Pathogens Host Defenses Flashcards
(103 cards)
1
Q
What are pathogens?
A
Microorganisms capable of causing disease/damage to the host.
2
Q
Do all strains of one species have the same ability to cause disease?
A
No
3
Q
What is a pathogen usually identified by?
A
The set of virulence genes that it carries and expresses
4
Q
What is virulence?
A
A measure of the ability to cause damage to the host
5
Q
What 2 factors is virulence determined by?
A
Invasiveness, toxigenicity
6
Q
What is invasiveness?
A
The ability of microorganisms to become established in the host, or overcome the host defenses and to spread in the tissues
7
Q
What is toxigenicity?
A
the capacity of the microorganism to produce substances known as toxins that damage specific tissues of the host
8
Q
What happens once a host is exposed to a pathogen? 5 steps
A
- Adherence to skin or mucosa
- Invasion through epithelium
- Growth and colonization (production of virulence factors)
- Toxicity or Invasiveness
- Tissue damage, disease
9
Q
What are the 5 different types of virulence factors that pathogens use to invade host tissues?
A
- adhesins
- capsules
- enzymes that destroy host tissues
- Invasins
- Type 3 Secretion Systems (T3SS) and Type 4 Secretion Systems (T4SS)
10
Q
What do adhesins promote?
A
Specific attachment to host cell surfaces
11
Q
How many cell types is one adhesin normally able to attach to?
A
one or many
12
Q
What are Fimbriae/Pili? What do they mediate?
A
Polymers that mediate loose attachment
13
Q
What are Afimbrial adhesins?
A
(not filaments) mediate close attachment
14
Q
In what 2 ways do capsules aid pathogens?
A
- They prevent them from being destroyed by host immune cells (phagocytes)
- They help them attach to host cells and to other bacteria
15
Q
What are 2 essential virulence factors for some bacterial pathogens?
A
Streptococcus pneumonia, Haemophilus influenzae
16
Q
What is epidermis?
A
The outer layer of skin
17
Q
How do most pathogens infect humans?
A
They penetrate the epidermis by using breaches in the skin (wounds, surgery, catheter)
18
Q
What happens when pathogens penetrate the mucosa?
A
They destroy the single-cell layer or invade the cells themselves
19
Q
What is hyaluronidase? Function?
A
An extracellular enzyme that degrades hyaluronic acid
20
Q
Which pathogens release hyaluronidase?
A
Staphylococci, streptococci, clostridia
21
Q
What is hyaluronic acid?
A
A sticky polysaccharide that holds host cells together
22
Q
What is collagen? Function?
A
An extracellular enzyme that degrades the protein collagen present in connective tissues (muscle, cartilage)
23
Q
What is the function of lecithinase? Causes the lysis of what?
A
An extracellular enzyme that degrades lecithin (phosphatidylcholine) in cell membranes – causes the lysis of RBCs and destroys tissue cells
24
Q
What is gas gangrene?
A
The term used to describe the decay or death of an organ or tissue caused by lack of blood supply in wounds infected by anaerobic bacteria
25
What microorganism are present in gas gangrene? What do they do?
Clostridium perfringens. They break down tissue by gas production.
26
What type of microorganism are Clostridium perfringens?
strict anaerobes
27
What enzyme do Clostridium perfringens use to lyse host cells in gas gangrenes? What enzymes do they use to destroy the extracellular matrix?
Lecithinase
28
What are hemolysins? What are the different types of hemolysins?
A substance in the blood that destroys RBCs and liberates hemoglobin.
Enzymes, cytolysins
29
What are two examples of hemolysin enzymes?
Lecithinase, phospholipase
30
What is a characteristic of hemolysin cytolysins?
Pore-forming
31
What does the release of the extracellular enzyme leucocidin target & cause the lysis of?
Leucocytes (white blood cells) produced by staphylococci, streptococci, and some gram neg bacteria
32
What are leucocytes?
White blood cells
33
What do the extracellular proteins, Proteases, do once they are released?
