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Medical Microbiology > Lecture 14 > Flashcards

Lecture 14 Flashcards

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1
Q

How do microorganisms enter a host?

A
  • mucous membranes
  • skin
  • parenteral route (deposited directly into tissues when barriers are penetrated)
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2
Q

What is ID50?

A

infectious dose for 50% of a sample population
- measures virulence of microbe

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3
Q

What is the portal of entry and ID50 for bacillus anthracis?

A

skin: 10-50 endospores
inhalation: 10k-20k endospores
ingestion: 250k-1m

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4
Q

What is LD50?

A

lethal dose for 50% of a sample population
- measures potency of a toxin

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5
Q

What does lower LD50 values indicate?

A

higher toxicity or virulence
- takes a smaller dose to kill 50% of the population

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6
Q

What does a higher LD50 value indicate?

A

lower toxicity
- larger dose is required to kill 50% of the population

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7
Q

What is the LD50 of botulinum?

A

0.03 ng/kg

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8
Q

What is the LD50 of shiga toxin?

A

250 ng/kg

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9
Q

What is the LD50 of staphylococcal enterotoxin?

A

1350 ng/kg

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10
Q

What is adherence?

A

almost all pathogens attach to host tissues

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11
Q

What are adhesins?

A

ligands on the pathogen that bind to receptors on the host cells
- glycocalyx
- fimbriae

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12
Q

What do capsules do?

A

impairs phagocytosis

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13
Q

Give examples of bacteria and the diseases they lead to.

A
  • streptococcus pneumoniae: pneumonia
  • Haemophiles influenzae: pneumonia and meningitis
  • bacillus anthracis: anthrax
  • Yersinia pestis: plague
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14
Q

Where is glycocalyx found?

A

around the cell wall

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15
Q

What is in the cell wall? What are each of their functions?

A
  • M protein resists phagocytosis
  • Opa protein allows attachment to host cells
  • Waxy lipid (mycolic acid) resists digestion
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16
Q

What does coagulase do?

A

coagulates fibrinogen

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17
Q

What do kinases do?

A

digests fibrin clots

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18
Q

What does hyaluronidase do?

A

digests polysaccharides that hold cells together

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19
Q

What does collagenase do?

A

breaks down collagen

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20
Q

What does IgA protease do?

A

destroys IgA antibodies

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21
Q

What is legionella pneumophila? How is it contracted?

A
  • causes pneumonia
  • infects lungs through inhalation (would not survive any other way of transmission)
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22
Q

What is bacillus anthracis? What are the ports of entry?

A
  • causes anthrax
  • skin, inhalation, ingestion
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23
Q

What are invasins? What do they cause?

A
  • surface proteins produced by bacteria that rearrange actin filaments of the cytoskeleton
  • cause membrane ruffling
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24
Q

What bacteria uses actin to move from one cell to the next?

A

shigella
listeria

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25
Q

How do bacteria survive inside phagocytes?

A
  • low pH in phagolysosome
  • escape from phagosome before lysosomal fusion
  • prevention of fusion of lysosome with phagosome
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26
Q

How do biofilms help evade phagocytes?

A
  • biofilm bacteria is more resistant to phagocytosis
  • shielded by extracellular polymeric substance of biofilm
27
Q

What nutrient is needed for most pathogenic bacteria?

A

iron

28
Q

What are siderophores?

A

proteins secreted by pathogens that bind iron more tightly than host cells

29
Q

What are examples of direct damage?

A
  • disrupts host cell function
  • uses host cell nutrients
  • produces waste products
  • multiplies in host cells and causes ruptures
30
Q

What are toxins?

A

poisonous substances produced by microorganisms

31
Q

What can toxins cause?

A

fever, cardiovascular problems, diarrhea, shock

32
Q

What is toxigenicity?

A

ability of a microorganism to produce a toxin

33
Q

What is toxiemia?

A

presence of toxin in the host’s blood

34
Q

What is intoxication?

A

presence of toxin without microbial growth

35
Q

What are exotoxins? What do they do?

A

proteins produced and secreted by bacteria
- soluble in bodily fluids
- destroys host cells
- inhibits metabolic functions

36
Q

What are antitoxins?

A

antibodies against specific exotoxins

37
Q

What are toxoids?

A

inactivated exotoxins used in vaccines

38
Q

What do genotoxins damage? What does this cause?

A

damages DNA
- causes mutations
- disrupts cell division
- leads to cancer

39
Q

Why do superantigens cause an intense immune response? What are symptoms they cause?

A
  • release of cytokines from host cells (T cells)
  • causes fever, nausea, vomiting, diarrhea, shock, death
40
Q

What is each component on a A-B toxin?

A

A: enzyme
B: binding component

41
Q

What do leukocidins do?

A

kill phagocytic leukocytes

42
Q

What do hemolysins do?

A

kill erythrocytes by forming protein channels

43
Q

What do streptolysins do?

A

same as hemolysins (kill erythrocytes by forming protein channels)
- just produced by streptococci instead

44
Q

What are endotoxins?

A

portion of lipopolysaccharides of gram-negative bacteria (lipid)

45
Q

When are endotoxins released? What do they do?

A

released during bacterial multiplication and when gram-negative bacteria die
- stimulate macrophages to release cytokines
- cause disseminated intravascular coagulation

46
Q

What test is used for endotoxins?

A

limulus amebocyte lysate assay (LAL)
- horseshoe crab blood

47
Q

How does the LAL assay work?

A

amebocytes lyse in the presence of endotoxins and produce a clot

48
Q

What do plasmids carry?

A

genes for toxins, production of antibiotics and enzymes

49
Q

What is lysogenic conversion?

A

changes characteristics of a microbe due to incorporation of a prophage

50
Q

What are some examples of cytopathic effects?

A
  • stopping cell synthesis
  • causing cell lysosomes to release enzymes
  • creating inclusion bodies in the cell cytoplasm
  • fusing cells to create a syncytium
  • changing host cell function or inducing chromosomal changes
  • inducing antigenic changes on the cell surface
  • loss of contact inhibition in the cell, leading to cancer
51
Q

What are alpha and beta interferons produced by? What do they do?

A

produced by virally-infected cells
- protects neighboring cells from viral infection
- inhibits synthesis of viral proteins and host cell proteins
- kill virus-infected host cells by apoptosis

52
Q

What is fungi? What can they cause?

A

toxic metabolic product
- can cause allergic response

53
Q

What do trichothecene toxins do?

A

inhibit protein syntehsis

54
Q

What do proteases do?

A

modify host cell membranes

55
Q

What do capsules do?

A

prevents phagocytosis

56
Q

What is ergot?

A

alkaloid toxin that causes hallucinations

57
Q

What is aflatoxin?

A

carcinogenic toxin produced by aspergillus

58
Q

What are mycotoxins?

A

produced by mushrooms and are neurotoxic

59
Q

Give examples of mycotoxins.

A

Phalloidin
Amanitin

60
Q

How do protozoa avoid host defenses?

A
  • digesting cells and tissue fluids
  • growing in phagocytes
  • antigenic variation
61
Q

What are helminths? What do they do?

A

parasitic worms
- use host tissue for growth
- produce large masses
- cause cellular damage
- produce waste products that cause symptoms

62
Q

What neurotoxin can some algae produce?

A

saxitoxin
- paralytic shellfish poisoning

63
Q

What are examples of portals of exit?

A
  • respiratory tract (cough/sneeze)
  • gastrointestinal tract (poop and spit)
  • genitourinary tract (pee and cum)
  • skin
  • blood

Medical Microbiology (21 decks)

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