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Concepts of Disease > Salmonellosis > Flashcards

Salmonellosis Flashcards

1
Q

What is salmonella?

A

Acute diarrohea infection caused by ingestion of food contaminated with bacterium belonging to genus Salmonella

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2
Q

What are the clinical symptoms of salmonella?

(4 marks)

A
  • Stomach cramp
  • Watery diarrhea
  • Fever
  • Vomiting
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3
Q

Why can there be some peaks seen across the average of Salmonella infections in europe?

A
  • Increase in temperature in summer
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4
Q

Is salmonella gram negative or gram positive bacteria?

A

Gram negative

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5
Q

What species of salmonella affects humans?

A

Salmonella enterica

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6
Q

What is a serotype?

(4 marks)

A
  • Group with single species of micro-organisms that share distinctive surface features i.e. bacteria/virus
  • O antigens are distinguished by different chemical makeup
  • H antigens are distinguished by protein content of the flagella
  • Each H and O antigen has a unique code number
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7
Q

What are some of the subspecies of S. enterica?

(3 marks)

A
  • Enterica (I)
  • Salamae (II)
  • Indica (VI)

3 More on slide/ notes

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8
Q

What are the top five serotypes of S. enterica that are responsible for human disease?

(5 marks)

A
  • S. Enteritidis
  • S. Typhimurium
  • S. Infantis
  • S. Stanley
  • S. Newport
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9
Q

What agar’s can be used to indentify S. enterica?

(2 marks)

A
  • Gram negative bacterium so use:
  • Xylose-lysine deoxycholate agar (XLD)
  • Brilliant green agar (BGA)

XLD on left

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10
Q

What happens once salmonella is put onto XLD agar?

(4 marks)

A
  • Ferments xylose
  • In fermentation, acidifies plate becoming yellow
  • After xylose completely used up, only salmonella able to decarboxylate lysine in middle so media turns red (alkalisation)
  • Salmonella metabolises thiosulfate so get production of hydrogen sulfide (black colony on middle image)

E.g. is middle image - alkalisation in B and acidification in C

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11
Q

What is a faculative anaerobe?

(2 marks)

A
  • Organism that makes ATP by aerobic respiration if oxygen is present,* but capable of *switching to fermentation is oxygen isn’t present
  • e.g. Salmonella enterica - spread across test tube but will gather mostly at the top because aerobic respiration generates more ATP than fermentation (right tube)
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12
Q

What process (more so molecular) can be used to identify the exact serovar in S. enterica?

A
  • Agglutination of polyvalent O and H
  • Then carry out biochemical tests of Oxidase and Indole tests
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13
Q

What does an oxidase test determine?

(2 marks)

A
  • Used to identify bacteria that produce cytochrome c
  • Can be used to identify gram negative bacili
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14
Q

What is the indole test used to determine?

(2 marks)

A

Dertermines if an organism has the ability to split amino acid tryptophan to form indole - positive test is indicated by red colour

For both gram positive and gram negative bacteria

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15
Q

What are zoonoses?

(2 marks)

A

Any disease or infection that is naturally transmissable from vertebrate animals to humans

May be bacterial or parasitic or may involve unconventional agents

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16
Q

What are food borne diseases?

(2 marks)

A
  • Result of ingestion of food stuffs - contaminated with micro-organisms or chemicals
  • Contamination can occur at any stage in process - can result from environmental contamination
  • Including pollution of water, soil or air
17
Q

What are ways of controlling Salmonella infections?

(3 marks)

A
  • Rehydration - lots of fluids
  • Manage fever - paracetamol
  • Antibiotics - NO - except if bacteria reach blood streams or compromised immune system
18
Q

Why isn’t loperamide used in controlling bacterial infections?

A

Prolongs diarrhea

19
Q

What do the S. Tyhpimurium virulance factors do?

(4 marks)

A
  • Aid in host colonisation
  • Allows immune evasion
  • Host/ predator destruction
  • Nutrient scavenging
20
Q

How does Salmonella infect the cell?

(2 marks)

A
  • Invades either M cell or apical domain of epithelial cells
  • Will cross and start to replicate inside host - either epithelial cell or M cell
21
Q

What are M cells and what is their structure and function?

(6 marks)

A
  • Microfold (M) cell
  • Concentrated in bigger part of small intestine
  • Phagocytes
  • Basolateral pocket at its base w/ a macrophage next to it
  • Everything absorbed by M cell is put into macrophage
  • Salmonella bypasses^^ to get into macrophage
22
Q

How does the T3SS work in Salmonellosis?

(5 marks)

A
  • 2 parts
  • Spi 1:
    • Bacteria in contact with non-phagocytic host cell, then forms injectosome and translocates forming pore in membrane
    • Effector protein activates Cdc42, Rac & RhoG by mimicking function and exploiting them to enter cell
  • After time passed bacteria inside express Spi 2 - works in exact same way as Spi 1 - uses own effector SifA to disrupt SCV
23
Q

Formation of which structure leads to cell invasion?

A

Macropinocytic membrane - extension is loosely attatched to bacteria which eventually leads to bacterial internalisation

24
Q

How does bacterial proliferation occur?

A
  • Bacteria goes further inside and forms serovar containing vacule:
  1. SCV recognised by host cell destroyed xenophagy
  2. Or bcteria escapes vacuole, goes to cytoplasm but v inefficient, most of time bacteria detected and destroyed by host
  3. Most of time have maturation of SCV towards Golgi network & in golgi network will express Spi 2 protein
  4. Forms tubular domain creates a niche where bacteria will replicate a lot and eventually kill macrophage before infecting next one
25
Q

What happens when S. Typhimurium is detected?

(5 marks)

A
  • Macrophage detect protein
  • Induces secretion of IL-8 and IL-23T
  • Cytokine induces recruitment of T-cell/ B-cell and neutrophils (neutrophils destroy bacteria)
  • Neutrophil destroy macrophage infected and secrete cytokines
  • i.e. IL-22 which increases production of antimicrobial peptides which will destroy bacteria in lumen before it can invade epithelial cells

Concepts of Disease (20 decks)

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