The degrade complement proteins and/or antibodies
34
What produces the extracellular enzyme coagulase?
virulent staphylococci
35
What do coagulase enzymes cause? What does this do?
insoluble fibrin to be deposited on bacterial cells. This blocks the bacteria from the immune system
36
What are invasins?
Surface proteins, or injected proteins, that allow microorganisms to enter cells (invade host cells)
37
What is one major virulence factor of intracellular pathogens?
Invasins
38
How does the invasion of host cells benefit bacterial pathogens?
It protects them against the host immune system and is a good source of nutrients
39
What are 4 examples of pathogens that have invasins?
Mycobacterium, Salmonella, Listeria, Chlamydia
40
In what 4 ways do pathogens modify the properties and behaviors of host cells in order for them to grow inside of host cells?
1. block phagosome maturation (block digestion)
2. Increase size of vacuole
3. Acquire nutrients
4. Block detection of intracellular infection and response (host defense)
41
What is a phagosome?
a vacuole in the cytoplasm of a cell, containing a phagocytosed particle enclosed within a part of the cell membrane.
42
What two type of secretion systems do a lot of gram-negative pathogens use?
Type 3 (T3SS) and Type 4 (T4SS)
43
What does a T3SS do?
It forms a channel through the bacterial cytoplasmic membrean + periplasm + outer membrane + host cell membrane so bacterial proteins can be injected into the host cell cytosol
44
What are the 3 functions of T3SS?
1. Invasion of host cells
2. Block phagosome maturation
3. Take control of host cells
45
How is T4SS different from T3SS?
T4SS does not have a needle-like structure
46
What are T3SS and T4SS's also called?
injectisomes
47
What are toxins?
Extracellular enzymes that cause damage
48
Is toxin production always necessary for an organism to be highly virulent? What else can be the cause of damage to an organism?
No. Damage can be caused by the host's own immune system or be a result of the large # or pathogens present
49
What are the 2 categories of diseases that bacterial pathogens are associated with?
1. Infectious diseases
| 2. Intoxications
50
What do infectious disease result from?
The pathogen's growth
51
What do intoxication's result from?
The presence of a specific toxin
52
What are 3 examples of infectious diseases?
Pneumonia
Meningitis
Syphilis
53
What is an examples of an intoxication?
food poisoning
54
What 2 categories are toxins divided into?
Exotoxins & endotoxins
55
What is an exotoxin?
A toxin secreted into the surroundings as the bacterial pathogen grows
56
What is an endotoxin?
A toxin that is part of the bacterial pathogen
57
Are exotoxins soluble or insoluble?
soluble
58
When are exotoxins secteted/released?
When the organism is lysed
59
What macromolecule are exotoxins normally?
Proteins
60
What destroys exotoxins?
Heat (heat-liable)
61
What inactivates exotoxins? Exotoxins are highly what?
Antibody response inactivates exotoxins. They are highly immunogenic (produce an immune response)
62
What are exotoxins categorized by? Give 5 examples.
Their target.
1. Neurotoxins (nerve tissue)
2. Enterotoxins (GI tract)
3. Nephrotoxins (kidney)
4. Hepatotoxins (liver)
5. Cardiotoxins (heart)
63
What are 2 examples of extracellular exotoxins?
Hyaluronidase, collagenase
64
What type of toxin are AB toxins?
Exotoxins
65
What do AB toxins do? What 2 subunits are they made up of?
They modify host cells. Enzymatic subunit A + binding/cell entry B
66
What does Subunit A of AB toxins do?
It modifies a target inside the host cell, leading to damage to the host.
67
What is an example of an enzymatic subunit A of an AB toxin?
ADP-ribosyltransferase
68
What does Subunit B of AB toxins do? What does this provide?
It binds to specific cell receptors providing tissue/cell type specificity
69
What is an example of an AB toxin? What category of an AB toxin does it fall under?
