Difference between revisions of "Salmonella"
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*Important member of the enterobacteria | *Important member of the enterobacteria | ||
*Cause disease in humans and animals | *Cause disease in humans and animals | ||
| − | |||
*Reservior of infection in poulty, pigs, rodents, cattle, dogs | *Reservior of infection in poulty, pigs, rodents, cattle, dogs | ||
*Cause enteritis and systemic infection (septicaemia and abortion) | *Cause enteritis and systemic infection (septicaemia and abortion) | ||
| Line 35: | Line 34: | ||
===Characteristics=== | ===Characteristics=== | ||
| + | *Gram negative bacilli | ||
*Facultative intracellular pathogens | *Facultative intracellular pathogens | ||
| − | *Non-lactose fermentor | + | *Non-lactose fermentor, oxidase negative |
*Do not produce urease or indole from tryptophan | *Do not produce urease or indole from tryptophan | ||
| − | * | + | *Utilise citrate as a carbon source |
| + | *Reduce nitrates to nitrites | ||
| + | *Grow on MacConkey | ||
| + | *Ferment glucose to produce acid and gas | ||
*Usually produce hydrogen sulphide | *Usually produce hydrogen sulphide | ||
*Most motile with flagellae (H antigen) | *Most motile with flagellae (H antigen) | ||
| − | *H antigen can be in phase 1 or phase 2, depending on a genetic switch allowing for one of the H antigen genes to be transcribed | + | *H antigen can be in phase 1 or phase 2, depending on a genetic switch allowing for one of the H antigen genes to be transcribed at any one time |
===Classification=== | ===Classification=== | ||
| Line 52: | Line 55: | ||
===Pathogenesis=== | ===Pathogenesis=== | ||
| + | *Faemcal-oral transmission | ||
| + | *Comparitively large dose required for infection due to gastric acid, normal intestinal flora and local immunity | ||
| + | *Enterocolitis: | ||
| + | **Acute enteritis | ||
| + | **Bacteria multiply in the intestine and damage epithelial cells | ||
| + | **Cytotoxin may cause epithelial cell damage | ||
| + | **Enterotoxin may induce fluid secretion into intestinal lumen | ||
| + | **Degeneration of microvilli | ||
| + | *Systemic disease: | ||
| + | **Bacteria invade the body | ||
| + | **Bacteria internalised by intestinal epithelial cells | ||
| + | **Stimulate immune response on reaching the lamina propria | ||
| + | **Inflammatory response with phagocytosis of bacteria by neutrophils and macrophages | ||
| + | **Bacteria either destroyed by the phagocytic cells or survive and multiply in the cells to cause systemic disease | ||
| + | **Intracellular carriage if bacteria no completely removed | ||
===Clinical infections=== | ===Clinical infections=== | ||
Revision as of 18:44, 16 February 2008
- Some serotypes tend to be more species specific, whereas others can affect a wide range of species. For example:
- Salmonella enteritidis
- Salmonella typhimurium
- Widespread in most species.
- Salmonella dublin
- Cattle
- Salmonella cholerae suis
- Pigs
- Usually speticaemic.
- A cause of ulcerative enteritis in the pig.
- Not very common now.
- Salmonella montevideo
- Produces outbreaks from contaminated imported meat and bone meal.
- Salmonellosis
- * Can cause haemorrhagic disease by secondary thrombocytopenic disease.
- Salmonella in Osteomyelitis
- In arthritis of horses
Overview
- Important member of the enterobacteria
- Cause disease in humans and animals
- Reservior of infection in poulty, pigs, rodents, cattle, dogs
- Cause enteritis and systemic infection (septicaemia and abortion)
- Salmonella may be carried sub-clinically
- Some human strains cause enteric fever (S. Typhi causes typhoid), also gastroenteritis, septicaemia or bacteraemia
Characteristics
- Gram negative bacilli
- Facultative intracellular pathogens
- Non-lactose fermentor, oxidase negative
- Do not produce urease or indole from tryptophan
- Utilise citrate as a carbon source
- Reduce nitrates to nitrites
- Grow on MacConkey
- Ferment glucose to produce acid and gas
- Usually produce hydrogen sulphide
- Most motile with flagellae (H antigen)
- H antigen can be in phase 1 or phase 2, depending on a genetic switch allowing for one of the H antigen genes to be transcribed at any one time
Classification
- Single species, Salmonella enterica
- Over 2400 pathogenic serotypes or serovars identified
- Grouped into 9 groups according to O antigen (lipopolysaccharide) by the Kauffmann-White scheme - determined by slide agglutination of the bacteria with specific antisera
- Categorised into serovars depending on and H (flagellar) antigen, e.g. Salmonella enterica subspecies enterica serovar Tymphimurium; must also determine phase of H antigen
Pathogenesis
- Faemcal-oral transmission
- Comparitively large dose required for infection due to gastric acid, normal intestinal flora and local immunity
- Enterocolitis:
- Acute enteritis
- Bacteria multiply in the intestine and damage epithelial cells
- Cytotoxin may cause epithelial cell damage
- Enterotoxin may induce fluid secretion into intestinal lumen
- Degeneration of microvilli
- Systemic disease:
- Bacteria invade the body
- Bacteria internalised by intestinal epithelial cells
- Stimulate immune response on reaching the lamina propria
- Inflammatory response with phagocytosis of bacteria by neutrophils and macrophages
- Bacteria either destroyed by the phagocytic cells or survive and multiply in the cells to cause systemic disease
- Intracellular carriage if bacteria no completely removed