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DWT > Bacteriology 2: Host-Environment-Pathogen > Flashcards

Bacteriology 2: Host-Environment-Pathogen Flashcards

1
Q

What is a host?

A

Any organism that support the survival and growth of microorganisms (parasites, viruses, bacteria)

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2
Q

What is a Saprocyte?

A

Organism that live on dead or decaying organic matter (environment).

**Usually not parasite but can occasionally live in/on animals causing disease

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3
Q

What is a parasite? does it cause harm?

A

Organism that lives on/within another living organism and derives nutrients from host
- May or may not cause harm. Must be under the right circumstances

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4
Q

Saphrocyte vs parasite

A
  • Incomplete distinction
  • Some organisms may live as one for the other
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5
Q

Define commensal

A

Organism that lives in/on host without causing disease
- Normal Flora

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6
Q

What is a pathogen?

A

Parasitic and saprophytic bacteria which have the potential to cause disease.
- Normal Flora
- Don’t always cause disease but can under the appropriate conditions

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7
Q

Carriers (Carrier state)

A

Animals with specific bacterial pathogens present in only part of the population
- May be causing subclinical disease or no disease BUT still shed

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8
Q

Pathogens VS Carrier state

A
  1. A pathogen on most animal = Normal Flora -Can’t eliminate
  2. A pathogen on few animals = Carrier animals -Can eliminate
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9
Q

Disease from Normal Flora?

A

Opportunistic

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10
Q

Characteristics of carrier animal diseases?

A
  • Contagious
  • CAN be eliminated if carriers are identified and culled/cured
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11
Q

Where in your body is the normal flora?

A

Skin- Everywhere, higher is folds, gramPOS dominate (i.e armpits)
Ear- Ear flap (pinna), vertical canal (fewer), horizontal canal (Fewer), gramPOS dominate
Udder- Around the streak canal (Fewer as advancing into udder)
Eye- Conjunctiva (Low number of bacteria, Cornea (VERY few), gramPOS dominate
Respiratory tract- Cranial to larynx, Some gramNEG
Reproductive tract- Distal to the cervix, Mixture of gramPOS and gramNEG
Urinary Tract- Urethra (Moving toward bladder = fewer and fewer bacteria), Mixture of gramPOS and gramNEG

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12
Q

Sterile sites

A

Post Tympanic membrane
teat cistern
Past cornea (inside eye)
Below the larynx sterile
Bladder
Uterus - past the cervix = sterile

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13
Q

How does sterile site respond infection?

A

Cleared rapidly by host defense
Do not induce imflammation

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14
Q

What is the significance of a sterile site?

A

-Influences form of sample collection
- Influences interpretation of bacteria

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15
Q

What is a disease

A

Any abnormal condition affecting an animal

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16
Q

What is an endogenous infection?

A

An infection arising from bacteria that live on the skin, mucus membrane as commensals

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17
Q

What is and Exogenous infection?

A

An infection from environmental bacteria. Occurs when impaired host defenses allow these bacteria to invade

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18
Q

What is a pathogen

A

Those bacteria capable of causing disease

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19
Q

What is pathogenicity?

A

The capacity of a bacteria to produce disease in a host

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20
Q

What is virulence?

A

The strength of pathogenicity

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21
Q

What is an obligate pathogen

A

Bacteria that must cause disease in order to be transmitted from one host to another

*Relatively less common

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22
Q

What is an opportunistic pathogen?

A

Bacteria that are normal flora or saphrocytes. Cause disease when the host is compromised

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23
Q

Factors that may allow opportunistic pathogens?

A
  • Damage to tissues
    -Introduction of microorganisms
    -Disturbance of normal flora
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24
Q

What is infectivity?

A

Capacity of an organism to become established in a host.

Involves: Ability to penetrate tissues, survive host’s defenses, and multiply/disseminate within the host

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25
Q

How does the number of a potentially pathogenic bacteria present offbeat the development of a disease?

A

In general: the more bacteria present: the more likely a disease will occur

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26
Q

What is host tissue compromise usually due to?

A
  • Damage of host tissues
  • Impairment of innate immunity host defenses
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27
Q

What does it mean to be immune compromised?

A

Impairment of the ADAPTIVE immune system

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28
Q

Does compromise mean the same thing as immunocompromise ?

A

No

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29
Q

_____ amount of highly virulent bacteria will lead to disease

A

Small

30
Q

______ amount of weakly virulent pathogen will cause disease

A

Large

31
Q

E. Coli, Streptococci are highly virulent bacteria meanly they will be _____ isolated from infections

A

Commonly

32
Q

Weakly virulent pathogens with be _____ isolate from infections

A

Rarely

33
Q

What is the first line of defense?

A

Innate immunity

34
Q

What is the second line of defense?

A

Adaptive immunity

35
Q

Innate vs adaptive immunity
- Self-recognition
- Lag phase
- diversity
- Memory

A

See photo

36
Q

Where is the innate immune system?

A

Skin/Mucus membranes

37
Q

What type of cells does innate immunity use?

