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A. White- Microbiology > 13&14- Pathogenicity Of Microorganisms > Flashcards

13&14- Pathogenicity Of Microorganisms Flashcards

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1
Q

MOST exotoxins producers are gram _______?

A

Positive

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2
Q

AB exotoxins are composed of two subunits. What are the functions of each subunit?

A
  • A subunit– responsible for toxic effect

- B subunit– binds to specific target cell

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3
Q

Are endotoxins heat labile or heat stable?

A

Heat stable

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4
Q

Where are endotoxins coming from?

A

Lipopolysaccharide (LPS) portion in gram-negative cell wall.

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5
Q

Streptococcus pyogenes contains __________ in its cell wall which helps it to resist phagocytosis?

A

M protein

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6
Q

Neisseria gonorrhoeae contain _________ in its cell wall to inhibit T hyper cells?

A

Opa protein

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7
Q

These organisms utilize capsules to prevent phagocytosis?

A
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Bacillus anthracis
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8
Q

What are the five main modes of pathogen transmission?

A
  • airborne
  • contact
  • vehicle
  • vector borne
  • vertical
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9
Q

The greater the ability for a pathogen to survive outside the host, the _________ virulent the pathogen is?

A

More

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10
Q

Infectious dose 50 (ID 50)?

A

The number of pathogens that will infect 50% of an experimental group of hosts in a specified time

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11
Q

Lethal dose 50 (LD 50)?

A

The dose that kills 50% of experimental animals within a specified period

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12
Q

Toxigenicity?

A

Ability to produce toxins

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13
Q

Primary (frank) pathogen?

A

Pathogen that causes disease by direct interaction with a healthy host

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14
Q

Opportunistic pathogen?

A

Pathogen that may be part of normal flora and causes disease when it has gained access to other tissue sites or host is immunocompromised

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15
Q

Vector?

A

Organisms that spread disease from one host to another

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16
Q

Zoonoses

A

Diseases transmitted from animals to humans

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17
Q

SIgns?

A

Objective (measurable) changes in the body that can be directly observed

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18
Q

Symptoms?

A

Subjective changes experienced by the patient (you cannot measure something the patient feels)

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19
Q

Virulence factors?

A
  • allow for a pathogen to outcompete host cells and resist their defenses
  • determine the degree to which the pathogen causes damage, invasion, infectivity
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20
Q

What is an example of a superantigen?

A

Staphylococcal enterotoxin B

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21
Q

List some of the general system effects caused by endotoxins.

A
  • fever
  • weakness
  • diarrhea
  • inflammation
  • intestinal hemorrhage
  • fibrinolysis— the enzymatic breakdown of fibrin, the major protein component of blood clots
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22
Q

Mycobacterium tuberculosis contain _________ in its cell wall which helps resist digestion?

A

Mycolic acid (waxy lipid)

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23
Q

Coagulase?

A

Coagulates fibrinogen

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24
Q

Kinases?

A

Digest fibrin clots

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25
Q

Hyaluronidase?

A

Hydrolyzes hyaluronic acid (found in connective tissue)

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26
Q

Collagenase?

A

Hydrolyzes collagen

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27
Q

IgA proteases?

A

Destroy IgA antibodies

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28
Q

Exposure to a pathogen alone is not sufficient enough for an infection to occur. Rather, the pathogen must also make contact with the appropriate host tissue. This specificity is known as?

A

Tropism

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29
Q

Airborne transmission?

A

The pathogen is suspended in the air in droplets, droplet nuclei, or dust, which travel over a meter or more from the source to the host.

  • Usually results from host-to-host interaction (coughing, sneezing)
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30
Q

The coming together or touching of source/reservoir and host could be termed?

A

Contact transmission

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31
Q

Direct contact transmission (person-to-person)?

A
  • physical interaction between source/reservoir and host

- e.g., kissing, touching, and sexual contact

32
Q

Indirect contact transmission?

A
  • involves an intermediate (usually inanimate)

- e.g., eating utensils, bedding

33
Q

Droplet spread contact transmission?

A
  • large particles (>5um) that travel
34
Q

Vehicle?

A

Inanimate materials or objects involved in pathogen transmission

35
Q

Common vehicle transmission?

A
  • single vehicle spreads pathogen to multiple hosts

- e.g., water and food

36
Q

Fomites?

A
  • common vehicles such as surgical instruments, bedding, and eating utensils
37
Q

External (mechanical) transmission?

A
  • passive carriage of pathogen on body of vector

- no growth of pathogen during transmisison

38
Q

Internal transmission?

A
  • carried within vector
  • harborage transmission– pathogen does not undergo changes within vector
  • biologic transmission– pathogen undergoes changes within vector
39
Q

Vertical transmission?

A

Occurs when the unborn child acquires a pathogen from an infected mother

  • Does not occur as frequently as horizontal transmission
40
Q

List some examples of diseases acquired by vertical transmission (4).

A
  • gonorrhea
  • herpes
  • German measles
  • toxoplasmosis
41
Q

Bacillus anthracis is more virulent through which of its 3 portals of entry?

