing.
*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.
===Infections===
'''Intestinal Infections''': These may only occur as part of [[respiratory infection]]s, and where gastrointestinal symptoms have on occasion been described.
 
'''Extraintestinal Infections''': ''L. pneumophila'' is specifically considered as a [[pathogen]] of the [[respiratory tract]], where it is a cause of atypical pneumonia, also known as Legionnaires' disease. Other infections have also been reported, including [[haemodialysis fistulae]], [[pericarditis]] and wound and skin infections. [[Bacteraemia]] is often associated with Legionnaires' disease.
 
'''Infections of [[Protozoa]]''': Protozoa such as ''Harmanella vermiformis'' and related protozoa have been shown to be able to support the growth of ''L. pneumophila'' in tap water. Also ''[[Acanthamoeba]]'', ''Naegleria'' and ''[[Tetrahymena]]'' can be infected by ''L. pneumophila''. This pathway may be how these organisms survive in the environment.
==Sources==
* CDC Legionellosis [http://wwwnc.cdc.gov/travel/yellowbook/2012/chapter-3-infectious-diseases-related-to-travel/legionellosis-legionnaires-disease-and-pontiac-fever.htm][http://www.cdc.gov/legionella/patient_facts.htm]


==References==
==References==
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Latest revision as of 03:03, 20 April 2022

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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

  1. ↑ 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.
  2. ↑ 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.
  3. ↑ 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.
  4. ↑ 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.
  5. ↑ 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.
  6. ↑ 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.


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