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CMOD- Block1 > Micro: Pathogenesis, Part 1 > Flashcards

Micro: Pathogenesis, Part 1 Flashcards

1
Q

A microorganism is a pathogen if it is capable of what?

A

causing disease

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2
Q

What are opportunistic pathogens?

A

those that rarely if ever cause disease in immunocompetent people, but can cause serious infection in immunocompromised people

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3
Q

Virulence is a ___ measure of ____.

A

quantitative measure of pathogenicity

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4
Q

How is virulence measured? (like, what is the base unit)

A

by the number of organisms required to cause disease

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5
Q

What is LD50?

A

the number of organisms needed to kill half the hosts

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6
Q

What is ID50?

A

the LD50 is the number of organisms needed to cause infection in half the hosts

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7
Q

Organisms with lower LD50 are said to be more or less virulent than those with higher LD50?

A

more virulent, because fewer are needed to kill half the hosts

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8
Q

THe infectious dose of bacteria depends primarily on their ___ ___.

A

virulence factors

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9
Q

Why is there is a parasitic relationship of bacteria to host cells?

A

because the presence of bacteria is detrimental to the host cells

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10
Q

What is an obligate intracellular parasite?

A

bacterial pathogens that can only grow within cells; for example Chlamydia and Rickettsia

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11
Q

What is a facultative parasite?

A

bacteria that can grow within cells, outside cells, or on bacteriologic media

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12
Q

People get infectious disease when microorganisms do what to host defenses?

A

overpower host defenses

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13
Q

What are the two critical determinant in overpowering the host?

A
  1. number of organisms to which the host or person is exposed
  2. the virulence of these organisms
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14
Q

What are some important causes of reduction in our host defenses?

A

genetic immunodeficiences, such as agammagolbulinemia; acquired immunodeficiencies, such as AIDS; drug-induced immunosuppression, such as in patients with organ transplants; and cancer patients receiving chemotherapy

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15
Q

What is an asymptomatic infection?

A

when a person has acquired an organism, but no infectious disease occurs because host defenses were successful; these are recognized by detection of antibody against the organism in the patient’s serum

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16
Q

Bacteria cause disease by two major mechanisms. What are they?

A
  1. toxin production

2. invasion and inflammation

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17
Q

Toxins fall into two categories. What are they? Describe them.

A
  1. exotoxins = polypeptides released from the cell

2. endotoxins = lipopolysaccharides, which form integral part of cell wall

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18
Q

Endotoxins occur only in Gram-____ rods and cocci, and cause ____, ___, and other generalized symptoms.

A

Gram-negative; fever, shock

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19
Q

Can endotoxins and exotoxins cause symptoms by themselves, or must the bacteria also be present in the host?

A

endotoxins and exotoxins CAN cause symptoms by themselves; the presence of the bacteria in the host is NOT required

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20
Q

What is a communicable infection?

A

one whose bacteria are spread from host to host

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21
Q

What term is applied to highly communicable infections?

A

contagious

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22
Q

What makes an infection an epidemic, and what makes it a pandemic?

A

epidemic is it occurs more frequently than usual; pandemic if it has a worldwide distribution

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23
Q

What type of infection is constantly present at a low level in a specific population?

A

endemic

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24
Q

Some infection result in a latent state, which ends when what happens?

A

after the latent state, there can be reactivation of the growth of an organism and recurrence of symptoms

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25
Q

Typhoid Mary is an important source of infection and public health hazard. Why does everyone hate Typhoid Mary?

A

Because she is a chronic carrier. Bitch.

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26
Q

What is a chronic carrier state?

A

a state in which the organisms continue to grow with or without producing symptoms in the host

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27
Q

What is the significance of colonization in determining the pathogenic source of an infection?

A

colonization refers to the presence of a new organism that is neither a member of the normal flora, nor the cause of the infectious symptoms

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28
Q

What are the 7 generalized stages of infection?

A
  1. transmission
  2. evasion of host defenses
  3. adherence - usually by pili
  4. colonization
  5. symptoms - caused by toxin/inflammation
  6. host response
  7. progression/resolution
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29
Q

Interrupting the chain of transmission is an excellent way to ___ the spread of infectious disease.

A

prevent

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30
Q

What is a fomite?

