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Microbio 1010 > Medical Microbiology > Flashcards

Medical Microbiology Flashcards

1
Q

What is the human microbiome?

A

The collection of all the microorganisms living in association with the human body (microflora, microbiota)

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2
Q

What is the number of human cells compared to the number of microorganisms in the body?

A
  • 10^13 human cells

- 10^14 microorganisms

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3
Q

What is the number of genes in the human genome compared to the number of genes in the microbiome?

A
  • 20,000 genes in human genome

- 20,000,000 genes in microbiome

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4
Q

When does colonization of microorganisms begin?

A

Right after birth

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5
Q

Where does the microbiota live?

A

Every exposed area of the body (skin, mucous)

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6
Q

Which parts of the body should be free of microbes?

A

Internal tissues (blood, muscles, organs)

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7
Q

What do the majority of microorganisms living inside the body do?

A

Harmless commensals that produce beneficial products & inhibit growth of pathogens

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8
Q

Which organism protects the female reproductive tract?

A

Lactobacillus acidophilus

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9
Q

What are the 3 different microenvironments of skin?

A
  • Dry
  • Moist
  • Subcutaneous
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10
Q

What does higher moisture and warmer temperature skin allow for?

A

More microbes to grow

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11
Q

What are the 2 most common types of bacteria found on dry skin?

A

Betaproteobacteria & corynebacteria

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12
Q

What does corynebacterium diphtheriae cause?

A

Cutaneous diphtheria

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13
Q

What are the 2 most common types of bacteria found on moist skin?

A

Corynebacteria & staphylococci

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14
Q

What is an example of a harmless commensal found on skin?

A

Staphylococcus epidermis

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15
Q

What is an example of a pathogen found on skin and what does it cause?

A
  • Staphylococcus aureus

- Causes boils, abscesses, & wound infections

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16
Q

What are examples of subcutaneous skin?

A

Oily skin around the nose and on the upper chest and back

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17
Q

What is the most common type of bacteria found on subcutaneous skin?

A

Propionibacteria

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18
Q

What are propionibacteria?

A

Anaerobic actinobacteria that produce propionic acid as an end-product of fermentation

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19
Q

What is an example of a bacteria found on subcutaneous skin and what does it do?

A
  • Propionibacterium acnes

- Lives in hair follicles, eats sebum, which causes overgrowth and triggers inflammation/inflammatory acne

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20
Q

What are 2 antimicrobial enzymes found in saliva?

A
  • Lysozyme

- Lacteroperoxidase

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21
Q

What is an example of an aerobic organism found in the mouth and where does it live?

A

Neisseria mucosa, which lives on mucous membranes like the tongue

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22
Q

What is an example of an anaerobic organism that lives in the mouth and what does it do?

A
  • Streptococcus mutans, which is an aerotolerant anaerobe
  • Produce a sticky dextran slime layer that lets it stick to surfaces
  • Produces lactic acid as a fermentation end-product
  • Degrades tooth enamel
  • Can lead to gingivitis
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23
Q

What causes the stomach to be inhospitable to most microbes?

A

Low pH & proteolytic enzymes

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24
Q

What is an example of a microorganism found in the stomach and what does it do?

A
  • Helicobacter pylori
  • Colonizes surface of membrane, protected from stomach acid by mucous
  • Produces endotoxins to trigger inflammation & exotoxins to kill cells in the membrane
  • Cause of stomach ulcers
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25
Q

What type of antibiotics treat stomach ulcers?

A

Tetracycline

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26
Q

Which part of the small intestine has the most bacteria?

A

The part with the most neutral pH

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27
Q

What is an example of an organism found in the small intestine and what are its characterisitcs?

A
  • Enterococcus
  • Gram positive lactic acid bacteria
  • Opportunistic pathogen
  • Can develop antibiotic resistance easily
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28
Q

What microorganism causes nosocomial infections of the small intestine?

A

Enterococcus

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29
Q

Why does the large intestine have an extremely large number of microbes?

A

pH is neutral and environment is anoxic

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30
Q

What type of microbes are commonly found in the large intestine?

A

Anaerobes and facultative aerobes

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31
Q

What is an example of a bacteria found in the large intestine and what are its characteristics?

A
  • E. coli

- Indicator of fecal contamination

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32
Q

What are the largest group of bacteria found in the GI tract?

