Psittacosis pathophysiology: Difference between revisions
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{{Psittacosis}} | {{Psittacosis}} | ||
{{CMG}}; {{AE}} {{ADI}} | {{CMG}}; {{AE}} {{ADI}}, {{DAMI}} | ||
==Overview== | ==Overview== | ||
The major risk factor for acquiring psittacosis is exposure to birds. Transmission can occur either by inhalation of aerosolized organisms in form of dried feces or respiratory secretions or by direct contact with birds. | The major [[risk factor]] for acquiring [[psittacosis]] is exposure to [[birds]]. [[Transmission (medicine)|Transmission]] can occur either by inhalation of aerosolized organisms in form of dried [[feces]] or [[Respiratory system|respiratory]] secretions or by direct contact with [[birds]]. The exact [[molecular]] details of [[bacterial]] uptake are not well understood. It is speculated that [[chlamydial]] cell contact is a two-step process: reversible binding followed by irreversible attachment. The key to understanding the [[pathogenesis]] of [[C. psittaci|''C. psittaci'']] is that frequent and repeated episodes of reinfection are needed for the development of severe [[disease]]. Several studies also highlighted the critical importance of host [[microfilaments]], [[microtubules]], and [[Microtubule-associated protein|microtubule motor protein]]<nowiki/>s ([[kinesin]] and [[dynein]]) for uptake and [[intracellular]] development of [[C. psittaci|''C. psittaci'']] and other [[Chlamydia infection|''Chlamydia'' spp]]. As with other [[intracellular]] [[zoonoses]] such as [[Q fever]] and [[brucellosis]], the clinical conditions associated with [[psittacosis]] have been seen in many [[organ systems]] such as the [[pulmonary]], [[hepatic]], and [[CNS|central nervous systems]]. | ||
==Pathophysiology== | ==Pathophysiology== | ||
===Transmission=== | ===Transmission=== | ||
The exact molecular details of bacterial uptake are not well understood. Elementary bodies (EBs) of [[C. psittaci]] are thought to infect their target cells in the lung by attachment to the base of cell surface [[microvilli]], where they are actively engulfed by [[endocytosis]] or [[phagocytosis]]. Further studies on the [[C. psittaci]]-related species of C. caviae showed that initial attachment is mediated by electrostatic interactions, most likely with [[glycosaminoglycan]] (GAG) moieties on the host cell surface. However, the observation that cellular binding of [[C. psittaci]] and related [[chlamydial]] strains is only partially or not inhibited by [[heparin]] strongly suggests that further adherence mechanisms contribute to [[chlamydial]] attachment. It was speculated that [[chlamydial]] cell contact is a two-step process | The exact [[molecular]] details of [[bacterial]] uptake are not well understood. Elementary bodies (EBs) of [[C. psittaci|''C. psittaci'']] are thought to [[infect]] their target cells in the [[lung]] by attachment to the base of cell surface [[microvilli]], where they are actively engulfed by [[endocytosis]] or [[phagocytosis]]. Further studies on the [[C. psittaci|''C. psittaci'']]-related species of ''C. caviae'' showed that initial attachment is mediated by electrostatic interactions, most likely with [[glycosaminoglycan]] ([[Glycosaminoglycan|GAG]]) moieties on the host cell surface. However, the observation that cellular binding of [[C. psittaci|''C. psittaci'']] and related [[chlamydial]] strains is only partially or not inhibited by [[heparin]] strongly suggests that further adherence mechanisms contribute to [[chlamydial]] attachment. It was speculated that [[chlamydial]] cell contact is a two-step process: | ||
# Reversible binding | |||
# Irreversible attachment | |||
Although [[chlamydial]] entry is extremely efficient, the exact [[molecular]] details of [[bacterial]] uptake are not well understood. The host [[protein disulfide isomerase]] ([[PDI]]) has been identified as being essential for both [[C. psittaci|''C. psittaci'']] attachment and entry into cells. [[PDI]] is highly enriched in the [[endoplasmic reticulum]], but is also found on the cell surface where it catalyzes [[reduction]], [[oxidation]], and [[isomerization]] of [[Disulfide bond|disulfide bonds]]. | |||
==Pathogenesis== | |||
The key to understanding the [[pathogenesis]] of [[C. psittaci|''C. psittaci'']] is that frequent and repeated episodes of reinfection are needed for the development of severe [[disease]].<ref name="pmid3571982">{{cite journal| author=Taylor HR, Johnson SL, Schachter J, Caldwell HD, Prendergast RA| title=Pathogenesis of trachoma: the stimulus for inflammation. | journal=J Immunol | year= 1987 | volume= 138 | issue= 9 | pages= 3023-7 | pmid=3571982 | doi= | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=3571982 }} </ref> Repeated episodes of [[infection]] induce a marked and sustained inflammatory response that, with time, leads to scarring and structural damage. A one time exposure to birds is not enough to develop [[psittacosis]]; consequently, those at greatest risk are individuals with leisure or occupational exposure to birds, including pet bird owners, [[Veterinarian|veterinarians]], pet shop employees, and poultry-processing plant employees. As a result, cases of [[psittacosis]] can range from a sporadic case in a pet bird owner to an [[outbreak]] affecting several hundred birds in a commercial flock and multiple infected workers.<ref name="pmid18387139">{{cite journal| author=Gaede W, Reckling KF, Dresenkamp B, Kenklies S, Schubert E, Noack U et al.| title=Chlamydophila psittaci infections in humans during an outbreak of psittacosis from poultry in Germany. | journal=Zoonoses Public Health | year= 2008 | volume= 55 | issue= 4 | pages= 184-8 | pmid=18387139 | doi=10.1111/j.1863-2378.2008.01108.x | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18387139 }} </ref> | |||