A

an inanimate object that serves as a source of microorganisms that can cause infectious disease; ex: towel

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31
Q

What are the modes of human-to-human transmission of bacteria?

A
  • direct contact (sexual, birth canal)
  • no direct contact (ex: feces into soil/water, then into food)
  • transplacental (just what it says: mother to baby)
  • bloodborne (transfusion, IV drugs)
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32
Q

What are non-human sources of human infectious agents?

A
  • soil source
  • water source
  • animal source (directly, insect vector, animal excreta)
  • fomite source
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33
Q

Pathogens exit the infected patient most frequently from what two tracts?

A

respiratory and GI

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34
Q

What are the 5 diseases transmitted by ticks in the US, and which is the most common?

A
  1. Lyme disease - most common
  2. Rocky Mountain spotted fever (Rickettsia)
  3. ehrlichiosis
  4. relapsing fever
  5. tularemia
35
Q

The process of vertical transmission involved transmitting viruses, bacteria, and other microbes from ___ to ___.

A

mother to offspring

36
Q

What are the 3 modes by which microorganisms can be vertically transmitted?

A
  1. placenta
  2. birth canal
  3. breast milk
37
Q

The process of horizontal transmission involved transmitting viruses, bacteria, and other microbes from ___ to ___.

A

person to person

*that is not mother to offspring

38
Q

What are the 4 important portals of entry for pathogens?

A
  1. respiratory tract
  2. GI tract
  3. genital tract
  4. skin
39
Q

What 3 types of bacteria can cause diarrheal diseases?

A
  1. Gram+ cocci
  2. Gram+ rods
  3. Gram- rods
40
Q

What 3 types of bacteria can cause non-diarrheal diseases?

A
  1. Gram+ rods
  2. Gram- rods
  3. mycobacteria
41
Q

Animals can either be the ___ (reservoir) or ___ (vector) of transmission of pathogens to humans.

A

source; mode

42
Q

Diseases for which animals are reservoirs are called ____.

A

zoonoses

43
Q

What are adherence mechanisms bacteria may have for enhancing their ability to cause disease?

A

specialized structures, such as pili, or the ability to produce substances, such as capsules or glycocalyces, that allow them to adhere to surfaces of human cells

44
Q

What are adhesins?

A

molecules that mediate the adherence of bacteria to cell surfaces

45
Q

What is a biofilm and what does it do?

A

a protective matrix formed by bacteria after they attach to a host; consists of various polysaccharides and proteins; it protects bacteria from both abx and host cell defenses, and retards wound healing

46
Q

Biofilms form especially on ___ bodies, but can also form on ___ structures.

A

foreign; native

47
Q

In the process of quorum sensing, bacteria grow in a nonaggressive manner until a quorum is sensed. at which point, what happens?

A

at which point he bacteria realize they are numerous enough and start synthesizing new bacterial virulence factors that contribute to pathogenesis, such as biofilms

48
Q

Why do phagocytes adhere poorly to foreign bodies? (such as artificial heart valves and joints)

A

these surfaces lack selectins and other binding proteins that the phagocytes need

49
Q

What are curli?

A

surface proteins found on some strains of E. coli and Salmonella that mediate binding of the bacteria to endothelium and EC proteins such as fibronectin and serum proteins such as Factor XII

50
Q

What are the 4 most prominent pathogenetic enzymes secreted by bacteria?

A
  1. collagenase and hyaluronidase
  2. coagulase
  3. IgA protease
  4. leukocidins
51
Q

Collagenase and hyaluronidase degrade their namesake molecules, allowing what to happen?

A

bacteria to spread through subQ tissue; important in cellulitis caused by Strep. pyogenes

52
Q

What does coagulase do?

A

accelerates the formation of a fibrin clot from fibrinogen; this may protect the bacteria from phagocytosis

53
Q

What does IgA protease do? (immunoglobulin A protease)

A

degrades IgA, allowing the bacteria to adhere to mucous membranes

54
Q

What do leukocidins do?

A

destroy neutrophilic leukocytes and macrophages

55
Q

Name 2 groups of antiphagocytic factors.