Clostridium botulinum, a neurotoxin
70
What does the Botulinum neurotoxin block? What is the effect?
Blocks acetylcholine release in neuromuscular junction, leading to Flaccid paralysis (this inhibits muscle contractions)
71
What organisms does the AB neurotoxin Botulunim affect?
Humans
Cattle
Horses
Ducks
72
In what silly way do humans use the Botulinum toxin?
BOTOX!
73
What does BOTOX do?
- Reduces wrinkles / frown
- Controls muscle spasms
- treats for hyperhydrolysis (excessive sweating)
74
What does the acetylcholine neurotransmitter normally do? How does the botulism toxin affect this?
It induces contraction of muscle fibers.
Botulism toxin blocks the release of A, inhibiting contraction
75
What is an example of an AB5 toxin?
Cholera toxin (Vibrio cholerae)
76
What is an infection by the cholera toxin Vibrio cholerae characterized by?
Severe diarrhea
| Massive loss of fluid from the GI tract
77
In the cholera toxin (Vibrio cholerae), what is the function of the A subunit? B subunit?
A: Adenylate cyclase, produces cAMP
B: binds to intestinal cells
78
When is lipid A of LPS from gram-neg bacterial pathogens released?
During multiplication of lysis of bacterial cells
79
Can endotoxins be inactivated? Why?
No, heat stable
80
Are endotoxins strongly or weekly immunogenic? How?
Weakly - no antibody are produced agains LPS
81
Endotoxins are very effective activators of what? What do they produce?
The immune system. They produce general systemic effects such as pyrogenic (heat) fever, shock, weakness, inflammation, diarrhea, septic shock
82
Endotoxins are an important cause of symptoms in what type of bacterial infections? What are 2 exmples?
In all gram-neg
Salmonella, E.coli
83
Exotoxins stimulate the host defense system to produce what? This makes them highly what?
Antibodies that can neutralize the toxin.
Highly antigenic
84
When you get a vaccine, what is actually injected into your body?
Toxoids
85
Can exotoxins or endotoxins become toxoids?
Exotoxins only
86
What are toxoids?
ENXOtoxins inactivated by heat or formaldehyde
87
What characteristic of exotoxins do toxoids still possess?
Toxoids are no longer toxic, but are still antigenic (induce antibody response)
88
Why can endotoxins not be converted into toxoids?
They cannot be inactivated by heat or formaldehyde
89
Are there any vaccines against endotoxins?
No, because can not be transformed into toxoids
90
What are the chemical properties of exotoxins?
Proteins excreted by certain gram-positive or gram-negative bacteria; generally heat-liable
91
What are the chemical properties of endotoxins?
Lipopolysaccharide-lipoprotein complexes, released on cell lysis as part of the outer membrane of gram-negative bacteria; extremely heat-stable
92
What is the mode of action/symptoms of exotoxins?
Specific; usually binds to specific cell receptors or structures; either cytoyoxin, enterotoxin or neurotoxin with defined, specific action on cells or tissues
93
What is the mode of action/symptoms of endotoxins?
General; fever, diarrhea, vomiting
94
What is the toxicity of exotoxins?
Often highly toxic, sometimes fetal
95
What is the toxicity of endotoxins?
Weakly toxic, rarely fatal
96
What is the immunogenicity response of exotoxins?
Highyl immunogenic; stimulate the production of neutralizing antibody (antitoxin)
97
What is the immunogenicity response of endotoxins?
Relatively poor immunogen; immune response not sufficient to neutralize toxin
98
What is the toxoid potential of exotoxins?
Treatment of toxin with formaldehyde will destroy toxicity, but treated toxin (toxoid) remains immunogenic
99
What is the toxoid potential of endotoxins?
None
100
What is the fever potential of exotoxins?
Does not produce fever in host
101
What is the fever potential of endotoxins?
Pyrogenic (heat), often induces fever in host
102
What are pathogenicity islands?
the section of the chromosome encoding virulence factors
103
Slide 26
Host defenses
