Difference between revisions of "Yersinia"
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| + | ===Overview=== | ||
| + | |||
| + | *Cause [[Intestines - disease due to pathogens|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 | ||
| + | |||
| + | ===Clnical 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 in 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 | ||
| + | **Multiplication in macrophages leads to granuloma formation | ||
| + | **Granulomas occur in the gut wall and mesenteric lymph nodes | ||
| + | |||
| + | ===Diagnosis=== | ||
| + | |||
| + | ===Control=== | ||
| + | |||
| + | ===Treatment=== | ||
Revision as of 13:52, 9 February 2008
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
Clnical 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 in 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
- Multiplication in macrophages leads to granuloma formation
- Granulomas occur in the gut wall and mesenteric lymph nodes