A

Strict anaerobes from Bacteroides & Clostridium

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33
Q

A high number of this kind of microbe may contribute to obesity and why?

A

Methanogens because they use up a lot of H2 which promotes bacterial fermentation, which makes nutrients available to the host

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34
Q

What was found in germ free mice compared to normal mice?

A

Germ free mice had 40% less body fat

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35
Q

What happened when germ free mice were inoculated with microbes compared to healthy mouse intestines?

A

Inoculated mice quickly gained weight

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36
Q

What was the difference in microbes between normal weight mice and genetically obese mice?

A

Genetically obese mice had fewer Bacteroidetes, more Firmicutes, and way more methanogens

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37
Q

What can changing the microbiota of the large intestine do to human health?

A

May cause opportunistic pathogens to take over

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38
Q

What happens in antibiotic associated colitis?

A

Clostridium difficile grows and the colon inflames

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39
Q

What can treat antibiotic associated colitis?

A
  • Further antibiotics
  • Probiotics
  • Fecal transplant
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40
Q

What are the 3 most common bacteria found in the upper respiratory tract?

A
  • Staphylococci
  • Streptococci
  • Carynebacteria
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41
Q

What mucosal tissue are usually free of microorganisms? (2)

A
  • Lower respiratory tract

- Upper urinary tract

42
Q

What kind of bacteria is found in the urethra?

A

Gram negative

43
Q

What happens when some members of the normal microbiota are transferred to the urinary tract and what is an example of this?

A
  • Can act as opportunistic pathogens

- E. coli causes urinary tract infections

44
Q

What happens if the normal microbiota of the female reproductive tract is disturbed?

A

Yeasts can overgrow and cause yeast infections

45
Q

What is an infection?

A

Growth of microbes that are not normally present in the host (does not necessarily mean host is harmed)

46
Q

What is a disease?

A

Damage or injury that impairs regular host function

47
Q

What is a pathogen?

A

Microbe that causes a disease

48
Q

What is an opportunistic pathogen?

A

Microbe that causes disease only in the absence of normal host resistance

49
Q

What are 2 examples of opportunistic pathogens and what do they cause?

A
  • Streptococccus pneumoniae causes pneumonia in immunocompromised patients
  • E. coli causes UTIs when bacteria from feces are moved into urethra
50
Q

What is pathogenicity?

A

Ability to cause a disease

51
Q

What is virulence?

A

Severity of the disease that is caused

52
Q

What is an LD50 value?

A

Number of cells of a pathogen that will cause death in 50% of infected animals

53
Q

What is an ID50 value?

A

Number of cells needed to infect animals (not kill)

54
Q

If bacteria is in your body are you considered infected?

A

NO

55
Q

What are 2 examples of LD50 values?

A
  • Streptococcus pneumoniae LD50 = 50 cells

- Salmonella enterica LD50 = 5000 cells

56
Q

What is pathogenesis?

A

The process by which a disease develops

57
Q

What are virulence factors?

A
  • Genetically encoded traits that contribute to a pathogen’s ability to cause disease
  • The ability of a pathogen to stick to a surface and begin colonization
58
Q

What are 2 examples of non-covalent virulence factors?

A

Slime layers & capsules

59
Q

What are adhesins?

A

Specific surface molecules that allow selective adherence to a particular cell type

60
Q

What does streptococcus mutans use a slime layer for?

A

To stick to teeth and form a biofilm

61
Q

What does streptococcus pneumoniae use a capsule for?

A
  • To stick to cells in lungs

- Protect cell from phagocytes

62
Q

What do strains of enterotoxigenic E. coli use fimbriae for?

A

Adhere specifically to cells in the small intestine

63
Q

What does neisseria gonorrhoeae use fimbriae for?

A
  • Allow it to attach to mucosal epithelial cells

- Retract to bring bacteria close to membrane

64
Q

What is invasiveness?

A

Ability of a pathogen to enter into host cells or spread through tissues

65
Q

What are siderophores?

A

Iron binding molecules

66
Q

What host proteins can sequester iron and make it unavailable for the microorganism?

A

Transferrin & lactoferrin

67
Q

What do siderophores do?

A

Rip iron out of tissues to be used by bacteria

68
Q

What are exoenzymes?

A

Excreted by bacteria to degrade host tissues

69
Q

What does hyaluronidase do and what does this cause?

