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Foundations of Medicine > Week 3 - Microbiology - Bacterial Pathogenesis and Host Defense > Flashcards

Week 3 - Microbiology - Bacterial Pathogenesis and Host Defense Flashcards

1
Q

Endotoxin

A

only in gram negative bacteria

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2
Q

Pathogen

A

bacteria capable of causing disease

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3
Q

Virulence

A

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

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4
Q

LD50

A

number of bacteria necessary to kill half the host

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5
Q

ID50

A

number of bacteria necessary to cause infection in half the hosts

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6
Q

Virulence Factors

A

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

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7
Q

What are the stages of bacterial pathogens

A
  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
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8
Q

**What types of viruses to know about

A

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

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9
Q

What are the three mechanisms of bacterial disease?

A
  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
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10
Q

What are transmission mechanisms

A

add

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11
Q

Human to human transmission

A

Direct contact eg infections mono

Non-direct contact eg. fecal-oral

Transplacental

Transferred blood products or contaminated needles

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12
Q

Non-human to human

A

Contaminated soils eg. Tetanus

Contaminated water eg. Legionnaires’ disease

Direct from animals eg. Cat Scratch fever

Insect vectors eg. Lyme disease

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13
Q

What are the four portals of entry

A

Respiratory tract (biggest portal!)

GI tract

Skin

Genital tract

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14
Q

Bacterial structures (virulence factors)

A 
Pili
Capsules
Glycocalyx
Endotoxin
Biofilms
Bacterial Secretion Systems
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15
Q

Secreted Enzymes (virulence factors)

A

Collagenase & hyaluronidase

Coagulase

Immunoglobulin A Protease

Leukocidins

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16
Q

Other bacterial factors of virulence

A

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…

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17
Q

Exotoxins

A

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

18
Q

What are 5 effects of exotoxins?

A 
Alter cellular components
Are superantigens
Inhibit protein synthesis
Increase synthesis of cAMP
Alter nerve impulse transmissions
19
Q

Type III cytotoxins

A

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.

20
Q

wer

A

Increase in cytokines has very bad effect on body..

21
Q

Diptheria toxin

A

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

22
Q

Endotoxins

A

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

23
Q

What are biological effects of endotoxins?

A

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.

24
Q

Components of host defenses

A

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

25
Q

Innate Immunity

A

Macrophages - phagocytize and digest bacteria

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

26
Q

What are two types of immunity

A

Innate and acquired

27
Q

Active immunity

A

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

28
Q

Passive Immunity

A

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

29
Q

Passive vs Active Immunity

A

we

30
Q

Some diseases have both passive and active

Some only active immunity

A

s

31
Q

Ways for bacteria to avoid the Innate Immune Response

A

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

32
Q

Avoiding IIR?

A

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).

33
Q

Avoiding engulfment (IIR)

A

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

34
Q

Intracellular survival of bacteira

A

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 ***

35
Q

Other methods of phogocytic or compliment avoidance by bacteria

A

we

36
Q

w

A

w

37
Q

w

A

w

38
Q

w

A

w

39
Q

Immunological Disguise

A

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

40
Q

Protein A

A

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..

41
Q

read pseudomonas paper..

A

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

Foundations of Medicine (42 decks)

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