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Bacterial pathogenesis Flashcards

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0
Q

What is immune selection and what is an example?

A

Bacteria know our immune system better than we do so they use it for their benefit
Relapsing fever is driving force for antigenic variation in Borrelia hermsii

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1
Q

Pathogenic bacteria are often clonal. How do they differ from nonpathogenic bacteria?

A

They have additional virulence genes

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2
Q

Is antibiotic resistance more commonly selected in a population or individual?

A

Population

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3
Q

What are Koch’s postulates for?

A

Guidelines for establishing the cause of an infectious disease

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4
Q

What are Koch’s postulates?

A
  1. Microorganism found in all cases of disease and in right spot
  2. Microorganism can be grown outside the host for several generations
  3. Reinoculation of the cultivated microorganism causes the disease
  4. Microorganism can be isolated from experimentally produced disease
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5
Q

What are two examples of organisms that can’t be cultured?

A 
Treponema pallidum (syphilis) - use rabbit testes
Tropheryma whipplei (Wipple's disease) - use PCR
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6
Q

Name an organism that does not have an animal model?

A

Neisseria gonorrheae

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7
Q

Transmissibility: is it better to have a clinically mild or strong disease?

A

Clinically mild because a well adapted bug doesn’t want to kill its host

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8
Q

Why are there clinically symptomatic diseases?

A

Non-adapted host or pathogen (zoonotic bacteria)
Clinical symptoms that promote transmission
Disease manifestations that are due to host response to pathogen

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9
Q

5 ways that bacteria can spread in the body?

A 
Direct tissue spread
vascular
lymphatic
within macrophages
ascending/descending within body tracts
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10
Q

Extracellular bacteria often cause disease via the effect of?

A

Toxins and enzymes

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11
Q

Intracellular bacteria are able to do what?

A

Invade host cells and often cause chronic infections

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12
Q

What are exotoxins?

A

Highly toxic proteins secreted by bacteria into the extracellular environment
Often have two subunits (A and B)

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13
Q

What do the A and B subunits of exotoxins do?

A

A: active subunit with specific toxin activity
B: binds to specific host cell receptor; involved in entry of exotoxin into cell

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14
Q

Corynebacterium diptheriae is an example of what? What is the mechanism?

A

AB subunit exotoxin

Inhibition of protein synthesis, cell death

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15
Q

What is food poisoning commonly caused by?

A

staphylococcal enterotoxin or botulinum toxin

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16
Q

What is usually required for toxin production to occur?

A

Active bacterial infection

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17
Q

How does enterotoxin vibrio cholerae cause diarrhea?

A

It is an AB exotoxin that induces adenylate cyclase activity which increases cAMP which causes increased secretion of cell nutrients, causing diarrhea

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18
Q

How does neurotoxin clostridium tetani work?

A

It is a AB subunit exotoxin that blocks inhibitory nt release which causes continuous stimulation by the excitatory nt … causing spastic paralysis

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19
Q

How does the neurotoxin clostridium botulinum work?

A

AB exotoxin that blocks the release of ACH from vesicles which causes flaccid paralysis of muscles

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20
Q

How does bacillus anthracis work?

A

3 proteins make up 2 toxins
“protective antigen” is the B subunit
The A subunits are: edema factor (an adenylate cyclase) and lethal factor (kills cells)

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21
Q

superantigens vs exotoxins and fever?

A

Superantigens cause fever while exotoxins do not

Although some exotoxins are superantigens

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22
Q

What are superantigens produced by?

A

bacteria and viruses

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23
Q

How do superantigens work? Two examples?

A

Polyclonal stimulation of T cells to divide and produce cytokines
Staph Toxic Shock Syndrome Toxin-1
Strep exotoxins

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24
Q

What are pyrogenic toxins?

A

Cause fever unlike other exotoxins

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25
Q

Exotoxins are partially denatured by treatment with what? What does it create?