== | ==Microscopic Pathology== | ||
Several studies also highlighted the critical importance of host [[Microfilament|microfilaments]], [[microtubules]] and microtubule motor proteins ([[kinesin]] and [[dynein]]) for uptake and intracellular development of [[C. psittaci]] and other [[Chlamydia|Chlamydia spp]]. In all cell types tested, participation of [[actin]] and [[tubulin]] seems to be necessary for optimal bacterial proliferation. It was also noted that the shutdown of [[prokaryotic]] protein synthesis seemed to have no effect on [[C. psittaci]] uptake, thus demonstrating that the internalization process does not require protein synthesis on the bacterial side. Once internalized in the early inclusion, the infecting EB transforms into a larger and more conventional bacterial form, the reticulate body (RB). Subsequently, the RB-containing inclusions translocate through a [[cytoskeleton]]-dependent mechanism to the [[Perinuclear space|perinuclear region]], and RBs replicate by [[binary fission]]. The mechanisms by which [[C. psittaci]] manages its intracellular survival are still under intensive investigation. | Several studies also highlighted the critical importance of host [[Microfilament|microfilaments]], [[microtubules]], and [[Microtubule-associated protein|microtubule motor proteins]] ([[kinesin]] and [[dynein]]) for uptake and [[intracellular]] development of [[C. psittaci|''C. psittaci'']] and other [[Chlamydia|''Chlamydia'' spp]]. In all cell types tested, participation of [[actin]] and [[tubulin]] seems to be necessary for optimal [[bacterial]] proliferation. It was also noted that the shutdown of [[prokaryotic]] protein synthesis seemed to have no effect on [[C. psittaci|''C. psittaci'']] uptake, thus demonstrating that the internalization process does not require protein synthesis on the bacterial side. Once internalized in the early inclusion, the infecting EB transforms into a larger and more conventional [[bacterial]] form, the [[Reticular formation|reticulate body]] (RB). Subsequently, the RB-containing inclusions translocate through a [[cytoskeleton]]-dependent mechanism to the [[Perinuclear space|perinuclear region]], and RBs replicate by [[binary fission]]. The mechanisms by which [[C. psittaci|''C. psittaci'']] manages its intracellular survival are still under intensive investigation. | ||
== Associated conditions == | |||
As with other intracellular [[zoonoses]] such as [[Q fever]] and [[brucella|brucellosis]], the clinical conditions associated with psittacosis have been seen in the following [[organ systems]]: | |||
As with other intracellular zoonoses such as [[ | |||
*[[Pulmonary]] | *[[Pulmonary]] | ||
*[[Hepatic]] | *[[Hepatic]] | ||
| Line 30: | Line 29: | ||
*[[Renal]] | *[[Renal]] | ||
*[[Rheumatic]] | *[[Rheumatic]] | ||
*[[Hematologic]] and [[respiratory]] symptoms are frequently mild or absent on presentation | *[[Hematologic]] and [[respiratory]] symptoms are frequently mild or absent on presentation | ||
Disease severity can range from subclinical infection to [[fulminant]] sepsis with [[Multiorgan failure|multiorgan]] failure in previously healthy individuals, which may occasionally be fatal despite appropriate treatment. | [[Disease]] severity can range from subclinical [[infection]] to [[fulminant]] [[sepsis]] with [[Multiorgan failure|multiorgan]] failure in previously healthy individuals, which may occasionally be fatal despite appropriate treatment. | ||
==References== | ==References== | ||
{{reflist|2}} | {{reflist|2}} | ||
[[Category:Emergency mdicine]] | |||
[[Category:Disease]] | |||
[[Category:Up-To-Date]] | |||
[[Category:Infectious disease]] | |||
[[Category:Pulmonology]] | [[Category:Pulmonology]] | ||
Latest revision as of 23:51, 29 July 2020
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2], Omodamola Aje B.Sc, M.D. [3]
Overview
The major risk factor for acquiring psittacosis is exposure to birds. Transmission can occur either by inhalation of aerosolized organisms in form of dried feces or respiratory secretions or by direct contact with birds. The exact molecular details of bacterial uptake are not well understood. It is speculated that chlamydial cell contact is a two-step process: reversible binding followed by irreversible attachment. The key to understanding the pathogenesis of C. psittaci is that frequent and repeated episodes of reinfection are needed for the development of severe disease. Several studies also highlighted the critical importance of host microfilaments, microtubules, and microtubule motor proteins (kinesin and dynein) for uptake and intracellular development of C. psittaci and other Chlamydia spp. As with other intracellular zoonoses such as Q fever and brucellosis, the clinical conditions associated with psittacosis have been seen in many organ systems such as the pulmonary, hepatic, and central nervous systems.
