Difference between revisions of "Salmonella"
Jump to navigation
Jump to search
(44 intermediate revisions by 5 users not shown) | |||
Line 1: | Line 1: | ||
− | + | <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> | ||
+ | |||
===Overview=== | ===Overview=== | ||
*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) | ||
*''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 | ||
− | |||
===Characteristics=== | ===Characteristics=== | ||
Line 16: | Line 17: | ||
*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 | ||
− | |||
*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 | ||
− | |||
===Classification=== | ===Classification=== | ||
Line 32: | Line 31: | ||
*Single species, ''Salmonella enterica'' | *Single species, ''Salmonella enterica'' | ||
*Over 2400 pathogenic serotypes or serovars identified | *Over 2400 pathogenic serotypes or serovars identified | ||
− | *Grouped into 9 groups according to | + | *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 ( | + | *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=== | |
− | === | ||
*Faecal-oral transmission | *Faecal-oral transmission | ||
− | |||
− | |||
*Comparitively large dose required for infection due to gastric acid, normal intestinal flora and local immunity | *Comparitively large dose required for infection due to gastric acid, normal intestinal flora and local immunity | ||
*Enterocolitis: | *Enterocolitis: | ||
**Acute enteritis | **Acute enteritis | ||
− | **Bacteria | + | **Bacteria multiply in the intestine and damage epithelial cells |
− | + | **Cytotoxin may cause epithelial cell damage | |
− | **Cytotoxin may cause epithelial cell damage | ||
**Enterotoxin may induce fluid secretion into intestinal lumen | **Enterotoxin may induce fluid secretion into intestinal lumen | ||
**Degeneration of microvilli | **Degeneration of microvilli | ||
*Systemic disease: | *Systemic disease: | ||
− | + | **Bacteria internalised by intestinal epithelial cells | |
− | **Bacteria internalised by intestinal epithelial | ||
− | |||
**Stimulate immune response on reaching the lamina propria | **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 | **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 | **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 | ||
Line 70: | Line 56: | ||
**''Salmonellae'' can persist in the gut or gall bladder | **''Salmonellae'' can persist in the gut or gall bladder | ||
**Excreted in faeces after clinical signs disappeared - active carriage | **Excreted in faeces after clinical signs disappeared - active carriage | ||
− | **Bacteria can survive intracellularly, | + | **Bacteria can survive intracellularly, avioding the immune system and antimicrobials |
**May have latent carriage and intermittent excretion in faeces | **May have latent carriage and intermittent excretion in faeces | ||
− | ** | + | **Stress promotes excretion in carrier animals |
**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 |
+ | |||
===Clinical infections=== | ===Clinical infections=== | ||
*Zoonotic | *Zoonotic | ||
+ | *Outbreaks from contaminated imported meat and bone meal | ||
+ | *Some serotypes are host-specific, some are not | ||
+ | *''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 | *Most human infections contracted from animals, especially poulty and cattle | ||
− | * | + | *A cause of [[Intestines - Ulcerative Enteritis|ulcerative enteritis]] in the pig. |
− | + | *[[Intestines - Fibrinous/ Haemorrhagic Enteritis#Salmonellosis|Salmonellosis]] | |
− | + | *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]] | |
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | * | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | * | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
===Diagnosis=== | ===Diagnosis=== | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
===Treatment=== | ===Treatment=== | ||
− | |||
− | |||
− | |||
− | |||
===Control=== | ===Control=== | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
− |
Revision as of 19:21, 16 February 2008
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
- Faecal-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 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
- 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, avioding the immune system and antimicrobials
- May have latent carriage and intermittent excretion in faeces
- Stress promotes excretion in carrier animals
- 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 are not
- 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
- A cause of ulcerative enteritis in the pig.
- Salmonellosis
- Can cause haemorrhagic disease by secondary thrombocytopenic disease.
- Salmonella in Osteomyelitis
- In arthritis of horses