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Veterinary Bacteriology and Mycology > Bacterial Pathogenesis > Flashcards

Bacterial Pathogenesis Flashcards

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1
Q

Compared to bacterial population in nature, how many bacteria cause animal diseases?

A

Only relatively few bacteria cause animal diseases.

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2
Q

What is the complex relationship between animals and their natural bacteria?

A

It is a mutually beneficial symbiotic relationship critical to the animals’ health.

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3
Q

What is microbiota?

A

Microorganisms that naturally inhabit a region of the body.

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4
Q

What is an opportunistic pathogen?

A

Natural microbiota causing opportunistic infections when they enter parts not their normal site on the host or during host immunosuppression.

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5
Q

What are true pathogens?

A

Non-natural microbiota that enter the body and cause disease.

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6
Q

What is pathogenicity?

A

The ability of a pathogen to inflict damage on its host.

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7
Q

What is virulence?

A

The degree of pathogenicity within a group or species as determined by the virulence factors.

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8
Q

What are virulence factors?

A

Molecules expressed or secreted by bacteria that enable colonization, evasion of the immune response, entry into or out of host cells, and/or obtaining nutrition from the host.

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9
Q

What is an infection?

A

When an organism has established itself in a host, whether causing damage or not.

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10
Q

What is disease?

A

Impairment to the host function as a result of injury or damage.

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11
Q

What is etiology?

A

Causes of disease due to damage or pathology; infectious disease etiology is the microbe causing the disease.

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12
Q

What are the 3 types of infectious disease?

A
  1. Nosocomial 2. Iatrogenic 3. Zoonotic
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13
Q

Give examples of symptoms vs signs.

A

Symptoms: pain, nausea, appetite, etc. (felt by the host). Signs: body temperature, rash, swelling, stool consistency, etc. (able to be observed).

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14
Q

What are the steps in order of the development of disease?

A
  1. The exposure or contact 2. Incubation period 3. Prodromal period 4. Period of illness 5. Period of decline 6. Period of convalescence.
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15
Q

What is the first step in how a pathogen causes a disease?

A

Adhesion: microbes attach to the host at a portal of entry using special surface molecules called adhesins.

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16
Q

What are the 3 different portals of entry for a microbe into the body?

A
  1. Mucous membranes 2. Skin 3. Parenteral route.
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17
Q

What are the different mucous membrane portals of entry for a microbe?

A

Respiratory, GIT, urogenital, or conjunctival.

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18
Q

What are the different skin portals of entry for a microbe?

A

Natural openings (hair follicles, sebaceous glands), penetration of the skin, or infection of the skin itself.

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19
Q

What is the parenteral portal of entry for microbes?

A

Through a breach in the skin and mucous membrane.

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20
Q

True or false: pathogens have no preference in their portal of entry into the host.

A

False: pathogens may have preferred portals of entry to cause disease; through other portals they may be unable to cause disease.

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21
Q

Give some examples of situations of entrance of a pathogen into its host.

A
  1. Inhalation 2. Ingestion of contaminated food or pasture 3. In utero transmission to developing fetus 4. Lesions to skin or mucous membranes.
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22
Q

Give some examples of situations of exit of a pathogen from its host.

A
  1. Nasal secretions 2. Saliva 3. Secretion in milk or colostrum 4. Excretion via feces and urine 5. Contamination of environment with placenta and other gestational tissues or fluids at birth.
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23
Q

What is pathogenesis?

A

A series of events from initiation to the development of a disease.

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24
Q

Pathogenesis begins with what?

A

Contact or exposure to a pathogen.