A

Through the skin!

  • ID50 through the skin is 10-50 endospores
  • ID50 for inhalation is 10,000 to 20,000 endospores
  • ID50 for gastrointestinal anthrax is ingestion of 250,000 to 1,000,000 endospores
42
Q

Name the two main factors responsible for host susceptibility to a pathogen.

A
  • defense mechanism of the host (innate and adapted/acquired immunity)
  • pathogenicity of pathogen
43
Q

List some of the portals of exit for a pathogen (5).

A
  • respiratory tract (coughing and sneezing)
  • gastrointestinal tract (feces and saliva)
  • genitourinary tract (urine and vaginal secretions)
  • skin
  • blood (biting arthropods and needles or syringes)
44
Q

Extracellular pathogens?

A

Grow outside cells in blood, or tissue fluids

45
Q

Intracellular pathogens?

A

Grow and multiply within cells

46
Q

What are the types of intracellular pathogens?

A
  • facultative intracellular pathogens

- obligate intracellular pathogens

47
Q

Which type of pathogen transmission is more virulent, direct contact transmission or vector-born transmission?

A

Vector borne transmission

  • direct contact–> less virulent
  • vector-borne –> highly virulent in human host; relatively benign in vector
48
Q

List some ways that pathogens can resist host defenses (10)

A
  • production of decoy proteins to bind available neutralizing antibodies
  • lengthened O-chains to prevent host detection or lysis
  • hiding inside host cells
  • infection of immune system cells, diminishing function
  • fuse with adjacent cells to prevent exposure to antimicrobial proteins in host
  • capsules prevent phagocytosis
  • mutations change antigenic sites or alter expression of antigens (through down regulation or phase variation—Altered pilin protein, N. gonorrhea)
  • production of substances that resemble host tissues
  • production of proteases that degrade host proteins
  • special proteins that interfere with host defenses
49
Q

These organisms are able to resist host defenses by surviving inside host cells, ejecting themselves from cell to cell using host actin?

A
  • Shigella sp.

- Rickettsia sp.

50
Q

These molecules interact with host molecules and cells, and indirectly activate host systems such as coagulation, complement, fibrinolytic, and kininogen systems?

A

Endotoxins

51
Q

Endotoxin interaction with macrophages causes what?

A

Release of endogenous pyrogens (induces fever)

52
Q

Endotoxin binding to LPS-binding protein causes what?

A

The release of cytokines (tumor necrosis and others lead to septic shock)

53
Q

Superantigens?

A

Toxic bacterial proteins that stimulate the immune system much more extensively than do normal antigens

54
Q

What is the difference between exotoxins and endotoxins?

A

Exotoxins are proteins and endotoxins are lipids

55
Q

Toxin?

A

A specific substance that damages host

56
Q

Intoxications?

A
  • diseases that result from entry of a specific preformed toxin into the host (ex. Tetanus toxin)
57
Q

Toxemia?

A

Condition caused by toxins in the blood of host

58
Q

Bacteremia?

A

The presence of viable bacteria in the blood

59
Q

Septicemia?

A

The presence of pathogens or their toxins in the blood

60
Q

Infectivity?

A

The ability to create a discrete point of infection

61
Q

Invasiveness?

A

The ability to spread to adjacent tissues

62
Q

List some portals of entry.

A
  • skin, respiratory, gastrointestinal, urogenital systems, or conjunctiva of eye, parenteral route
  • arise from: vectors, sexual contact, blood transfusions, or organ transplants
63
Q

Streptococcus mutants adhere to host cell receptors via?

A

Glycocalyx (sugar residues)

64
Q

Escherichia coli adhere to host cell receptors via?

A

Fimbriae (type I)

65
Q

Streptococcus pyogenes adhere to host cell receptors via?

A

M protein

66
Q

What are pathogenicity islands?

A

Major virulence factors on large segments of chromosomal or plasmid DNA

  • increase bacterial virulence
  • absent in non pathogenic members
  • contain common sequence characteristics
  • can be spread through horizontal gene transfer of virulence genes to bacteria
67
Q

What course do infectious diseases follow?

A

Incubation period—>prod romal stage—>period of illness—> convalescence

68
Q

Incubation period?

A

Period after pathogen entry, before signs and symptoms

69
Q

Prodromal stage?

A
  • onset of signs and symptoms

- not clear enough for diagnosis

70
Q

Period of illness?

A
  • disease is most severe, signs and symptoms
71
Q

Convalescence?

A
  • signs and symptoms begin to disappear
72
Q

Disease syndrome?

A

A set of signs and symptoms that are characteristic of a disease

73
Q

Infectious disease cycle (chain of infection)?

A

The linked events that must occur for an infectious disease to be expressed in an individual

  • agent identity
  • virulence of agent
  • means of exposure to agent
  • dose of agent
  • susceptibility of host to agent
74
Q

Parasites are organism that?

A
  • live on or within a host organism and are metabolically dependent on the host
  • are an organism that cause disease
75
Q

Host?

A

Larger organism that supports the survival and growth of a smaller organism

A. White- Microbiology (11 decks)

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