Typhoid fever pathophysiology: Difference between revisions

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{{Typhoid fever}}
{{Typhoid fever}}


{{CMG}}
{{CMG}}; {{AE}}{{AA}}


== Overview ==
== Overview ==


== Pathophysiology ==
<br>
{{Family tree/start}}
{{Familytree|boxstyle=width: 300px; text-align: left; background: #FFF0F5| | | | A01 | | | |A01=  '''Innoculation'''
*Orofecal transmission
*Infective dose 1000 to 1 million
}}
{{Family tree | | | | |!| | | | | }}


{{Familytree|boxstyle=width: 300px; text-align: left;background: #FFF0F5| | | | B01 |-| B02| |B01='''Gastrointestinal Infection'''
==Pathogenesis==
The pathogenesis of typhoid fever consists of following sequence of events.
===Innoculation===
*Orofecal transmission.
*Infective dose 1000 to 1 million organisms.


'''''Stomach'''''
 
*Enters stomach
===Gastrointestinal Infection===
*High tolerance for acid
'''Stomach'''
*Survives PH as low as 1.5
*Bacterium enters stomach.
'''''Small intestine'''''
*Survives pH as low as 1.5
*Adherence to mucosal cells
'''Small intestine'''
*Invade mucosal M cells overlying payers patches
*Adherence to mucosal cells via special proteins.
*Internalisation in M cells
*Invade mucosal M cells overlying peyer's patches
*Translocation to underlying lymphoid tissue and draining lymph nodes
*Internalisation in M cells of ileum.
|B02= '''Systemic spread'''
*Translocation to underlying lymphoid tissue and draining lymph nodes.
*Dissemination of ''[[S.typhi]]'' to reticuloendothelial system
 
===Systemic spread===
*Dissemination of ''[[S.typhi]]'' to reticuloendothelial system.
*Spreads via lymph and blood
*Spreads via lymph and blood
*Replication within reticuloendothelial system
*Replication within reticuloendothelial system such as spleen, liver, bone marrow.
*Evades immune system  
*Evades immune system by hiding intracellularly within macrophages.
}}


}}
===Chronic carrier state===
{{Family tree | | | | |!| | | | | }}
{{Familytree|boxstyle=width: 300px; text-align: left;background: #FFF0F5 | | | |B01| | | |B01= '''Chronic carrier state'''
*Resides and multiplies in gall bladder
*Resides and multiplies in gall bladder
*Excretion in urine and stool}}
*Excretion in urine and stool infecting other individuals.
{{Family tree/end}}
 
== Genetics ==


Typhoid fever may be associtated with genes of the Class II and Class III Major Histocompatibility Complex.<ref>Dunstan, Sarah J., et al. "Genes of the class II and class III major histocompatibility complex are associated with typhoid fever in Vietnam." Journal of Infectious Diseases 183.2 (2001): 261-268.</ref>
Two types of HLA associations can be found with typhoid fever:<ref name="pmid12456854">{{cite journal| author=Parry CM, Hien TT, Dougan G, White NJ, Farrar JJ| title=Typhoid fever. | journal=N Engl J Med | year= 2002 | volume= 347 | issue= 22 | pages= 1770-82 | pmid=12456854 | doi=10.1056/NEJMra020201 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=12456854  }} </ref>
*HLA-DRB1*0301/6/8, HLA-DQB1*0201-3, and TNFA*2(–308) associated with increased susceptibility to typhoid fever.
*HLA-DRB1*04, HLA-DQB1*0401/2, and TNFA*1(–308)associated with increased disease resistance.


== References ==
== References ==
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{{WS}}
{{WS}}
[[Category:Infectious disease]]
[[Category:Gastroenterology]]

Revision as of 22:12, 30 August 2016


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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

Overview

Pathogenesis

The pathogenesis of typhoid fever consists of following sequence of events.

Innoculation

  • Orofecal transmission.
  • Infective dose 1000 to 1 million organisms.


Gastrointestinal Infection

Stomach

  • Bacterium enters stomach.
  • Survives pH as low as 1.5

Small intestine

  • Adherence to mucosal cells via special proteins.
  • Invade mucosal M cells overlying peyer's patches
  • Internalisation in M cells of ileum.
  • Translocation to underlying lymphoid tissue and draining lymph nodes.

Systemic spread

  • Dissemination of S.typhi to reticuloendothelial system.
  • Spreads via lymph and blood
  • Replication within reticuloendothelial system such as spleen, liver, bone marrow.
  • Evades immune system by hiding intracellularly within macrophages.

Chronic carrier state

  • Resides and multiplies in gall bladder
  • Excretion in urine and stool infecting other individuals.


References

Template:WH

Template:WS