A
  • Hydrolyzes hyaluronic acid which holds animal cells together
  • Allows pathogen to spread between cells
70
Q

What does collagenase do and what does this cause?

A
  • Degrades collagen, which is a structural component of connective tissue
  • Allows pathogen to spread through tissues
71
Q

What do proteases, nucleases, & lipases do?

A

Degrade host macromolecules

72
Q

What does fibrinolysin do?

A

Dissolves fibrin clots

73
Q

Which microorganism makes streptokinase?

A

Streptococcus pyogenes

74
Q

What does coagulase do?

A

Induces fibrin clots

75
Q

Which microorganism produces coagulase and why?

A

Staphylococcus aureus to protect it from phagocytes

76
Q

What are invasins?

A

Proteins that allow bacteria to invade and directly enter into host cells

77
Q

What is an example of a microorganism that produces invasins and why does it produce them?

A

Listeria monocytogenes to promote phagocytosis by macrophages, allowing it to spread from cell to cell

78
Q

What are characteristics of Listeria monocytogenes?

A
  • Non-lactic acid
  • Non-spore forming
  • Psychrotolerant
  • Member of Firmicutes
79
Q

Where can Listeria monocytogenes be found?

A

In unpasteurized dairy products & improperly packaged processed meats

80
Q

What does bacteremia mean?

A

Bacteria in the blood

81
Q

What does septicemia mean and what can it lead to?

A
  • Bacteria multiplying in the blood

- Can lead to sepsis (widespread systemic inflammation)

82
Q

What type of bacteria generally causes septic shock?

A

Gram negatives, but sometimes by Gram positives

83
Q

What do proteins that are released by growing bacteria do?

A

Inhibit host cell function (or kill host cells)

84
Q

What are some virulence factors found in Bacillus anthracis?

A

Capsule, exoenzymes, and anthrax toxin

85
Q

What are 3 categories of exotoxins?

A

1) Cytotoxins
2) AB toxins
3) Superantigens

86
Q

What do cytotoxins do?

A

Disrupt cytoplasmic membrane integrity

87
Q

What are 3 types of cytotoxins?

A

1) Hemolysins
2) Lecithinase/phospholipase
3) Leukocidins

88
Q

What do hemolysins do?

A

Lyse many cells (not just RBCs)

89
Q

What is an example of a hemolysin and what does it do?

A
  • Streptococcus pyogenes

- Produces streptolysin that attacks sterols in the cell membrane

90
Q

What does lecithinase/phospholipsase do?

A

Dissolve membrane lipids

91
Q

What is an example of a lecithinase/phospholipase?

A

Clostridium perfringens, which is an alpha-toxin

92
Q

What do leukocidins do?

A

Destory WBCs

93
Q

What is an example of a leukocidin and what does it do?

A
  • Staphylococcus auerus which is a staphylococcal alpha-toxin
  • Toxin subunits insert into the membrane and oligomerize to form a heptamer, forming a pore that causes cell contents to leak out and kill the cell
94
Q

What type of subunits are found in AB toxins?

A

Active subunit and Binding subunit (hence AB)

95
Q

What is an example of an AB toxin and what does each of its binding sites do?

A
  • Corynebacterium diphtheriae
  • Subunit B specifically binds to a protein on animal cells
  • Subunit A then moves across the membrane
96
Q

What do superantigens do?

A

Activate T cells to elicit an extreme immune response

97
Q

How do superantigens work?

A
  • Bind to MHC molecules and TCRs outside the antigen binding sites
  • Bridge the gap and mimics proper antigen presentation
98
Q

What are symptoms of superantigens?

A

Extreme fever, systemic inflammation, shock, death

99
Q

What is an example of a superantigen?

A

Staphylococcus aureus’ toxic shock syndrome toxin

100
Q

What is a general example of an endotoxin?

A
  • Lipid A on lipopolysaccharides from Gram negative outer membrane
  • Released when cells die
101
Q

Are endotoxins or exotoxins considered more toxic?

A

Exotoxins

102
Q

What are 2 specific examples of endotoxins and what do they do?

A
  • Salmonellosis – salmonella colonizes intestine; as they die they release endotoxins that cause fever, diarrhea, and generalized inflammation
  • Gram negative sepsis – gram negative bacteria multiply in the blood; when killed by immune system they release endotoxins which leads to massive inflammation causing septic shock and death

Microbio 1010 (8 decks)

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