Difference between revisions of "Yersinia"

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#REDIRECT[[:Category:Yersinia species]]
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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


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