A

Phagocytes: macrophages, neutrophils

38
Q

Can activating of the innate immune system cause damage?

A

Yes, leads to fever causing damage to host

39
Q

What are the two divisions of the adaptive immune system?

A
  1. Antibody mediated immunity: Opsonization, neutralization, Lysis of bacteria
  2. Cellular mediated immunity: destruction of intracellular bacteria by cytotoxic t cells
40
Q

What is another term for a predisposing factor leading to infection?

A

Stressor

41
Q

What are examples of innate stressors?

A

Species, Sex, Age. (Aka. Key questions in outbreak investigation)

42
Q

What are some external stressors?

A

Extreme temperatures, Nutritional deficiencies, overcrowding, transportation, change in feed, weaning

43
Q

What are some internal host stressors?

A
  • Tissue damage: trauma, other infections, allergies
  • Host response: endocrine changes, immunosuppressive organism (viruses) or drugs
44
Q

Why is it important to identify the stressor or predisposing factor?

A

To properly treat and CONTROL these disease. It will reappear if you don’t fix the cause

45
Q

Host + host compromise+ bacteria +

A

Infection

46
Q

What is a “good” pathogen infection?

A

Highly virulent + little host compromise

AKA
-Ability to attach and colonize
-Ability to gain access to the body (Invade)
-Ability to evade the innate immunity
-Ability to produce molecules that cause dysfunction or damage

47
Q

How do you target a disease caused by a weakly virulent pathogen?

A

Aim to increase the host defense mechanisms

48
Q

How do you treat a highly virulent pathogen?

A

Aim to attack the bacteria. Increasing host defense mechanisms won’t do much.

49
Q

List 6 sources of bacteria

A
  1. Normal flora
  2. Animals incubating disease
  3. Animals with overt disease
    4.Carrier animals with sub clinic or no clinical signs
  4. Fomites
  5. Environment (Ex: saprocytes)
50
Q

What is a host defense mechanism?

A

Stops the infection from developing AKA immune system (innate and adaptive)

51
Q

Six routes of bacterial infection transmission

A

1.Inhalation
2.ingestion
3.Inoculation
4.Transplacental
5.Genital Tract
6.umbilicus

52
Q

What is genetic variation of bacteria?

A

Coding for virulence factors.
- Phase variation
- May have random phase variation
- Genetic elements (Aka plasmids and phases)
- Being clonal or non-clonal

53
Q

What is phase variation?

A

Virulence factors are not always expressed but turned on when needed

CAN also be random phase variation where this occurs randomly

54
Q

Virulence factors for adhesions

A
  • Fimbriae (pili): Present on some bacteria (Specifically gramNEG) and assist with adhesions through SPECIFIC interaction with cell surface receptors
  • Adhesions: Weaker adhesions by physics-chemical attractions allow the bacteria to attach and colonized body sites
55
Q

Virulence factors for Invasion

A
  • Bacteria can ACTIVELY or PASSIVELY enter host
    — Active entry via epithelium using specific molecules including exotoxins
  • Bacteria enter through compromised tissues
56
Q

What is an exotoxin?

A

A toxin released by bacteria into its surroundings

57
Q

Anti-phagocytic molecules

A

-Anti-phagocytic molecules (Evasion)
— Capsule, slime layer, biofilms
— Protect bacterial from ingestion and killing by phagocytic cells

58
Q

What is the main strategy a body uses to overcome anti-phagocytic molecules?

A

Development of specific antibody and opsonization allowing phagocytosis

59
Q

What is iron sequestration and when is it necessary?

A

Bacteria using siderophores that remove iron bound to lactoferrin/transferrin molecules or to RBC
—NEEDS iron to survive in the body

60
Q

What does bacteria NEED to survive in the body?

A

Iron

61
Q

Survival in protected sites
Extra cellular

A

Usually cleared by development of an antibody

62
Q

Survival in protected sites- intracellular

A

Must be facultative intracellular parasite, obligate intracellular parasite

63
Q

What does surviving within a cell allow the bacteria to evade?

A

Phagocytosis
Immune system (antibodies)
Antibiotics that act extracellular

64
Q

Facultative intracellular parasites

A

Can live in or out of the cell
Some major pathogens: salmonella, brucella

65
Q

Obligate intracellular parasites

A

MUST live within cells while in the host
- Less common

66
Q

If you see a bacteria intracellular on a slide what does that mean?

A

It was:
A Facultative intracellular bacteria
A obligate intracellular bacteria
A phagocytosed bacteria

67
Q

What is a toxin?

A

Virulence factor used for destruction of tissue
- Directly: on cell
-Indirectly: through lysis of phagocytes
- Specific dysfunction: without causing da,age to cell
- Inflammatory cascade: fever

68
Q

What are the two categories of toxins

A

Endotoxins
Exotoxins

69
Q

Endotoxin vs exotoxin

A

See photo

70
Q

Factors that allow for survival in tissues

A

-Anti-phagocytic molecules
-Iron sequestration
-intracellular survival

DWT (28 decks)

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