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Microbiology Unit 3 > Microbial Mechanisms of Pathogenicity (BE #1) > Flashcards

Microbial Mechanisms of Pathogenicity (BE #1) Flashcards

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1
Q

Describe 3 cases of symbiosis.

A
  1. commensalism: one organism benefits, the other is unaffected.
  2. mutualism: both organisms benefit. Ex. E. coli live in the large intestine of humans. They produce Vit. K that we use to make blood clotting factors.
  3. parasitism: host is harmed, microbe benefits.
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2
Q

What benefit do we gain from E. coli in the gut?

A

They produce Vit K which we use to make blood clotting agents.

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3
Q

Define parasite

A

Host is harmed, microbe benefits.

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4
Q

Does hand washing rid the body of its normal flora?

A

no, reduces it

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5
Q

Does hand washing rid the body of transient flora?

A

yes

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6
Q

Differentiate between contamination, infection & disease.

A

Contamination - microbes are present
Infections - multiplication of any parasitic organism; infection does not always cause disease
Disease - disturbance in the state of health; interferes with normal function

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7
Q

Name internal & external body surfaces that are inhabited by normal flora.

A

eyes, nose, mouth, pharynx, esophagus, trachea, colon, lower urethra, vagina

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8
Q

What is a nosocomial infection?

A

hospital-acquired infection

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9
Q

Name a common bacterial cause of nosocomial infections.

A

Staphylococcus aureus

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10
Q

Name 3 opportunities for infection by opportunistic bacteria.

A
  1. Disrupt normal flora w/antibiotics (ex. vaginal yeast infection)
  2. Improper hygiene (ex. colon flora causing a UTI from improper wiping)
  3. Neisseria meningitides from respiratory tract, causing meningitis
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11
Q

Why is it import for moms to breast feed (from a microbiologist’s perspective)?

A

Breast milk keeps the flora of the baby’s intestinal tract at a protective level. Bifidobacterium metabolizes milk sugars into acetic and lactic acid. This keeps the pH of the intestine inhospitable to many disease-causing microbes, most importantly those causing diarrhea.

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12
Q

Why would a prepubertal girl be at risk for STD’s? Why would a postmenopausal woman be at risk for increased vaginal yeast infections?

A

They are not (yet) producing estrogen which increases the growth of lactobacilli. Lacto keeps the vagina at an acidic level, which is inhospitable to disease-causing microbes.

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13
Q

A place where a pathogenic microorganism is maintained between infections -

A

reservoirs

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14
Q

A healthy person who is a reservoir can be called:

A

a carrier

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15
Q

Give 3 examples of environmental reservoirs.

A

soil - Clostridium tetani
water - Vibrio cholera
food - Clostridium botulinum
house dust

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16
Q

Differentiate between an incubatory carrier & a chronic carrier.

A

Incubatory - a person is contagious during the early symptomless period of the disease

chronic - person who harbors a pathogen for an extended period of time w/o becoming ill

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17
Q

Give example of pathogen that uses soil as a reservoir. What enables it to survive?

A

Clostridium tetani

endospore former

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18
Q

Give example of pathogen that uses dust as a reservoir. How can it survive in such dry conditions?

A

Mycobacterium tuberculosis

waxy envelope

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19
Q

Pathogen that uses water as a reservoir.

A

Vibrio cholerae

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20
Q

Pathogen that uses food as a reservoir.

A

Clostridium botulinum

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21
Q

Define zoonosis and give 3 examples of diseases that use animals as reservoirs.

A

Human disease caused by pathogens that maintain an animal reservoir.
Rabies, Lyme disease, West Nile virus, Hantavirus

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22
Q

Differentiate between ID50 and LD50.

A

ID50 is the infection dose. The # of microbes that must enter the body to establish infection in 50% of test animals

LD50 is the lethal dose. The # of microbes that must enter the body to cause death in 50% of test animals.

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23
Q

Which is more pathogenic? Bacterium A = ID50 of 200. Bacterium B = ID 50 of 100

A

Bacterium B - takes fewer bacterial cells to establish infection.

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24
Q

What is the microbe that causes a specific disease?

A

etiologic agent

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25
Q

inanimate objects involved in disease transmission

A

fomites

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26
Q

Differentiate between perinatal and prenatal transmission. Give example of each.

A

Prenatal - infection acquired across the placenta (HIV, Listeria)

Perinatal - infection acquired when fetus passes through the birth canal (syphilis)

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27
Q

Ex. of disease that can be transmitted horizontally.

A

STD’s - gonorrhea, syphilis

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28
Q

Ex. of disease that can be transmitted by fecal-oral route.

A

Hep A
Rotavirus
Nora virus
cholera

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29
Q

Define parenteral & give example of disease transmitted this way.