A

Formalin, acid, or heat

Creates a toxoid (nontoxic but still antigenic)

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26
Q

What are toxoids used for? 2 examples

A

Immunization

Diphtheria and tetanus toxoids

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27
Q

Exotoxins are highly _________ and _______ labile

A

highly antigenic

heat labile

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28
Q

Endotoxin is also known as what? It is an integral part of what?

A

LPS - lipopolysaccharide

Gram - bacteria cell wall

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29
Q

Describe the LPS cascade that causes septic shock

A

Endotoxin in the bloodstream binds to receptors on macrophages which signals a cytokine release which activates inflammatory and coagulation cascades

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30
Q

Septic shock can also be caused by gram + bacteria, even though they don’t have LPS… why?

A

Probably due to peptidoglycan even though it is less potent

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31
Q

What part of LPS is the toxic moiety?

A

Lipid A

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32
Q

Which is more toxic, LPS or exotoxin?

A

Exotoxin

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33
Q

Exotoxin: gram - or + ?

A

Both

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34
Q

Endotoxin: gram - or +?

A

gram -

35
Q

Exotoxin vs endotoxin, how are they released?

A

Exotoxin is secreted

Endotoxin is released once cell is lysed

36
Q

Which is more toxic, endotoxin or exotoxin?

A

Exotoxin

37
Q

Which is more antigenic, endotoxin or exotoxin?

A

Exotoxin

38
Q

Reaction to heat: endotoxin vs exotoxin

A

Endotoxin is heat table

Exotoxin is inactivated to form toxoid

39
Q

Which causes fever, endotoxin or exotoxin?

A

Endotoxin causes fever and septic shock

However pyrogenic toxins cause fever, and some exotoxins are pyrogenic

40
Q

Are all bacterial enzymes intrinsically toxic?

A

No

41
Q

How to bacterial enzymes cause tissue damage? What are they destroying?

A

Connective tissue

Also degrades hyaluronic acid (hyaluronidase)

42
Q

What is streptokinase?

A

Fibrinolysin - blood clots

43
Q

What is coagulase?

A

Coagulates plasma

44
Q

What is catalase?

A

Inhibits oxidative killing

Gram - don’t have

45
Q

What do cytolysins do?

A

Kill host cells

46
Q

What is Streptolysin S?

A

Group A beta-hemolytic streptococci

47
Q

What is the first step in entry to the host cell and secretion of bacterial proteins into the host cell?

A

Adherence to host cell

48
Q

Antibodies against what can block adhesion of bacteria to host cells?

A

Antibodies against adhesin

49
Q

What can cause pyelonephritis?

A

P pilus of E. coli

50
Q

What is the type III secretion system? Which bacteria type have it?

A

Used for secreting bacterial virulence proteins into host cells
Only in pathogenic gram -

51
Q

For the secretion of bacterial proteins into host cells, what are their two different functions?

A

induce/prevent uptake by mammalian cell

induce/prevent death of mammalian cell

52
Q

What is an example of a bacteria that induces uptake by a mammalian cell? One that prevents uptake?

A

Salmonella - invades mammalian cells

Yersinia - prevents phagocytosis by macrophages

53
Q

What is an example of a bacteria that induces cell death? One that prevents it?

A

Yersinia induces apoptosis of macrophages

Chlamydia prevents apoptosis (intracellular bacteria)

54
Q

What are three advantages of intracellular localization?

A

Nutrient rich environment
Absence of competing microorganisms
Protected from humoral immune system

55
Q

Intracellular bacteria that survives inside a phagolysosome?

A

Coxiella

56
Q

Intracellular bacteria that inhibits phagolysosomal fusion?

A

Chlamydia

57
Q

Intracellular bacteria that escapes into cytosol?

A

Listeria

58
Q

Diagram the intracellular life cycle of listeria

A 
Entry by internalin
Lysis of vacuole by listeriolysin O
Escape into cytosol
Actin based motility by ActA
Spread to adjacent cell
Lysis of vacuole... etc
59
Q

What bacteria absorbs normal host component to surface of itself to avoid host immune system?

