Difference between revisions of "Salmonella"
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| − | + | <big><center>[[Enterobacteriaceae|'''BACK TO ENTEROBACTERIACEAE''']]</center></big> | |
| + | <big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big> | ||
| + | <big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big> | ||
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===Overview=== | ===Overview=== | ||
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*''Salmonella'' may be carried sub-clinically | *''Salmonella'' may be carried sub-clinically | ||
*Some human strains cause enteric fever (''S. Typhi'' causes typhoid), also gastroenteritis, septicaemia or bacteraemia | *Some human strains cause enteric fever (''S. Typhi'' causes typhoid), also gastroenteritis, septicaemia or bacteraemia | ||
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===Characteristics=== | ===Characteristics=== | ||
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*Gram negative bacilli | *Gram negative bacilli | ||
*Facultative intracellular pathogens | *Facultative intracellular pathogens | ||
| − | *Non-lactose | + | *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 | *Utilise citrate as a carbon source | ||
*Reduce nitrates to nitrites | *Reduce nitrates to nitrites | ||
*Grow on MacConkey | *Grow on MacConkey | ||
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*Ferment glucose to produce acid and gas | *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 at any one time | *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 | ||
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===Classification=== | ===Classification=== | ||
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*Categorised into serovars depending on and H (Flagellar) antigen, e.g. ''Salmonella enterica'' subspecies ''enterica'' serovar Tymphimurium; must also determine phase of H antigen (isolates must be in phase 1 to be typed) | *Categorised into serovars depending on and H (Flagellar) antigen, e.g. ''Salmonella enterica'' subspecies ''enterica'' serovar Tymphimurium; must also determine phase of H antigen (isolates must be in phase 1 to be typed) | ||
*Most animal and human isolates in Groups B to E | *Most animal and human isolates in Groups B to E | ||
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===Pathogenicity=== | ===Pathogenicity=== | ||
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**Stimulate immune response on reaching the lamina propria | **Stimulate immune response on reaching the lamina propria | ||
**Acute inflammation, possibly with ulceration; prostaglandin and cytokine production by epithelial cells; enterotoxin production damaging mucosa | **Acute inflammation, possibly with ulceration; prostaglandin and cytokine production by epithelial cells; enterotoxin production damaging mucosa | ||
| − | **Phagocytosis of bacteria by | + | **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 | **Bacteria either destroyed by the phagocytic cells or survive and multiply in the cells to cause systemic disease | ||
**Resistance to phagocytosis and destruction by complement allows spread within the body - bacteraemia and septicaemia | **Resistance to phagocytosis and destruction by complement allows spread within the body - bacteraemia and septicaemia | ||
**LPS O antigens prevent damage to bacterial cell wall by complement | **LPS O antigens prevent damage to bacterial cell wall by complement | ||
**LPS also causes endotoxaemia, and may contribute to local inflammatory response damaging intestinal cells to cause diarrhoea | **LPS also causes endotoxaemia, and may contribute to local inflammatory response damaging intestinal cells to cause diarrhoea | ||
| − | **Endotoxic shock during septicaemic | + | **Endotoxic shock during septicaemic salmonellosis due to LPS |
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**Intracellular carriage if bacteria no completely removed | **Intracellular carriage if bacteria no completely removed | ||
| − | **Invasive potential of certain strains e. | + | **Invasive potential of certain strains e.e ''Salmonella'' Dublin associated with carriage of a large plasmid, encoding genes to allow intracellular survival in macrophages and also to allow iron acquisition |
**''Salmonellae'' are facultative intracellular organisms, allowing them to move from the gut in macrophages and cause a bacteraemia and lesions throughout the body | **''Salmonellae'' are facultative intracellular organisms, allowing them to move from the gut in macrophages and cause a bacteraemia and lesions throughout the body | ||
**Possession of Pathogenicity Islands associated with virulence | **Possession of Pathogenicity Islands associated with virulence | ||
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**Bacteria can survive intracellularly, avoiding the immune system and antimicrobials | **Bacteria can survive intracellularly, avoiding the immune system and antimicrobials | ||
