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Immunology > Microbial Pathogens > Flashcards

Microbial Pathogens Flashcards

1
Q

What are the two classes of virulence factors?

A

Those that facilitate:

  1. microbial invasion
  2. host damage

ex. adhesins, capsules, biofilms, intracellular survival, superantigens, antigenic variation, latency, spores, cysts, exotoxins, endotoxin, antigenic variation, proteolysis of antibodies (extracellular proteases)

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2
Q

What are the 4 factors of invasion by microbial agents?

A
  1. portal of entry
  2. surface colonization
  3. surviving host defenses
  4. portal of exit and transmission to a new host
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3
Q

What are the primary portals of entry?

A
  1. skin
  2. mucosal membrane
  3. organ transplants/blood transfusion
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4
Q

What two means of adhesion do pathogens use to colonize the surface of a portal of entry?

A
  1. adhesins

2. bind to host receptors (hijack)

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5
Q

What are 4 ways pathogens survive in the cell?

A
  1. inhibit lysosome fusion with phagosome
  2. escape into cytoplasm
  3. resist lysosomal enzymes
  4. inhibit phagocytes’ oxidative pathway (prevent oxidative burst)
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6
Q

Give an example of a pathogen that survives host defenses via immunosuppression:

A

HIV

depletes CD4+ T cells

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7
Q

Give an example of a pathogen that survives host defenses by diverting lymphocyte function through stimulation of immune system in nonproductive ways:

A

Streptococcus pyogenes and superantigens: stimulate nonspecific T cell response

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8
Q

What is an example of a protein that prevents opsonization of a pathogen?

What is an example organism that produces this protein?

A

Protein A- binds IgG on ‘wrong end’ of Fc

ex. Staphylococcus spp.

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9
Q

List the portals of exit:

A
  • Skin
  • Mucosal membrane: resp tract, GI tract, Genital tract, Conjuntiva, Urinary tract
  • Organ transplants/blood transfusion
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10
Q

What are the modes of transmission?

A
  • Contact (direct, indirect, fecal-oral)
  • Droplet (2 metres)
  • Airborne
  • Vector-borne
  • Common vehicle (same needle)
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11
Q

What are two main strategies of transmission used by pathogens (to enhance being passed from host to host)? Give examples of each and organisms that use these.

A
  1. Exaggerate host response:
    - cough, sneeze: mycobacterium tuberculosis, influenza viruses
    - rhinorrhea: common cold viruses
    - diarrhea: norovirus, salmonella spp., shigella spp. , campylobacter spp.
  2. Increase environmental survival:
    - spores: clostridium difficile
    - cysts: protozoa
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12
Q

What are the 4 main ways microbial agents harm us/cause damage?

A
  1. damage due to host immune response
  2. toxins: exotoxin (secreted into host), endotoxin (lipopolysaccharide in membrane, gram-)
  3. apoptosis
  4. mechanical causes
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13
Q

Are exotoxins usually necessary for bacterial growth?

A

No. They are dispensable (as with the plasmid they are carried on)

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14
Q

What are the 5 main mechanisms of action of exotoxins?

A
  1. help bacteria spread in tissues:
    - streptokinase (streptococcus pyogenes)
    - DNase (staphylococcus aureus)
    - hyaluronidase (S. aureus, S. pyogenes)
  2. lyse cells:
    - leukocidins (S. aureus)
    - hemolysins (S aureus, S pyogenes)
    - lecithinase (clostriudium perfringens)
  3. block protein synthesis
  4. elevate/suppress normal cell function:
    - clostridium tetani (tetanus toxin), clostridium botulinum (botulism toxin)
  5. block nerve functions
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15
Q

How does tatanus toxin work?

A

Retrograde transport to spinal cord (CNS)–> inhibits GABA–> rigid muscle contraction (resp muscles)–> death

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16
Q

How does botulinum toxin work?

A

Blocks release of ACh at NMJ (peripheral nerve endings)–> irreversible relaxation of muscles–> paralysis and resp arrest

17
Q

How do we prevent and treat the effects of exotoxins?

A
  • immune protection: vaccination with toxoids ex. tetanus, diptheria
  • treatment with antitoxins ex. tetanus, diptheria, botulism
18
Q

How to the endotoxins on GN bacteria work to cause host damage?

A

lipopolysaccharide on outer membrane of GN bacteria–>

Low levels: interacts with phagocytes–> cytokine release–> fever, vasodilation

High levels: alarming cytokine response–> septic shock and intravascular coagulation (lethal)

19
Q

What is an example of a organism that blocks apoptosis of host cells (immortalize cells)

A

Human papillomavirus

20
Q

What are 2 examples of organisms that cause premature apoptosis in host cells?

A
  • herpesviruses

- HIV

21
Q

What kind of organisms can cause host damage via mechanical mechanisms (think BIG!)

A

helminths that cause obstruction:

heavy infestation with large roundworm ‘Ascaris’ (15-35 cm long, 0.5 cm thick)–> occludes intestinal lumen

22
Q

What are the 2 major groupings of pathogens (disease causing microorganisms)?

A
  1. opportunistic pathogens

2. true pathogens

23
Q

What is the difference b/w opportunists and true pathogens?

A

Opportunists have no/few virulence factors (wouldn’t infect if not for opportunity ie break in host defense)

True pathogens have many virulence factors

(*this is a spectrum)

24
Q

Where is normal flora found (mostly bacteria)?

A
  • skin (esp moist areas)
  • respiratory tract: nose, oropharynx
  • GI tract: mouth, large intestine
  • GU tract: peri-urethra area, vagina
25
Q

List 3 skin commensals/normal flora:

A
  • staphylococcus spp. (GPCA= gram pos cocci aerobe)
  • corynebacterium spp. (GPBA)
  • bacillus spp. (GPBA)
26
Q

List 4 examples of normal oropharynx flora:

A
  • viridans group streptococci (GPCA)
  • neisseria spp. (GNCA)
  • haemophilus spp. (GNCBA)
  • candida spp.
27
Q

List 5 examples of normal large intestine flora:

A
  • enterococcus spp. (GPCA)
  • enteric bacilli/enterobacteriaceae: E coli, Klebsiella spp. (GNBAn)
  • bacteroides spp. (GNBAn)
  • clostridium spp. (GPBA)
  • candida spp.
28
Q

List 4 normal vaginal flora:

A
  • viridans group streptococci (GPCA)
  • peptostreptococcus spp.
  • lactobacillus spp.
  • candida spp.
29
Q

What are the benefits of the normal flora in our bodies?

A
  • immune stimulation (cross-reaction bw Ab to normal flora and virulent organisms)
  • infection prevention (competition, produce inhibitory substances)
  • human nutrition (GI bact flora: e coli, bacteroides spp.)–> synthesize vitamin K
  • digestion
30
Q

List 10 main organisms that make up the normal microbial flora (our friends…unless opportunity presents to be our enemies):

A
  • Staphyloccocus spp.
  • Streptococcus spp.
  • Enterococcus spp.
  • Corynebacterium spp.
  • Bacillus spp.
  • Escherichia coli
  • Haemophilus spp.
  • Neisseria spp.
  • Clostridium spp.
  • Bacteroides spp.

Immunology (32 decks)

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