Ch. 15 Microbial Methods of Pathogenicity

Question 1

Pathogenicity

Answer 1

Ability to cause disease and overcome defences of host

Question 2

Virulence:

Answer 2

Degree of pathogenicity

Question 3

Portal of entry

Answer 3

how microbes enter. mucous membranes. Skin. parenteral route. Each microbe has a preferred entry.

Question 4

Number of invading microbes and ability to adhere to cells

Answer 4

Depends of what disease

Question 5

LD50 is

Answer 5

The number of pathogens that cause death in 50% of test animals

Question 6

ID50 is

Answer 6

the infectious dose that causes illness in test animals

Question 7

To cause infection the pathogen has to…

Answer 7

bind to cells. It depends how able it is to attach to cells.

Question 8

Adhesin

Answer 8

A term for what helps pathogens bind to cells. Ligands are often used for this.

Question 9

Biofilms

Answer 9

Help bacteria adhere better to tissue and makes them more likely to be pathogenic

Question 10

Penetration or evasion of host defenses – Capsule

Answer 10

Helps organisms stick or be “slick” enough to evade phagocytes

Question 11

Cell wall components

Answer 11

help bacteria evade capture. Exp: M proteins

Question 12

Enzymes

Answer 12

many. Some can digest blood clots or cellular material

Question 13

Antigenic variation:

Answer 13

Changes in the proteins on the surface of a bacteria that help the cell evade the immune response

Question 14

Invasins

Answer 14

Proteins that help the bacteria invade the cell. They promote entry in the initial stage of infection.

Question 15

Damage to host cells - siderophores

Answer 15

steal iron from tissues thus damaging tissues and the system

Question 16

Direct damage

Answer 16

Lytic cycle example where the cell bursts (lyses)

Question 17

Toxins

Answer 17

Some bacteria produce toxins, others don’t

Question 18

EXOTOXINS - details, and produced by?

Answer 18

Gram-pos or Gram-neg. Proteins that are secreted during the log phase to illicit a very specific effect.

Question 19

Exotoxins are

Answer 19

Heat sensitive and they cause disease that is called intoxication.

Question 20

Lysogenic conversion

Answer 20

Genes carried on plasmids or prophages integrate with otherwise harmless cell, and now the cell is able to create toxins (or other abilities) and be pathogenic.

Question 21

Exotoxin producing bacteria to remember –>

Answer 21

1. S. Pyogenes. Causes scarlet fever. Arithrogenic toxin. can cause infection after a Strept throat
2. Corynebacterium diptheriae. Causes Diptheria.
3. C. Botulinum. Causes botulism.
4. V. Cholorae. Causes cholera.

Question 22

A-B Toxin from an exotoxin – steps

Answer 22

1. Bacterium produces and releases A-B toxin.
2. B complex binds to cell receptor
3. Host cell invaginates whole toxin (A + B). Via ligand receptors (its a ligand imposter)
4. A & B separate. A is the active part of the complex, and it is the part that hurts you and does a specific effect.
5. B is released from cell. A does its thing free of the membrane that invaginated it.

Question 23

Toxoid

Answer 23

A vaccine for toxins. Makes toxin moiety turn into antigenic determinoids. Exp –> tetanus shot.

Question 24

Antitoxin

Answer 24

Blocks attachment of toxin. Antibody basically. It is temporary however, and it is used for when someone has a puncture wound for example. It just neutralizes the toxins being produced.

Question 25

Endotoxins

Answer 25

Lipids (not proteins!!!) that are made only from gram-negative bacteria. They are located in the outer membrane. Lipid A is an endotoxin.

Question 26

Endotoxin process – steps q

Answer 26

1. Macrophage ingests debris or cell
2. Lipid A –> causes phage to make cytokines (IL - 1) and (TNF-a)
3. Cytokines released through blood, eventually enter the brain at the hypothalamus.
4. Cytokines tell hypothalamus that “we are too cold” and so it produces prostaglandins which raise the “set point”. It induces a fever.

Question 27

Table 15.3 details of toxins

Answer 27

• gram-neg do endo and exo
• Lipid A = inflammation
• Small dose of exotoxin is bad

Question 28

Cytopathic effects

Answer 28

Effects other than death. Viruses do this. Exp: Clumping of cells thus decreasing function.

Question 29

Exit portal

Answer 29

Same as portal of entry typically. Unless GI. mouth to anus.