**May have latent carriage and intermittent excretion in faeces | **May have latent carriage and intermittent excretion in faeces | ||
| − | **Stresses e.g. | + | **Stresses e.g. transportaion, illness, parturition, overcrowding promote excretion in carrier animals and may cause clinical signs to be shown |
**Tortoises, terrapins, snakes and other reptiles ofter carry ''Salmonellae'' | **Tortoises, terrapins, snakes and other reptiles ofter carry ''Salmonellae'' | ||
| − | **Asymptomatic carriage allows faecal spread of infection | + | **Asymptomatic carriage allows faecal spread of infection |
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===Clinical infections=== | ===Clinical infections=== | ||
*Zoonotic | *Zoonotic | ||
| − | * | + | *Outbreaks from contaminated imported meat and bone meal |
*Some serotypes are host-specific, some infect a wide range of species | *Some serotypes are host-specific, some infect a wide range of species | ||
| − | *Healthy adult carnivores are resistant to | + | *Healthy adult carnivores are resistant to salmonellosis |
*Clinical outcome depends on number of bacteria ingested, virulence of serotype, susceptibility of host | *Clinical outcome depends on number of bacteria ingested, virulence of serotype, susceptibility of host | ||
*Young and debilitated animals susceptible | *Young and debilitated animals susceptible | ||
| − | + | *''S.'' Tymphimurium infects many species; causes severe diarrhoea; non-invasive; causes of food poisoning in humans, e.g. from infected poultry | |
| − | + | *''S. enteritidis'': non species-specific; losses in young birds; causes food poisoning in humans | |
| − | + | *''S.'' Dublin: invasive serovar; infects cattle | |
| − | + | *''S.'' Cholerae-Suis: primarily infects pigs; also causes severe human disease | |
| − | + | *''S.'' Pullorum: infects poultry; egg-transmitted; causes bacillary white diarrhoea, known as pullorum disease | |
| − | + | *''S.'' Gallinarum: infectes older birds; known as howl typhoid | |
| − | + | *''S.'' Pullorum and ''S.'' Gallinarum now rare in UK due to eradication programs including the Pullorum test (whole blood slide agglutination to detect antibody to both ''S.'' Pullorum and ''S'' Gallinarum | |
| − | **''S.'' Abortis-ovis: infects sheep | + | *''S.'' Abortis-ovis: infects sheep |
| − | + | *''S.'' Abortus-equi: infects horses outside of the UK | |
| − | + | *''S.'' Typhi, ''S.'' Paratyphi: infect humans | |
| − | * | + | *Most human infections contracted from animals, especially poulty and cattle |
| − | + | *Enteric and septicaemic forms of salmonellosis | |
| − | + | *Bovine [[Intestines - Fibrinous/ Haemorrhagic Enteritis#Salmonellosis|Salmonellosis]]: | |
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| − | *Bovine [[Salmonellosis| | ||
**Syndrome of fever and diarrhoea (with dysentery), often fatal, in calves and adult cattle | **Syndrome of fever and diarrhoea (with dysentery), often fatal, in calves and adult cattle | ||
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**May cause abortion of pregnant cattle in absence of other signs | **May cause abortion of pregnant cattle in absence of other signs | ||
**Septicaemia in neonates; accute enteritis in older calves | **Septicaemia in neonates; accute enteritis in older calves | ||
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**Caused by infection with various ''Salmonella'' serotypes, e.g. ''S.'' Dublin and ''S.'' Typhimurium | **Caused by infection with various ''Salmonella'' serotypes, e.g. ''S.'' Dublin and ''S.'' Typhimurium | ||
| + | **Chronic infections with ''S.'' Dublin in calves cause dry gangrene and bone lesions | ||
**An important zoonosis and reportable | **An important zoonosis and reportable | ||
**Carrier animals important for spread | **Carrier animals important for spread | ||
| − | * | + | *A cause of [[Intestines - Ulcerative Enteritis|ulcerative enteritis]] in the pig. |
| − | + | *Can cause haemorrhagic disease by [[General Pathology - Haemostasis#Secondary Thrombocytopenic Disease|secondary thrombocytopenic disease]]. | |
| − | + | *''Salmonella'' in [[Bones - inflammatory#Osteomyelitis|Osteomyelitis]] | |
| − | + | * In [[Joints - inflammatory#In Horses|arthritis of horses]] | |
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===Diagnosis=== | ===Diagnosis=== | ||
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===Treatment=== | ===Treatment=== | ||
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===Control=== | ===Control=== | ||
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Revision as of 10:05, 17 February 2008
Overview
- Important member of the enterobacteria
- Cause disease in humans and animals worldwide
- Reservior of infection in poulty, pigs, rodents, cattle, dogs
- Bacteria may be present in water, soil, animal feed, raw meat
