Difference between revisions of "Yersinia"

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#REDIRECT[[:Category:Yersinia species]]
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===Overview===
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*Cause [[Intestine Pathogens - Pathology|intestinal disease]] in animals and are important zoonoses
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*10 species of which [[Yersinia pestis|''Y. pestis'']], [[Yersinia pseudotuberculosis|''Y. pseudotuberculosis]] and [[Yersinia enterocolitica|''Y. enterocolitica'']] are pathogenic to animals and humans; [[Yersinia pestis|''Y. pestis'']] is the most pathogenic
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*Rodents provide a reservoir of [[Yersinia pestis|''Y. pestis'']], which is the cause of human plague; fleas transmit the infection to other animals and humans
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*[[Yersinia pseudotuberculosis|''Y. pseudotuberculosis'']] and [[Yersinia enterocolitica|''Y. enterocolitica'']] reside in the intestine of domestic and wild animals and birds
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*Birds may cause mechanical transfer of the organisms
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===Characteristics===
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*Enterobacteria, but grow more slowly and at lower temperatures than other enterobacteria
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*Gram negative, non-spore forming, facultative anaerobes - rods or colibacilli
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*Non-lactose fermentors
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*Facultative intracellular pathogens
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*Show bipolar staining in Giemsa-stained smears from animal tissue
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*Pathogenic strains identified by serotyping and biotyping
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===Pathogenesis===
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*''Y. enterocolitica and [[Yersinia pseudotuberculosis|''Y. pseudotuberculosis'']] enter the intestinal mucosa via M cells of the Peyer's patches
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*Engulfed by macrphages in the mucosa
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*All three invasive species are facultative intracellular organisms and grow inside macrophages
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*Plasmid and chromosomal-encoded virulence factors required for survival and multiplication in macrophages
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*Survive in phagolysosomes and do not interfere with degranulation or lysosomal fusion
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*Resistant to macrophage killing mechanisms
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*Antiphagocytic proteins secreted by the organisms interfere with host [[Neutrophils - WikiBlood|neutrophils]]
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*[[Yersinia pestis|''Y. pestis'']] is more invasive than the other species and also possesses and antiphagocytic capsule and a plasminogen activator which aids systemic spread; endotoxin also contributes to its pathogenicity
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*Transport within macrophages to mesenteric lymph nodes
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*Replication in lymph nodes and development of necrotic lesions, with neutrophil invasion
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*The bacteria destroy the macrophages causing septicaemia
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 +
 
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===Clinical infections===
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*''[[Yersinia pestis]]''
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*''[[Yersinia pseudotuberculosis]]''
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**Less virulent than ''Y. pestis'' but closely related
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**Mainly infect animals
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**One plasmid, required for virulence
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**Sporadic cases of pseudotuberculosis in animals and man
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**Wild birds and rodents provide a reservoir of infection by harbouring the the pathogen in their intestinal tract
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**Sources include food and water contaminated by faeces
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**Pseudotuberculosis (caseous abscesses) in rodents, guinea pigs, cats, turkeys
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**Epidymo-orchitis in rams
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**Abortion in goats
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**Occasional infections in pigs, cattle, sheep
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**Multiplication in macrophages leads to granuloma formation
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**Granulomas occur in the gut wall and mesenteric lymph nodes
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**Occasional spread from the mesenteric lymph nodes to the liver and [[Spleen - Anatomy & Physiology|spleen]]
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*''[[Yersinia enterocolitica]]''
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**Pathogen of animals and humans
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**Found in intestinal tract and oral cavity of animals, eg. pigs, leading to infection of humans via contaminated carcasses
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**Enterocolitis in man which lasts 2-3 weeks or develops into a chronic form
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**Enteric disease in farmed deer
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**Ileitis, gastroenteritis, mesenteric adenitis
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**Pathogenicity related to a heat stable enterotoxin
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===Diagnosis===
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*''Yersinia'' species grow on blood agar and MacConkey agar at room temperature.
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*''Y. pseudotuberculosis'' and ''Y. enerocolica'' are motile, unlike ''Y. pestis''
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*Biochemical tests to identify particular species
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*Specific fluorescent antibody staining of lymph node aspirates to identify ''Y. pestis''
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 +
 
