Salmonella & Shigella

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  • Created by: Rose
  • Created on: 21-05-14 14:52
Name two infections commonly caused by Salmonella
Diarrhoea, Enteric Fever
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Name two common infections caused by Shigella
Traveller's Diarrhoea, Dysentry
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Is Salmonella gram positive or negative?
Gram negative bacilli (Like E.coli)
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Is Salmonella oxidase negative or positive?
Negative
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Salmonella possesses the somatic __ and flagellar __ antigen
O ; H
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Is Salmonella a lactose fermenter?
Non-lactose fermenting
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Does Salmonella produce H2S
Yes, Salmonella produces H2S
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Which species of Salmonella is usually associated with infection?
Salmonella enterica
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Which two subspecies of Salmonella enterica cause gastroenteritis?
Typhimurium & Enteritidis
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Which two subspecies of Salmonella enterica cause typhoid/enteric fever??
Typhi & Paratyphi
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* Gastroenteritis *
* Gastroenteritis *
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What is the reservoir of Salmonella in gastroenteritis?
G.I. tracts of poultry, domestic animals, reptiles, eggs
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Mode of transmission?
Ingestion of contaminated food
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What is the infective dose?
10^3 colonies / ml
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Name one human risk factor
Drugs reducing gastric acid
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Incubation period?
12-72 hours
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When symptoms arise, what are they?
Diarrhoea, vomiting, fever
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In immunocompromised persons, infection with Salmonella may lead to?
Serious complications e.g. Bacteremia
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* Pathogenesis *
* Pathogenesis *
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How does salmonella adhere to the G.I. cells?
Type III secretion system, and fimbriae
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What does Salmonella do once endocytosed into the G.I. cell, leading to what?
Multiplies and kills host cell, which leads to symptoms
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* TLRs *
* TLRs *
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What does TLR stand for?
Toll like Receptor
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Where are TLRs present and what do they recognise?
Phagocytes ; Recognise specific microbial patterns e.g. LPS
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Binding of these microbial patterns leads to what?
Activation of intracellular pathways, cytokine release, recruitment of neutrophils
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* TYPHOID FEVER *
* TYPHOID FEVER *
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Reservoir of typhoid fever is?
Human : CAN BE INFECTED OR CARRIER
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M.O.T?
Ingestion of contaminated food
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Incubation?
7-14 days *much longer than in gastroenteritis*
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Symptoms?
Fever
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What are the three outcomes from infection?
1.Complete recovery ; 2. Asymptomatic carriage ; 3. Complications e.g. ulcers in intestine, meningitis, pneumonia, osteomyelitis
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What is different about S. enterica Typhi?
Can cause primary and secondary bacteremia
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How does S. Typhi cause secondary bacteremia?
Taken up by macrophages, transported to lymph nodes, gets into blood --> GALL BLADDER --> Secondary bacteremia
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How does carriage of S. Typhi occur?
Persistence in gall bladder
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Name one similarity between S. Typhi and S. Typhimurium
Both have a type III secretion system
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S. Typhimurium interacts with _____, S. Typhi does not
Toll like receptors 4 & 5
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What is the pathogenicity island in S. Typhi called?
SPI 7
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SPI 7 encodes ___, which aids in export of the capsular antigen (evading recognition by TLR4)
Vi
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Which protein, encoded by SPI 7, inhibits flagellin expression and thus evades recognition by TLR 5?
Tvi
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How dS. Typhi persist in the gall bladder?
Bacteria adheres to gallstones, form a biofilm OR multiplication inside gall bladder epithelial cells
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Which sample would be taken and tested for if S. Typhimurium was suspected? (Gastroenteritis)
*****
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Which sample would be taken and tested for if S. Typhi was suspected? (Typhoid Fever)
Blood
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How would gastroenteritis be managed?
No antibiotics as usually self-limiting, control source! (Reservoir)
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How would typhoid fever be managed?
Antibiotics given due to high mortality rate. Better food handling, isolation of person, maybe removal of gall bladder in cases of persistence
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* Shigella *
* Shigella *
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Is Shigella lactose fermenting?
No, Shigella is not lactose fermenting
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Does Shigella produce H2S?
No, Shigella does not produce H2S
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There are 4 species that commonly cause infection
There are 4 species that commonly cause infection
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Which species of Shigella is more serious and is associated with dysentry?
Shigella dysentriae (some strains produce Shiga toxin)
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How is Shigella dysentriae transmitted?
Person --> Person (*****/oral)
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* Infective dose is v. low *
* Infective dose is v. low *
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Outline the pathogenesis of a Shigella infection
Shigella enters M cell (have no microvilli) on G.I. tract, multiply inside these M cells and then infect neighbouring cells - gap junctions. Death of cells causes the symptoms.
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Diarrhoea is usually managed by _____, with exceptions of?
Fluids, with exceptions of Shigella dysentry, more severe symptoms. Antibiotics not given for STEC.
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Other cards in this set

Card 2

Front

Name two common infections caused by Shigella

Back

Traveller's Diarrhoea, Dysentry

Card 3

Front

Is Salmonella gram positive or negative?

Back

Preview of the front of card 3

Card 4

Front

Is Salmonella oxidase negative or positive?

Back

Preview of the front of card 4

Card 5

Front

Salmonella possesses the somatic __ and flagellar __ antigen

Back

Preview of the front of card 5
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