- 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 Somatic, 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 (isolates must be in phase 1 to be typed)
- Most animal and human isolates in Groups B to E
Pathogenicity
- Faecal-oral transmission
- Infection frequently transmitted from faeces of rodents and birds
- Young, immunocompromised animals particularly susceptible
- Comparitively large dose required for infection due to gastric acid, normal intestinal flora and local immunity
- Enterocolitis:
- Acute enteritis
- Bacteria adhere to intestinal epithelial cells in the ileum and colon, probably via fimbrae, O antigen and flagellar H antigen
- Multiply in and destroy epithelial cells
- Cytotoxin may cause epithelial cell damage by inhibiting protein synthesis and causing calcium escape from cells
- Enterotoxin may induce fluid secretion into intestinal lumen
- Degeneration of microvilli
- Systemic disease:
- Bacteria invade and replicate in host cells and resist phagocytosis and destruction by complement
- Bacteria internalised by intestinal epithelial cells by inducing ruffling of cell membranes and uptake into vesicles
- The organisms replicate within the vesicles and are released from the cells
- Stimulate immune response on reaching the lamina propria
- Acute inflammation, possibly with ulceration; prostaglandin and cytokine production by epithelial cells; enterotoxin production damaging mucosa
- 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
- Resistance to phagocytosis and destruction by complement allows spread within the body - bacteraemia and septicaemia
- LPS O antigens prevent damage to bacterial cell wall by complement
- LPS also causes endotoxaemia, and may contribute to local inflammatory response damaging intestinal cells to cause diarrhoea
- Endotoxic shock during septicaemic salmonellosis due to LPS
- Intracellular carriage if bacteria no completely removed
- Invasive potential of certain strains e.e Salmonella Dublin associated with carriage of a large plasmid, encoding genes to allow intracellular survival in macrophages and also to allow iron acquisition
- Salmonellae are facultative intracellular organisms, allowing them to move from the gut in macrophages and cause a bacteraemia and lesions throughout the body
- Possession of Pathogenicity Islands associated with virulence
- Carriage:
- Salmonellae can persist in the gut or gall bladder
- Excreted in faeces after clinical signs disappeared - active carriage
- Bacteria can survive intracellularly, avoiding the immune system and antimicrobials
- May have latent carriage and intermittent excretion in faeces
- Stresses e.g. transportaion, illness, parturition, overcrowding promote excretion in carrier animals and may cause clinical signs to be shown
- Tortoises, terrapins, snakes and other reptiles ofter carry Salmonellae
- Asymptomatic carriage allows faecal spread of infection
Clinical infections
- Zoonotic
- Outbreaks from contaminated imported meat and bone meal
- Some serotypes are host-specific, some infect a wide range of species
- Healthy adult carnivores are resistant to salmonellosis
- Clinical outcome depends on number of bacteria ingested, virulence of serotype, susceptibility of host
- Young and debilitated animals susceptible
- S. Tymphimurium infects many species; causes severe diarrhoea; non-invasive; causes of food poisoning in humans, e.g. from infected poultry
- S. enteritidis: non species-specific; losses in young birds; causes food poisoning in humans
- S. Dublin: invasive serovar; infects cattle
- S. Cholerae-Suis: primarily infects pigs; also causes severe human disease
- S. Pullorum: infects poultry; egg-transmitted; causes bacillary white diarrhoea, known as pullorum disease
- S. Gallinarum: infectes older birds; known as howl typhoid
- S. Pullorum and S. Gallinarum now rare in UK due to eradication programs including the Pullorum test (whole blood slide agglutination to detect antibody to both S. Pullorum and S Gallinarum
- S. Abortis-ovis: infects sheep
- S. Abortus-equi: infects horses outside of the UK
- S. Typhi, S. Paratyphi: infect humans
- Most human infections contracted from animals, especially poulty and cattle
- Enteric and septicaemic forms of salmonellosis
- Bovine Salmonellosis:
- Syndrome of fever and diarrhoea (with dysentery), often fatal, in calves and adult cattle
- May cause abortion of pregnant cattle in absence of other signs
- Septicaemia in neonates; accute enteritis in older calves
- Caused by infection with various Salmonella serotypes, e.g. S. Dublin and S. Typhimurium
- Chronic infections with S. Dublin in calves cause dry gangrene and bone lesions
- An important zoonosis and reportable
- Carrier animals important for spread
- A cause of ulcerative enteritis in the pig.
- Can cause haemorrhagic disease by secondary thrombocytopenic disease.
- Salmonella in Osteomyelitis
- In arthritis of horses