Difference between revisions of "Yersinia"

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<br>
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===Overview===
 +
*Cause [[Intestine Pathogens - Pathology|intestinal disease]] in animals and are important zoonoses
 +
*10 species of which ''Y. pestis, Y. pseudotuberculosis and Y. enterocolitica'' are pathogenic to animals and humans; ''Y. pestis'' is the most pathogenic
 +
*Rodents provide a reservoir of ''Y. pestis'', which is the cause of human plague; fleas transmit the infection to other animals and humans
 +
*''Y. pseudotuberculosis and Y. enterocolitica'' reside in the intestine of domestic and wild animals and birds
 +
*Birds may cause mechanical transfer of the organisms
 +
 
 +
===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 pestis''
 +
**Cause of bubonic plague in humans, transmitted via fleas from infected rats
 +
**Not a significant veterinary disease
 +
**Disease in rats and other rodents similar to the disease in humans
 +
**Bubonic form can lead to the pneumonic form, which is highly contagious and usually fatal
 +
**Humans and domestic and wild animals incidental hosts
 +
**Plague has rarely been reported in dogs, cats, camels, elephants, deer
 +
**Cats can acquire the disease from ingesting dead rodents, and show lymphadenopathy and abscesses
 +
**Fever, lethargy, swelling and abscessation of lymph nodes particularly in head and neck region
 +
**50% mortality if not treated
 +
**Possesses 3 plasmids, 2 of which are unique to this species; these encode an endotoxin, and coagulase and fibrinolytic activity
 +
*''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 - Anatomy & Physiology|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''

Revision as of 11:08, 29 December 2008

 This article has been peer reviewed but is awaiting expert review. If you would like to help with this, please see more information about expert reviewing.


Infectious agents and parasitesWikiBugs Banner.png
BACTERIA



Overview

  • Cause intestinal disease in animals and are important zoonoses
  • 10 species of which Y. pestis, Y. pseudotuberculosis and Y. enterocolitica are pathogenic to animals and humans; Y. pestis is the most pathogenic
  • Rodents provide a reservoir of Y. pestis, which is the cause of human plague; fleas transmit the infection to other animals and humans
  • Y. pseudotuberculosis and Y. enterocolitica reside in the intestine of domestic and wild animals and birds
  • Birds may cause mechanical transfer of the organisms

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 pestis
    • Cause of bubonic plague in humans, transmitted via fleas from infected rats
    • Not a significant veterinary disease
    • Disease in rats and other rodents similar to the disease in humans
    • Bubonic form can lead to the pneumonic form, which is highly contagious and usually fatal
    • Humans and domestic and wild animals incidental hosts
    • Plague has rarely been reported in dogs, cats, camels, elephants, deer
    • Cats can acquire the disease from ingesting dead rodents, and show lymphadenopathy and abscesses
    • Fever, lethargy, swelling and abscessation of lymph nodes particularly in head and neck region
    • 50% mortality if not treated
    • Possesses 3 plasmids, 2 of which are unique to this species; these encode an endotoxin, and coagulase and fibrinolytic activity
  • 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
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