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Microbiology > Microbial Mecanisms Of Pathogenicity > Flashcards

Microbial Mecanisms Of Pathogenicity Flashcards

1
Q

Pathogenicity

A

The ability to cause disease

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2
Q

Virulence

A

The extent of pathogenicity

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3
Q

What factors make a microbe a successful pathogen?

A

if it has the ability to enter and infect a host’s cells, cause damage to the host,
spread from one host to another,
adapt to changing environments and host immune systems,
persist in the environment or host tissues,
and have a broad host range or be specific to a particular host.

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4
Q

Portals of entry:

A

Mucous membranes
Skin
Parenteral route
Preferred portal of entry

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5
Q

Numbers of invading microbes:
ID50:

A

infectious dose for 50% of the test population

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6
Q

Number of invading microbes
LD50:

A

lethal dose (of a toxin) for 50% of the test population

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7
Q

Relative virulence of toxin

A
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8
Q

Adhesins/ligands bind to

A

Receptors on host cells
Glycocalyx: Streptococcus mutans
Fimbriae: Escherichia coli
M protein: Streptococcus pyogenes
Form biofilms

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9
Q

Capsules

A

Prevent phagocytosis
Streptococcus pneumoniae
Haemophilus influenzae
Bacillus anthracis

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10
Q

Cell Wall Components

A

M protein resists phagocytosis
Streptococcus pyogenes
Opa protein inhibits T helper cells Neisseria gonorrhoeae
Mycolic acid (waxy lipid) resists digestion Mycobacterium tuberculosis

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11
Q

Coagulase

A

Coagulates fibrinogen

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12
Q

Kinases

A

Digest fibrin clots

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13
Q

Hyaluronidase

A

Hydrolyzes hyaluronic acid

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14
Q

Collagenase

A

Hydrolyzes collagen

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15
Q

IgA proteases:

A

Destroy IgA antibodies (found in mucous membranes)

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16
Q

Using the Host’s Nutrients: Siderophores

A

Use host’s iron

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17
Q

Direct damage

A

● Disrupt host cell function
● Produce waste products
● Toxins

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18
Q

Toxin

A

substance that contributes to pathogenicity

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19
Q

Toxigenicity

A

ability to produce a toxin

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20
Q

Toxemia

A

presence of toxin in the host’s blood

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21
Q

Toxoid

A

inactivated toxin used in a vaccine

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22
Q

Antitoxin

A

antibodies against a specific toxin

23
Q

Exotoxins

A

Specific for a structure or function in host cell

24
Q

Membrane-disrupting toxins

A

Lyse host’s cells by
Making protein channels in the plasma
membrane
Disrupting phospholipid bilayer

25
Q

Leukocidins

A

Destroys leukocytes

26
Q

Hemolysins

A

Destroys RBCs

27
Q

Streptolysins

A

Destroys immune cells

28
Q

Superantigens are usually an:

A

Exotoxin or other bacterial protein

29
Q

Superantigens cause an:

A

Intense immune response due to release of excessive amounts of cytokines from host cells

30
Q

Cytokines is a general term for:

A

cell communication and immune mediator chemicals (protein)

31
Q

Superantigens symptoms of intense immune response:

A

fever, nausea, vomiting, diarrhea, shock, and death

32
Q

Exotoxin sources

A
33
Q

Exotoxins and lysogenic (virus stays dormant in cells) conversion

A
34
Q

Endotoxins = only one type:

A

Lipid A released from dead Gram negative bacteria Lipopolysaccharide membrane

35
Q

Exotoxins are proteins produced:

A

Inside pathogenic bacteria, most commonly gram-positive bacteria, as part of their growth and metabolism. The exotoxins are then secreted into the surrounding medium during log phase.

36
Q

Exotoxin is a
Ex(s)?

A

toxic substance released outside the cell

Clostridium botulinum, an example of a gram positive bacterium that produces exotoxins

37
Q

Endotoxins are the

A

Lipid portions of lipopolysaccharides (LPS) that are part of the outer membrane of the cell wall of gram-negative bacteria. The endotoxins are liberated when the bacteria die and the cell wall breaks apart.

38
Q

Endotoxins are a
Ex(s)?

A

Toxin composed of lipids that are part of the
outer membrane
Ex: Salmonella typhimurium, an example of a gram-negative bacterium that produces endotoxins

39
Q

Endotoxin and Fever (pyrogenic response)

A macrophage ingests:

A

a gram-negative bacterium.

40
Q

Endotoxin and Fever (pyrogenic response)
The bacterium is digested in a

A

phagosome, releasing endotoxins that induce the macrophage to produce cytokines IL-1 and TNF-

41
Q

Endotoxin and Fever (pyrogenic response)

The cytokines reach the

A

hypothalamus causing it to produce prostaglandins, which reset the body’s “thermostat” to a higher temperature, producing fever.

42
Q

Endotoxin and Fever (pyrogenic response)

As long as cytokines remain in the blood:

A

temperature remains high. When cytokines are gone body temp will go back to normal

43
Q

Endotoxins and the pyrogenic response (4 steps)

A
44
Q

Cytopathic Effects of Viruses

A

● Cell lysis
● Inclusion bodies (what’s left behind)
● Stop macromolecular synthesis in host cell
● Cause cell fusion (syncytium)
● Interfere with cell functions
● Cause antigenic changes on host cell surface leading to cell being destroyed by the immune system
● Chromosomal changes (possibly activation of oncogenes)
● Transformation of host cells- loss of contact inhibition leading to unregulated cell growth

45
Q

Pathogenic Properties of Fungi

A

-Fungal waste products may cause symptoms
-Chronic infections provoke an allergic response
-Trichothecene toxins inhibit protein synthesis :Fusarium
-Proteases:Candida, Trichophyton
-Capsule prevents phagocytosis: Cryptococcus
● Ergot toxin: Claviceps
● Aflatoxin: Aspergillus
● Mycotoxins: Neurotoxins: phalloidin,
amanitin

46
Q

Pathogenic Properties of Protozoa

A

Presence of protozoa
Protozoan waste products may cause symptoms
Avoid host defenses by Growing in phagocytes Antigenic variation

47
Q

Pathogenic Properties of Helminths

A

-Use host tissue
● Presence of parasite interferes with host function
● Parasite’s metabolic waste can cause symptoms

48
Q

Pathogenic Properties of Algae

A

Paralytic shellfish poisoning
-Dinoflagellates
-Saxitoxin
Red tide: more algae than normal (irritating to skin)

49
Q

Pathogenic Properties of Algae

Portals of Exit:

A

-Respiratory tract: Coughing and sneezing
Gastrointestinal tract: Feces and saliva
Genitourinary tract: Urine and secretions
-Skin
-Blood: Arthropods that suck blood; needles or syringes

50
Q

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

A

PORTALS OF ENTRY:

Mucous membranes
• Respiratory tract
• Gastrointestinal tract
• Genitourinary tract
• Conjunctiva
Skin
Parenteral route

51
Q

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

A

PENETRATION OR EVASION OF HOST DEFENSES:
Capsules
Cell wall components
Enzymes
Antigenic variation
Invasins
Intracellular growth

52
Q

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

A

DAMAGE TO HOST CELLS:

Siderophores
Direct damage
Toxins:
• Exotoxins
• Endotoxins
Lysogenic conversion
Cytopathic effects

53
Q

Mechanisms of microbial pathogenicity is fundamental to understanding how pathogens are able to overcome the host’s defenses:

A

PORTALS OF EXIT:

Generally the same as the portals of entry for a given microbe:
• Mucous membranes
• Skin
• Parenteral route

Microbiology (22 decks)

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