A

When a biological arthropod vector introduces pathogens during a skin-penetrating bite or break in the skin.
Hep C
tetanus
HIV

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30
Q

Pathogens attach to specific types of target cells by means of protein molecules called:

A

adhesins

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31
Q

Adhesins are generally found on

A

capsules or pili

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32
Q

Bacteria that can invade deeper tissues are called:

A

invasive

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33
Q

Name 2 groups of bacteria that are intracellular pathogens:

A

Rickettisias

Chlamydias

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34
Q

How are Rickettsia bacteria transmitted?

A
  • Rocky Mtn Spotted Fever & typhus

- arthropod vectors

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35
Q

List the 4 major ways that bacteria cause disease.

A
  1. Exotoxin production
  2. Endotoxin production
  3. Exoenzyme production
  4. Stimulation of the body’s defenses
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36
Q

Exotoxins

A
  • produced by G(+) AND G(-) bacteria
  • Proteins
  • minute amounts can be deadly
  • heat sensitive
  • specific for cells they effect
  • can be neutralized w/antibodies (antitoxins)
  • causes food poisoning (food borne intoxication)
  • produce toxoids from them
  • includes tetanus, Shigella toxin, botulinum, E. coli toxin
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37
Q

Endotoxins

A
  • produced by only G(-)
  • lipolysaccharides
  • heat stable
  • nonspecific for cells they effect
  • don’t stimulate immune system to produce antibodies
  • effects include fever, shock, diarrhea
  • antibodies can increase effects
  • released into environment when bacterial cells die
38
Q

Toxoid is

A
  • a type of exotoxin
  • attenuated (weakened) toxin
  • they’ve lost their disease causing properties
39
Q

Tetanus toxin

A
  • A neurotoxin
  • inhibits release of inhibitory neurotransmitters so that opposing muscles contract at same time-causing rigid paralysis
40
Q

Botulinum toxin

A
  • a neurotoxin

- inhibits nerve impulse to muscle; causes flacid paralysis

41
Q

Diptheria toxin

A
  • a neurotoxin

- Corynebacterium diphtheria - inhibits protein syntesis; gene for exotoxin is found on lysogenized prophages

42
Q

Strep toxin

A
  • a erythrogenic toxin

- Streptococcus pyogenes - damages capillaries under the skin & produces a red rash (Scarlatina / Scarlet fever)

43
Q

Vibrio toxin

A
  • an enterotoxin
  • Vibrio cholerae - binds to plasma membranes of epithelial cells in small intestine
  • leads to severe diarrhea & vomiting
44
Q

Staphylococcal toxin

A
  • an enterotoxin

- Staphyloccocus aureus - staph food poisoning

45
Q

Shigella toxin

A
  • an enterotoxin

- Shigella dysenteriae - bloody diarrhea

46
Q

Differentiate between the 2 types of food borne illness (food poisoning).

A

Infection - bacteria are ingested in the food, multiply in body, producing toxin. Onset takes longer than intoxication

Intoxication - bacteria grow in the good, producing toxin in the food. Onset of illness is quick b/c toxin is already present.

47
Q 
Classify each as due to infection or intoxication:
Eschericia coli
Salmonella typhimurium
Shigella dysenteriae
Staphylococcus aureus
Clostridium botulinum
A 
E. coli - infection
Salmonella typhimurium - infection
Shigella dysenteriae - infection
Staphylococcus aureus - intoxication
Clostridium botulinum - intoxication
48
Q

Exoenzymes

A

produced & then released by bacteria

49
Q

coagulase

A
  • triggers blood clotting mechanism, allowing bacteria protection from immune defenses
  • allows bacteria to hide & multiply in clots

Ex. Staphylococcus aureus

50
Q

streptokinase

A
  • dissolves blood clots so bacteria can spread to other tissues
  • allows bacteria to invade other tissues

Ex. Streptococcus

51
Q

protease

A
  • destroys proteins (ex. antibodies)
  • disables the immune response

Ex. Neisseria gonorrhoeae

52
Q

hyaluronidase

A
  • breaks down glue (hyaluronic acid) that holds cells together in tissue
  • helps bacteria to invade deeper tissues

Ex. Streptococcus

53
Q

catalase

A
  • breaks down toxic hydrogen peroxide into water & oxygen (bubbles).
  • H2O2 -> H2O + O2

Ex. Staphylococcus

54
Q

hemolysins

A

Alpha-hemolysin: partially breaks down hemoglobin leaving a greenish halo around colonies (Streptococcus pneumonia)

Beta-hemolysin: completely breaks down hemoglobin leaving a clear ring around colonies (Streptococcus progenies & Staphylococcus aureus)

Gamma hemolytic: no hemolysis occurs

55
Q

leukocidins

A
  • produced by streptococci & staphylococci
  • damage or destroy certain kinds of leukocytes
  • some diseases may result in a decrease in # of wbc (leucopenia) (Staphylococcus)
56
Q

How does Streptococcus pneumonia cause disease?