Pathophysiology
Transmission
The exact molecular details of bacterial uptake are not well understood. Elementary bodies (EBs) of C. psittaci are thought to infect their target cells in the lung by attachment to the base of cell surface microvilli, where they are actively engulfed by endocytosis or phagocytosis. Further studies on the C. psittaci-related species of C. caviae showed that initial attachment is mediated by electrostatic interactions, most likely with glycosaminoglycan (GAG) moieties on the host cell surface. However, the observation that cellular binding of C. psittaci and related chlamydial strains is only partially or not inhibited by heparin strongly suggests that further adherence mechanisms contribute to chlamydial attachment. It was speculated that chlamydial cell contact is a two-step process:
- Reversible binding
- Irreversible attachment
Although chlamydial entry is extremely efficient, the exact molecular details of bacterial uptake are not well understood. The host protein disulfide isomerase (PDI) has been identified as being essential for both C. psittaci attachment and entry into cells. PDI is highly enriched in the endoplasmic reticulum, but is also found on the cell surface where it catalyzes reduction, oxidation, and isomerization of disulfide bonds.
Pathogenesis
The key to understanding the pathogenesis of C. psittaci is that frequent and repeated episodes of reinfection are needed for the development of severe disease.[1] Repeated episodes of infection induce a marked and sustained inflammatory response that, with time, leads to scarring and structural damage. A one time exposure to birds is not enough to develop psittacosis; consequently, those at greatest risk are individuals with leisure or occupational exposure to birds, including pet bird owners, veterinarians, pet shop employees, and poultry-processing plant employees. As a result, cases of psittacosis can range from a sporadic case in a pet bird owner to an outbreak affecting several hundred birds in a commercial flock and multiple infected workers.[2]
Microscopic Pathology
Several studies also highlighted the critical importance of host microfilaments, microtubules, and microtubule motor proteins (kinesin and dynein) for uptake and intracellular development of C. psittaci and other Chlamydia spp. In all cell types tested, participation of actin and tubulin seems to be necessary for optimal bacterial proliferation. It was also noted that the shutdown of prokaryotic protein synthesis seemed to have no effect on C. psittaci uptake, thus demonstrating that the internalization process does not require protein synthesis on the bacterial side. Once internalized in the early inclusion, the infecting EB transforms into a larger and more conventional bacterial form, the reticulate body (RB). Subsequently, the RB-containing inclusions translocate through a cytoskeleton-dependent mechanism to the perinuclear region, and RBs replicate by binary fission. The mechanisms by which C. psittaci manages its intracellular survival are still under intensive investigation.
Associated conditions
As with other intracellular zoonoses such as Q fever and brucellosis, the clinical conditions associated with psittacosis have been seen in the following organ systems:
- Pulmonary
- Hepatic
- Central nervous system
- Cardiac
- Renal
- Rheumatic
- Hematologic and respiratory symptoms are frequently mild or absent on presentation
Disease severity can range from subclinical infection to fulminant sepsis with multiorgan failure in previously healthy individuals, which may occasionally be fatal despite appropriate treatment.
References
- ↑ Taylor HR, Johnson SL, Schachter J, Caldwell HD, Prendergast RA (1987). "Pathogenesis of trachoma: the stimulus for inflammation". J Immunol. 138 (9): 3023–7. PMID 3571982.
- ↑ Gaede W, Reckling KF, Dresenkamp B, Kenklies S, Schubert E, Noack U; et al. (2008). "Chlamydophila psittaci infections in humans during an outbreak of psittacosis from poultry in Germany". Zoonoses Public Health. 55 (4): 184–8. doi:10.1111/j.1863-2378.2008.01108.x. PMID 18387139.