A
  1. capsule: prevents phagocytes from binding, but is defeated by opsonization
  2. cell wall proteins of Gram- cocci: protein M (antiphagocytic) and protein A (binds IgG, prevents complement activation)
56
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Streptococcus pneumoniae

A
  • Gram+ cocci
  • polysaccharide capsule
  • vaccine Yes
57
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Streptococcus pyogenes

A
  • Gram+ cocci
  • M protein
  • vaccine No
58
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Staphylococcus aureus

A
  • Gram+ cocci
  • Protein A
  • vaccine No
59
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Neisseria meningitides

A
  • Gram- cocci
  • Polysaccharide capsule
  • vaccine Yes
60
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Bacillus anthracis

A
  • Gram+ rods
  • polypeptide capsule
  • vaccine No
61
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Haemophilus influenzae

A
  • Gram- rods
  • polysaccharide capsule
  • vaccine Yes
62
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Klebsiella pneumoniae

A
  • Gram- rods
  • polysaccharide capsule
  • vaccine No
63
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Escherichia coli

A
  • Gram- rods
  • protein pili
  • vaccine No
64
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Salmonella typhi

A
  • Gram- rods
  • polysaccharide capsule
  • vaccine No
65
Q

For the following bacterium, name the Gram category, virulence factor, and if it’s used in vaccine:
Yersinia pestis

A
  • Gram- rods
  • V and W proteins
  • vaccine No
66
Q

Bacteria can produce two types of inflammation. NAME THEM.

A
  1. pyogenic

2. granulomatous

67
Q

What does pyogenic inflammation mean, and what are the predominant (immune) cells?

A

it means “pus-producing”; predominant cells are neutrophils

68
Q

Some of the most pyogenic bacteria are Gram- and Gram+ ____.

A

cocci

69
Q

What cells dominate in granulomatous inflammation?

A

macrophages and T cells

70
Q

What is the MOA of granulomatous inflammation?

A

it’s not that the bacteria produce anything to induce granulomas, but rather the antigens stimulate the acquired immune system, which results in sensitized T-lymphocytes and macrophage activity

71
Q

In granulomatous inflammation, macrophages kill most of the bacteria, however some survive and do what?

A

grow within the macrophages in the granuloma

72
Q

What are the 3 major mechanisms by which bacteria can survive intracellularly?

A
  1. inhibition fusion of the phagosome with lysosome
  2. inhibit acidification of the phagosome
  3. escape from phagosome into cytoplasm
73
Q

The invasion of cells by bacteria is dependent on the interaction of specific bacterial surface proteins called ____ and specific receptors belonging to the ____ family.

A

invasins; integrin

74
Q

Why is Listeria monocytogenes cool? Because of the way it moves between cells. How does it move?

A

it aggregates actin filaments on its surface and is propelled in a “sling-shot” fashion, called actin rockets, from one host cell to another

75
Q

What are Yops proteins?

A

Yersinia outer-membrane proteins; they inhibit phagocytosis and cytokine production

76
Q

Genes encoding many virulence factors are located where on the bacterial chromosome?

A

pathogenicity islands

77
Q

What is a major determinant in what organs are affected by a pathogen?

A

receptors on that organ’s cells’ surfaces

78
Q

What is a pseudomembrane?

A

thick, adherent, grayish or yellowish exudates on the mucosal surfaces of the throat in diphtheria and on the colon in pseudomembranous colitis

79
Q

What are toxoids?

A

exotoxin polypeptides that have been treated with formaldehyde (or acid or heat) and have lost their toxicity, but retain their antigenicity (used in protective vaccines)

80
Q

ADP-ribosylation is an MOA of several exotoxins. What is its effect?

A

the addition of adenosine diphosphate ribose to the target protein in a human cell can cause protein inactivation or hyperactivation, either of which can cause symptoms of the disease

81
Q

Which type of secretion system used for secreting exotoxins has been shown to be most virulent?

A

Type III, also called molecular syringe or injectosome

82
Q

What are the 4 mechanisms of action of the bacterial exotoxins?

A
  1. ADP-ribosylation - of target protein, in-/hyper-activates it
  2. superantigen - stimulates overproduction of cytokines
  3. protease - cleaves protein
  4. lecithinase - hydrolyzes lecithin in cell membrane, causes membrane destruction and cell death
83
Q

What are the exotoxins that make good use of the ADP-ribosylation technique?

A

Diphtheria, E. coli, cholera, and pertussis toxins

CMOD- Block1 (36 decks)

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