A

When it multiplies in the lungs, phagocytes come to combat it. Since the bacteria is protected by a capsule, it’s hard to phagocytize, so more & more white blood cells come to help. Dead bacteria & phagocytes accumulate in the lungs making gas exchange hard and breathing difficult.

57
Q

Describe 3 mechanisms by which viruses cause disease.

A
  1. Lytic cycle - results in lysis of cells
  2. Lysogenic cycle (insertion of provirus in a host’s chromosome) –
    - functional changes - ex. stop hormone production
    - unregulated mitosis - cells divide out of control (HPV)
  3. Cell fusion - adjacent cells fuse to form syncytia (RSV, measles)
58
Q

How do viruses interfere with the “switch” that supposed to turn off mitosis?

A

They insert a provirus in a host’s chromosome.

Ex. HPV, Hepatitis B & C, Epstein Barr Virus (Burkitt’s Lymphoma)

59
Q

Give an example of a virus that causes adjacent cells to fuse, forming a syncytium.

A

RSV [respiratory syncytial virus] causes bronchiolitis

60
Q

List 3 bacterial mechanisms that help bacteria evade host defenses?

A
  1. protection agains phagocytosis ( capsules, surface proteins/M proteins, living inside the wbc)
  2. antigenic variation - some microbes mutate & change their surface antigens
  3. production of exoenzymes
61
Q

Name a bacterial species that can survive a phagocyte’s enzymes & live inside the phagocyte.

A

Mycobacterium tuberculosis

Mycobacterium leprae

62
Q

List 4 exoenzymes that help bacteria to evade host defenses.

A
  1. coagulase
  2. streptokinase
  3. protease
  4. leukocidins
63
Q

Describe antigenic variation & give a bacterial & viral example

A
  • some microbes mutate & change their surface antigens

Ex. Neisseria gonorrhoeae, HIV, cold virus, influenza virus

64
Q

How does HIV evade host defenses?

A

HIV attacks the immune system white blood cells (T lymphocytes & macrophages)

65
Q

How does an envelope help viruses to evade host defenses?

A
  1. Envelopes help to mask them (actually part of the host cell it took when it budded)
  2. Makes it easier for virus to enter the cell (fusion w/the plasma membrane & then virus gets dumped into cytoplasm)
66
Q

ID normal portal of entry & exit:

Bordetella pertussis

A

respiratory droplets

67
Q

ID normal portal of entry & exit:

gonorrhea

A

mucosa of genital tract for both

68
Q

ID normal portal of entry & exit:

herpes

A

mucosa of genital tract for both

69
Q

ID normal portal of entry & exit:

HIV

A

mucosa of genital tract for both

blood/body fluids (parenteral)

70
Q

ID normal portal of entry & exit:

Vibrio cholerae

A

fecal-oral

71
Q

ID normal portal of entry & exit:

hepatitis B

A

mucosa of genital tract

blood/body fluids (parenteral)

72
Q

ID normal portal of entry & exit:

hepatitis A

A

fecal-oral

73
Q

ID normal portal of entry & exit:

Plasmodium (protistan)

A

parenteral (mosquito bite)

74
Q

ID normal portal of entry & exit:

Clostridium tetani

A

parenteral - entry through break in skin - dirty wound

exit - endospores living in digestive tract of livestock - their manure contaminates the soil

75
Q

ID normal portal of entry & exit:

Mycobacterium tuberculosis

A

respiratory system for both

76
Q

ID normal portal of entry & exit:

influenza

A

respiratory system for both

77
Q

ID normal portal of entry & exit:

cold virus

A

respiratory system for both

78
Q

acute

A

develops quickly; runs its course quickly (cold, flu, food poisoning)

79
Q

chronic

A
  • develops more slowly,
  • is usually less severe;
  • persists for a long period of time (Hep B & C, mono)
80
Q

Latent

A
  • has periods of inactivity

- herpes, shingles, HIV

81
Q

Local infection

A

confined to a specific area

82
Q

systemic infection

A
  • generalized infection;

- affects most of body

83
Q

septicemia

A
  • pathogens are present and multiply in blood
84
Q

primary infection

A

initial infection in a previously healthy person

85
Q

secondary infection

A

follows a primary infection (sinus infection following a cold)

86
Q

superinfection

A

secondary infection that results from the destruction of normal microflora and often follows the use of broad-spectrum antibiotics

87
Q

mixed infection

A

caused by several species of organisms present at the same time

88
Q

communicable

A

disease spread from one host to another (flu)

89
Q

noncommunicable

A

disease not spread from one host to another (tetanus)

90
Q

contagious

A

disease that spreads easily from one host to another (chicken pox)

91
Q

How does Corynebacteium diphtheria produce toxins?

A

its prophage has the code for toxin. If the bacterium is not infected with a virus, it doesn’t (can’t) make toxin.

Microbiology Unit 3 (7 decks)

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