Week 3 - Microbiology - Bacterial Pathogenesis and Host Defense

Question 1

Endotoxin

Answer 1

only in gram negative bacteria

Question 2

Pathogen

Answer 2

bacteria capable of causing disease

Question 3

Virulence

Answer 3

quantitative measure of pathogenicities measured by the number of bacteria required to cause disease

Question 4

LD50

Answer 4

number of bacteria necessary to kill half the host

Question 5

ID50

Answer 5

number of bacteria necessary to cause infection in half the hosts

Question 6

Virulence Factors

Answer 6

properties of a bacteria which assist in causing disease ex: pili, capsules, toxins, etc.

Question 7

What are the stages of bacterial pathogens

Answer 7

1. Transmission from an external source into the body
2. Evasion of initial host defenses
3. Attachment to mucous membranes
4. Colonization at attachment site
5. Sometimes spread and reattachment
6. Disease symptoms caused by toxins or tissue invasion followed by inflammation
7. Non specific and specific immune host responses
8. Progression or resolution of the disease

Question 8

**What types of viruses to know about

Answer 8

influenza.. retroviruses.. What he spent a lot of time on. Learning objectives**

Question 9

What are the three mechanisms of bacterial disease?

Answer 9

1. Tissue invasion followed by inflammation
2. Toxins (exotoxins (can be toxins that enter by food but no bacterial present.. bacteria produce tosxin in food then eat it.. food poisoning) and endotoxins (gram neg))
3. Immunopathogenesis eg. Rheumatic fever caused by specific bacteria

Question 10

What are transmission mechanisms

Answer 10

add

Question 11

Human to human transmission

Answer 11

Direct contact eg infections mono

Non-direct contact eg. fecal-oral

Transplacental

Transferred blood products or contaminated needles

Question 12

Non-human to human

Answer 12

Contaminated soils eg. Tetanus

Contaminated water eg. Legionnaires’ disease

Direct from animals eg. Cat Scratch fever

Insect vectors eg. Lyme disease

Question 13

What are the four portals of entry

Answer 13

Respiratory tract (biggest portal!)

GI tract

Skin

Genital tract

Question 14

Bacterial structures (virulence factors)

Answer 14

Pili
Capsules
Glycocalyx
Endotoxin
Biofilms
Bacterial Secretion Systems

Question 15

Secreted Enzymes (virulence factors)

Answer 15

Collagenase & hyaluronidase

Coagulase

Immunoglobulin A Protease

Leukocidins

Question 16

Other bacterial factors of virulence

Answer 16

M Protein

Protein A - binds to IgG adn prevents activation of complement

Invasions

Outer membrane proteins

Pathogenicity Islands (PAIs)* - in gram neg bacterial there are PAI of genetic material which code for virulence factors. If get rid of PAI - bacteria cant cause disease…

Question 17

Exotoxins

Answer 17

Polypeptides secreted by bacteria

If you can isolate the exotoxin and treat it with formaldyhol it can be used as vaccine - called a toxoid.

Two components A (toxic) & B (binding structure)

Exotoxins are coded on bacterial chromosom, plasmid, or phage

Question 18

What are 5 effects of exotoxins?

Answer 18

Alter cellular components
Are superantigens
Inhibit protein synthesis
Increase synthesis of cAMP
Alter nerve impulse transmissions

Question 19

Type III cytotoxins

Answer 19

Some bacteria have a type III cytotoxin

The bacterial use an injectosome to directly inject exotoxin into cell..

Normally, bodily antibodies inhibit B part of exotoxin so it cant get into cell.. however, in this case there is no B part adn body has difficulty fighting it.

Question 20

wer

Answer 20

Increase in cytokines has very bad effect on body..

Question 21

Diptheria toxin

Answer 21

If doesnt get on phage and to make cornebacterium diphtheria it wont cause disease.. if it does get to sit on phage, it will cause adp ribosylase elongation factor 2.. ?? idk anymore

Question 22

Endotoxins

Answer 22

Are integral parts of the cell wall of Gram negative rods and cocci

Involve the Lipid A component of lipopolysaccharide

Only weakly antigenic; no toxoids made

Induced biological effects focus on fever and shock

Question 23

What are biological effects of endotoxins?

Answer 23

Induce the release of endogenous pyogenes

Increase vascular permeability

Imitate complement and blood coagulation cascades

Cause fever, hypotension, disseminated intracellular coagulation and shock

Lipid A porting important.. ppl die from endotoxic shock.

Question 24

Components of host defenses

Answer 24

Acquired immunity - only occur after we get a foreign stimulus from pathogen

Antibodies

• cytoloytic
• neutralizing*
• opsonins

Cytotoxic T cells
-kill antibody coated bacteria and virus infected cells

Question 25

Innate Immunity

Answer 25

Macrophages - phagocytize and digest bacteria Complement - assist host immune cells and antibody in lysis of bacteria and virus infected cells

Question 26

What are two types of immunity

Answer 26

Innate and acquired

Question 27

Active immunity

Answer 27

Administration of specific antigens to stimulate an individual to develop immunity to help protect from a disease ex. Influenza vaccine

Question 28

Passive Immunity

Answer 28

Administration of preformed antigen-specific antibodies to help protect from disease ex. Human rabies immune globulin

Question 29

Passive vs Active Immunity

Answer 29

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Question 30

Some diseases have both passive and active | Some only active immunity

Answer 30

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Question 31

Ways for bacteria to avoid the Innate Immune Response

Answer 31

Dealing with phagocytes and complement: There are essentially three categories of bacterial strategies to deal with phagocytic cells: Avoiding contact with phagocytes Inhibition of engulfment Survival within the phagocyte

Question 32

Avoiding IIR?

Answer 32

The bacteria can reside in a niche not patrolled by phagocytes. The bacteria can suppress inflammation and/or chemotaxis. The bacterium can coat itself with host proteins (more later).

Question 33

Avoiding engulfment (IIR)

Answer 33

Many bacterial capsules are anti-phagocytic. Some surface polysaccharides (such as those that aid in biofilm structure) are anti-phagocytic. Some bacteria produce specific anti-phagocytic products. Capsules can inhibit phagocytosis and complement activation

Question 34

Intracellular survival of bacteira

Answer 34

Intracellular survival is mediated by bacteria in three basic ways: Escape the phagosome Shigella, Lysteria Adapt to the phagosome Coxiella, Leishmania Modify the phagosomal compartment Salmonella, Legionella, Mycobacteria, etc. Bacteria can avoid being killed ***

Question 35

Other methods of phogocytic or compliment avoidance by bacteria

Answer 35

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Question 36

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Answer 36

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Question 37

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Answer 37

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Question 38

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Answer 38

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Question 39

Immunological Disguise

Answer 39

Bacteria coat themselves with host proteins Disguised by “self” proteins – camouflage! E.g. proteins produced by some bacteria bind Antibodies – BACKWARDS!* - the body doesnt recognize the cell because its covered in its own antibodies

Question 40

Protein A

Answer 40

Staphylococcal virulence factor.. Staph synthesies proten A. Protein A binds IgG (immunoglobin) on the surface of the cell.. the immune system just sees IgG but not bact so it is disguised..

Question 41

read pseudomonas paper..

Answer 41

concept questions Case questions most difficult.. does a certain bacterial have a toxoid..