A

Staphylococcus aureus (protein A binds IgG)

60
Q

What are 3 surface factors that inhibit phagocytosis?

A

Polysaccharide capsule
M protein: group A streptococci
Pili : neisseria gonorrheae

61
Q

Why does the polysaccharide capsule aid in evasion of host immune system?

A

Prevents complement deposition and is poorly immunogenic
Induces T cell independent immune response
Response is poor in children <2

62
Q

What are 3 bacteria that utilize the polysaccharide capsule to evade immune systems?

A

Bacteria that cause meningitis
neisseria meningetidis
streptococcus pneumoniae
haemophilus influenzae

63
Q

Are antibodies against polysaccharide capsular type general or specific? What do these antibodies protect against?

A

Have to be specific
Protect against serious systemic infection
Do not protect against mucosal colonization

64
Q

Example of 2 bacteria that switch surface antigens?

A

neisseria gonorrheae: (lipooligosaccharide, pili, Opa proteins)
borrelia hermsii - relapsing fever

65
Q

What is an IgA protease, which 4 bacteria produce it?

A

Cleaves IgA, which is important for mucosal immunity

neisseria gonorrheae, neisseria meningitidis, haemophilus influenzae, streptococcus pneumoniae

66
Q

Deposition of immune complexes cause tissue damage. What is an immune complex?

A

bacterial antigen, antibody, complement

67
Q

What happens in post-streptococcal acute glomerulonephritis

A

Deposition of immune complexes in glomeruli of kidneys

68
Q

What happens in post-streptococcal rheumatic fever?

A

Autoimmune process with antibodies against streptococcal antigen cross-reacting against host tissue

69
Q

Where is extracellular iron bound in plasma and milk/other secretions?

A

Transferrin

Lactoferrin

70
Q

What is an example of a bacteria that produces siderophores to capture iron?

A

E. coli

71
Q

Bordetella pertussis has higher expression of virulence genes at what temperature?

A

Higher expression at 37 degrees than 20 degrees

72
Q

Yersinia antiphagocytic factors have higher expression in the absence of what

A

Ca2+

73
Q

Corynebacterium diptheriae toxin is more highly expressed in the presence of low what

A

Fe3+

74
Q

What are three main mechanisms of antibiotic resistance?

A

Inhibition of antibiotic
Target site alteration
Decreased intrabacterial accumulation of antibiotic

75
Q

Inhibition of antibiotic occurs by:

Example

A

enzymatic hydrolysis of antibiotic

Ex. enteric gram - bacteria that produce beta lactamases

76
Q

Target site alteration occurs by:

3 examples

A

Decreasing binding affinity for the antibiotic for the target
penicillin resistant streptococcus pneumoniae expressing altered penicillin binding protein (PBP)
methicillin resistant staphylococcus aureus expressing altered PBP
vancomycin resistant enterococcus expressing altered cell wall oligopeptide

77
Q

3 ways in which there could be decreased intrabacterial accumulation of the drug, and one example

A

Decreased membrane permeability
Changes in porin channels
Increased drug efflux often resulting in multidrug resistance
Psuedomonas aeruginosa uses all 3 mechanisms

78
Q

Can plasmids be passed by conjugation

A

Yep

79
Q

One example of virulence genes encoded by a prophage?

A

vibrio cholerae

80
Q

Streptococcus pyogenes containing erythrogenic toxin cause

A

scarlet fever

81
Q

E. coli strains that produce shiga toxin cause what

A

hemorrhagic colitis and hemolytic uremic syndrome

82
Q

What are examples of virulence factors? 5

A 
Toxins
Enzymes
Type III secreted proteins
Adhesins
Siderophores
83
Q

toxins were originally inactivated into toxoids by _________ and _______ but now can be genetically engineered

A

Heat, formaldehyde

84
Q

What is antitoxin?

A

Antisera produced in response to the toxoid (from humans/animals) and can be given as treatment

Microbiology (10 decks)

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