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===Control===
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*Control ''Y. pestis'' by controlling rodent population and flea control of cats
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*Control of other ''Yersinia'' species difficult due to their ubiquity
 +
 
 +
 
 +
===Treatment===
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*Euthanase or isolate animals suspected of ''Y. pestis'' infection; Streptomycin, doxycycline, gentamicin or chloramphinol
 +
*Long-acting tetracyclines, trimethoprim-sulphonamides, aminoglycosides and chloramphicol effective against ''Y. pseudotuberculosis'' and ''Y. enterocolica''

Revision as of 13:37, 12 May 2010


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BACTERIA



Overview


Characteristics

  • Enterobacteria, but grow more slowly and at lower temperatures than other enterobacteria
  • Gram negative, non-spore forming, facultative anaerobes - rods or colibacilli
  • Non-lactose fermentors
  • Facultative intracellular pathogens
  • Show bipolar staining in Giemsa-stained smears from animal tissue
  • Pathogenic strains identified by serotyping and biotyping


Pathogenesis

  • Y. enterocolitica and Y. pseudotuberculosis enter the intestinal mucosa via M cells of the Peyer's patches
  • Engulfed by macrphages in the mucosa
  • All three invasive species are facultative intracellular organisms and grow inside macrophages
  • Plasmid and chromosomal-encoded virulence factors required for survival and multiplication in macrophages
  • Survive in phagolysosomes and do not interfere with degranulation or lysosomal fusion
  • Resistant to macrophage killing mechanisms
  • Antiphagocytic proteins secreted by the organisms interfere with host neutrophils
  • Y. pestis is more invasive than the other species and also possesses and antiphagocytic capsule and a plasminogen activator which aids systemic spread; endotoxin also contributes to its pathogenicity
  • Transport within macrophages to mesenteric lymph nodes
  • Replication in lymph nodes and development of necrotic lesions, with neutrophil invasion
  • The bacteria destroy the macrophages causing septicaemia


Clinical infections

  • Yersinia pseudotuberculosis
    • Less virulent than Y. pestis but closely related
    • Mainly infect animals
    • One plasmid, required for virulence
    • Sporadic cases of pseudotuberculosis in animals and man
    • Wild birds and rodents provide a reservoir of infection by harbouring the the pathogen in their intestinal tract
    • Sources include food and water contaminated by faeces
    • Pseudotuberculosis (caseous abscesses) in rodents, guinea pigs, cats, turkeys
    • Epidymo-orchitis in rams
    • Abortion in goats
    • Occasional infections in pigs, cattle, sheep
    • Multiplication in macrophages leads to granuloma formation
    • Granulomas occur in the gut wall and mesenteric lymph nodes
    • Occasional spread from the mesenteric lymph nodes to the liver and spleen
  • Yersinia enterocolitica
    • Pathogen of animals and humans
    • Found in intestinal tract and oral cavity of animals, eg. pigs, leading to infection of humans via contaminated carcasses
    • Enterocolitis in man which lasts 2-3 weeks or develops into a chronic form
    • Enteric disease in farmed deer
    • Ileitis, gastroenteritis, mesenteric adenitis
    • Pathogenicity related to a heat stable enterotoxin


Diagnosis

  • Yersinia species grow on blood agar and MacConkey agar at room temperature.
  • Y. pseudotuberculosis and Y. enerocolica are motile, unlike Y. pestis
  • Biochemical tests to identify particular species
  • Specific fluorescent antibody staining of lymph node aspirates to identify Y. pestis


Control

  • Control Y. pestis by controlling rodent population and flea control of cats
  • Control of other Yersinia species difficult due to their ubiquity


Treatment

  • Euthanase or isolate animals suspected of Y. pestis infection; Streptomycin, doxycycline, gentamicin or chloramphinol
  • Long-acting tetracyclines, trimethoprim-sulphonamides, aminoglycosides and chloramphicol effective against Y. pseudotuberculosis and Y. enterocolica