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25
What tends to dislodge bacteria from the body during pathogen adhesion?
Innate immunity and physical and mechanical barriers.
26
What are examples of bacterial adhesins that attach to the surface receptors of portal cells during adhesion?
Pili, flagella, glycocalyx, capsule, etc.
27
What are biofilms?
Formations of microbial communities that share nutrients and are shielded by extracellular polymeric substance that resists phagocytosis.
28
What are the 3 steps of pathogenesis?
1. Contact/exposure 2. Adhesion 3. Resistance to innate immunity.
29
What allows for resistance to innate immunity of a pathogen?
Possession of a capsule for anti-phagocytic properties and cell wall components such as M proteins of streptococci or mycolic acid of M. tuberculosis.
30
What are 4 different adhesion strategies of bacteria and an example of each?
1. Bind to mucus (commensal bacteria) 2. Bind surface lectins (many fimbriae) 3. Bind surface protein (invasion protein of Y. enterocolitica binding B-integrins) 4. Bind extracellular matrix protein (many gram + bacteria).
31
For most pathogens to be successful they must be able to what?
Adhere avidly to host cells and tissues, especially at mucosal surfaces.
32
What are the different methods of resistance and overcoming the initial immune responses by bacteria?
1. Production of certain enzymes 2. Antigenic variations.
33
What are different enzymes that serve to assist pathogens in resistance to initial immune responses?
1. Coagulase 2. Kinases 3. Hyaluronidase 4. Collagenase 5. IgA proteases.
34
What does coagulase do?
Clots fibrin around S. aureus and protects against immune cells.
35
What do kinases do?
Digest clots and allow the spread of bacteria.
36
What does hyaluronidase do?
Digests the polysaccharide holding cells together.
37
What does collagenase do?
Breaks down collagen that holds the skin to deeper tissues, enabling the bacteria to spread.
38
What do IgA proteases do?
Cleaving IgA, making it no longer protective.
39
What is antigenic variation?
Change in shape of surface antigens of pathogens that renders antibodies ineffective.
40
Once inside a tissue, what are the two locations of bacteria to cause damage?
1. Extracellular: adhere to and multiply on the surfaces of cells (interstitial spaces, blood, lymph, or epithelial surfaces). 2. Intracellular: enter and proliferate inside the cell (cytoplasmic or vesicular).
41
What is the life cycle of an extracellular pathogen?
Entry -> attachment -> resist phagocytosis -> resist action of complement -> acquire nutrients.
42
What is the life cycle of an intracellular pathogen?
Entry -> attachment -> invasion -> resist intracellular destruction -> acquire nutrients.
43
For intracellular bacteria to enter into host non-phagocytic cells, they make use of what?
Invasins.
44
What are invasins?
Surface proteins produced by bacteria that rearrange the filaments of actin filaments causing membrane ruffling and phagocytosis.
45
What are the 4 methods of action of invasins to allow for intracellular bacteria to enter into the host?
1. Bind to receptors on host cell surfaces (Yersinia) 2. Be injected into host cell (Type III secretion by Salmonella) 3. Actin fibers can be utilized intracellularly to move through host cells (transcytosis) (Listeria monocytogenes) 4. May be used by professional phagocytes to bypass normal phagosome.
46
Survival of a pathogen inside of a cell is achieved by what?
Avoiding lysosomes fusion with phagosomes.
47
What are spreading factors?
A family of bacterial enzymes that affect the physical properties of tissue matrices and intercellular spaces, promoting the spread of the pathogen through different host tissues.
48
What are examples of spreading factors?
1. Hyaluronidase 2. Collagenase 3. Neuraminidase 4. Streptokinase and staphylokinase 5. Edema factor.
49
What is the role of hyaluronidase as a spreading factor and what is it produced by?
Depolymerizes hyaluronic acid, the interstitial cement substance of connective tissue. Produced by streptococci, staphylococci, and clostridia.
50
What is the role of collagenase as a spreading factor and what is it produced by?
Breaks down collagen. Produced by Clostridium histolyticum and Clostridium perfringens.
51
What is the role of neuraminidase as a spreading factor and what is it produced by?
Degrades neuraminic acid (sialic acid) present on epithelial cells of the mucosa. Produced by Vibrio cholerae, Shigella dysenteriae, P. multocida, and M. haemolytica.
52
What is the role of streptokinase and staphylokinase as spreading factors?
Convert inactive plasminogen to plasmin which digests fibrin.
53
What is the role of edema factor of B. anthracis as a spreading factor?
Adenylate cyclase activity promotes bacterial invasion.
54
What are the characteristics of endotoxins?
1. Integral part of cell wall 2. It is an LPS; lipid A is toxic 3. Heat stable 4. Antigenic with questionable immunogenicity 5. Toxoids not produced 6. Many effects on host 7. Produced only by gram - bacteria.
55
What are the characteristics of exotoxins?
1. Released from the cell before or after lysis 2. It is a protein 3. Heat liable 4. Antigenic and immunogenic 5. Toxoids can be produced 6. Specific effect on host 7. Produced by gram + and gram - bacteria.
56
What are the general stages of pathogenesis?
1. Exposure 2. Adhesion 3. Invasion 4. Infection colonization, toxin release, and tissue damage/disease 5. Transmission via coughing, sneezing, body secretions, and excretions.
57
What are the methods of damaging the host by a pathogen?
1. Use of host nutrients 2. Direct damage 3. Toxins.
58
Give an example of how a pathogen uses host nutrients to cause damage.
Iron is needed by most pathogenic bacteria, and they use siderophores to deny host cells of necessary iron.
59
What are examples of pathogens causing direct damage to the host?
1. Disruption of host cell function 2. Uses host cell nutrients 3. Produces waste products 4. Multiplies in host cells causing rupture 5. Most host cell damage caused by toxins.
60
What are toxins?
Poisonous substances produced by bacteria.
61
What are the 3 types of exotoxins?
1. Cytotoxins: kill cells (e.g., diphtheria toxin) 2. Neurotoxins: interfere with normal nerve impulses (e.g., botulinum toxin) 3. Enterotoxins: affect cells lining the GIT (e.g., cholera toxin/choleragen).
62
What is the limulus test?
Can be used to determine rapidly and specifically the cumulative content of gram-neg bacteria in foods using Limulus Amebocyte Lysate.
63
What are the characteristics of pathogenic bacteria?
1. Transmissibility 2. Adherence to host cells 3. Invasion of host cells and tissue 4. Evasion of the host immune system 5. Toxigenicity.
64
A bacterium may cause disease in what 3 ways?
1. Destroying tissue (invasiveness) 2. Producing toxins (toxigenicity) 3. Stimulating overwhelming host immune responses.

Veterinary Bacteriology and Mycology (8 decks)

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