Cell Structures - Virulence Factors And Toxins Flashcards

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0
Q

What kinds of flagella can bacteria have?

A
  1. Single polar flagellum : Vibrio cholera.
  2. Many peritrichous flagella all around the cell : E.coli and Proteus mirabilis.
  3. Periplasmic flagella : spirochetes.
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1
Q

What is the structure by which the flagellum is affixed to the bacteria?

A

By a basal body, which spans through the entire cell wall, binding to the inner and outer cell membrane in gram negative bacteria and to the inner membrane in gram-positive bugs (the gram-positive bacteria don’t have an outer membrane).

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2
Q

Does shigella have flagella?

A

No!

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3
Q

What are the Pili (also called fimbriae)?

A
  1. Straight filaments arising from the bacterial cell wall, making the bacterium look like a porcupine.
  2. They are much shorter than flagella and do not move.
  3. Serve as adherence factors - adhesins.
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4
Q

Mention some bacteria that have pili and utilize them as adhesins.

A
  1. Neisseria gonorrhea : pili that allow it to bind to cervical cells and buccal cells to cause gonorrhea.
  2. E. coli + Campylobacter jejuni cannot cause diarrhea without their adhesins to bind to the intestinal epithelium.
  3. Bordetella pertussis uses its adhesin to bind to ciliated respiratory cells and cause whooping cough.
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5
Q

What are the components of the bacterial capsule?

A

They are usually composed of simple sugar residues.

Bacteria secrete these sugar moieties, which then coat their outer wall.

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6
Q

What is unique about Bacillus anthracis’ capsule?

A

It is made up of amino acid residues.

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7
Q

What is the main significance of a bacterial capsule?

A

Capsules enable bacteria to be more virulent because macrophages and neutrophils are unable to phagocytize the encapsulated buggers. (e.g. Streptococcus pneumoniae)

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8
Q

What are the two important tests that enable doctors to visualize capsules under the microscope and aid in identifying bacteria?

A
  1. India ink stain : the capsule appears as a transparent halo around the cell. (used primarily to identify the fungus Cryptococcus)
  2. Quelling reaction : bacteria are mixed with antibodies that bind to the capsule.
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9
Q

What contains a vaccine against streptococcus pneumoniae?

A

Antigens from the 23 most common types of capsules.

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10
Q

What are the two genera of bacteria that form endospores?

A
  1. The aerobic Bacillus
  2. The anaerobic Clostridium
    Both gram positive.
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11
Q

What are the components of the endospores multilayer?

A
  1. A cell membrane
  2. A thick peptidoglycan mesh
  3. Another cell membrane
  4. A wall of keratin-like protein
  5. An outer layer called the exosporium
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12
Q

What is a biofilm?

A

An extracellular polysaccharide network, similar to the capsule polysaccharides, that forms a mechanical scaffold around bacteria. It allows them to bind to prosthetic devices, like IV catheters, and protects them from attack by antibiotics and the immune system.

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13
Q

What is the main action of facultative intracellular organisms?

A

These bacteria inhibit phagosome-lysosome fusion.

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14
Q

Mention 8 important facultative intracellular organisms.

A
  1. Listeria monocytogenes
  2. Salmonella typhi
  3. Yersinia
  4. Francisella tularensis
  5. Brucella
  6. Legionella
  7. Mycobacterium
  8. Nocardia
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15
Q

Describe briefly what the exotoxins are.

A

Proteins released by both gram positive and gram negative bacteria.

16
Q

What diseases can exotoxins cause?

A
  1. Anthrax
  2. Botulism
  3. Tetanus
  4. Cholera
17
Q

What are the neurotoxins?

A

Exotoxins that act on the nerve or motor endplates to cause paralysis. Tetanus toxin and botulinum toxin are examples.

18
Q

What are the enterotoxins?

A

Exotoxins that act on the GI tract to cause diarrhea.

19
Q

What are the main actions of enterotoxins?

A
  1. Inhibit NaCl resorption
  2. Activate NaCl secretion
  3. Kill intestinal epithelial cells
    Common end result : the osmotic pull of fluid into the intestine, which causes diarrhea.
20
Q

What are the two diseases caused by enterotoxins?

A
  1. Infectious diarrhea

2. Food poisoning

21
Q

Mention some bacteria that can cause infectious diarrhea.

A
  1. Vibrio cholera
  2. Escherichia coli
  3. Campylobacter jejuni
  4. Shigella dysenteriae
22
Q

Mention some bacteria that cause food poisoning.

A
  1. Bacillus cereus

2. Staphylococcus aureus

23
Q

What are the pyrogenic exotoxins?

A

Stimulate the release of cytokines and can cause rash, fever, and toxic shock syndrome.

24
Q

Mention 2 bacteria that can release pyrogenic exotoxins.

A
  1. Staphylococcus aureus

2. Streptococcus pyogenes

25
Q

What are the tissue invasive exotoxins?

A

Exotoxins that allow bacteria to destroy and tunnel through tissues.
These include enzymes that destroy DNA, collagen, fibrin, NAD, RBCs, and WBCs.

26
Q

What are the exotoxin subunits in Bacillus anthracis, Clostridium botulinum, Clostridium tetani, Corynebacterium diphtheriae, and Vibrio cholera?

A

Composed of 2 polypeptide subunits bound together by disulfide bridges.

27
Q

How are the two subunits of exotoxin called?

A

One is called B for binding of H for holding : binds to the target cell.
The other subunit called A for action or L for laser : enters the cell and exerts the toxic effect.

28
Q

Why sometimes treating a patient who has a gram negative infection with antibiotics can worsen the things?

A

Because all the bacteria are lysed, releasing large quantities of endotoxin.

29
Q

How is endotoxin different from exotoxin?

A

Endotoxin differs from exotoxin in that it is not a protein excreted from cells, but rather is a normal part of the outer membrane that sort of sheds off, especially during lysis.

30
Q

What bacteria can cause septic shock?

A

Both gram positive and gram negative.

31
Q

What is the different between bacteremia and sepsis?

A

Bacteremia : bacteria in the blood-stream.

Sepsis : bacteremia that causes a systemic response to the infection.

32
Q

Mention 4 bacteria that produce exotoxins that increase levels of cAMP.

A
  1. Vibrio cholera
  2. Bacillus anthracis
  3. E.coli (Montezuma’s revenge)
  4. Bordetella pertussis