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Kaplan Micro > Ch 1: General > Flashcards

Ch 1: General Flashcards

1
Q

Normal Flora of the cutaneous surfaces of urethra and outer ear

A
  1. staph epidermidis ** most important
  2. Less important:
    - staph. aureus
    - corynebacteria (diphtheroids)
    - streptococci
    - anaerobes ie peptostreptococci, yeasts (candida spp)
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2
Q

Normal Flora of the nose

A
  1. staph aureus
  2. Less important:
    - s. epidermidis
    - diptheroids
    - assorted streptococci
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3
Q

Normal Flora of the oropharynx

A
  1. viridans streptococci ie strep mutans (secretes a biofilm that glues it and other oral flora to teeth, producing dental plaque)
  2. Less important:
    - assorted strep
    - nonpathogenic neisseria
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4
Q

Normal Flora of the gingival crevices

A
  1. anaerobes: bacteroides, prevotella, fusobacterium, streptococcus, actiomyces
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5
Q

Normal Flora of the stomach

A

none

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6
Q

Normal Flora of the colon

A
    • babies: breast-fed only: bifidobacterium
    • Adult: bacteroides/prevotella (predominant organism), escherichia, bifidobacterium
  2. Less important:
    - babies: lactobacillus, streptococci
    - adults: eubacterium, fusobacterium, lactobacillus, assorted gram - anaerobic rods, enterococcus faecalis, other strep
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7
Q

Normal Flora of the vagina

A
  1. lactobacillus
    * Group B strep colonize vagina of 15-20% of women and may infect infant during labor or delivery, causing septicemia and/or meningitis (as may E.coli from fecal flora)
  2. Less important:
    - assorted strep, gram - rods, diphtheroids, yeasts, veillonella
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8
Q

primary mechanism of adherence used by gram - cells

A

pili/fimbriae

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9
Q

primary mechanism of adherence used by gram + cells

A

teichoic acids (basically pili for gram + org)

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10
Q

biofilms are used by

A
  • staph epidermidis
  • strep mutans
  • pseudomonas aeruginosa
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11
Q

Bacterial Ribosome size and subunits

A

70s: 30s + 50s

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12
Q

Fungi Ribosome size and subunits

A

80s: 40s + 60s

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13
Q

Parasite Ribosome size and subunits

A

80s: 40s + 60s

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14
Q

Cell Membrane sterols

  1. virus
  2. bacteria
  3. fungi
  4. parasites
A

Cell Membrane sterols

  1. virus = no membrane
  2. bacteria = no sterols (mycoplasma)
  3. fungi = Ergosterol* major target for anti-fungal drugs
  4. parasites = cholesterol
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15
Q

Cell wall component

  1. virus
  2. bacteria
  3. fungi
  4. parasites
A
  • Cell walls are found in prokaryotes and fungi:
    1. virus = no cell wall
    2. bacteria = peptidoglycan (gram + bacteria have thicker PG cell wall –> can retain crystal violet stain on gram stain; gram - bacteria have thin PG cell wall, can’t retain stain, are pink)
    3. fungi = chitin
    4. parasites = no cell wall
  • DNA with histones, monocistronic mRNA, and 80S ribosomes are found in all eukaryotes.
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16
Q

Prokaryotic or Eukaryotic?

A

bacteria = prokaryotic

fungi and parasites = eukaryotic

17
Q

HY Encapsulated organisms

A 
Some Killers Have Pretty Nice Capsules
S: streptococcus pneumoniae
K: Klebsiella pneumoniae
H: Haemophilus influenzae
P: Pseudomonas aeruginosa
N: Neisseria meningitidis
C: Cryptococcus neoformans (fungus)
* all the rest are bacteria
* anti-phagocytic surface component (inhibits phagocyte uptake)
18
Q

Organisms with capsules/slime layers:

A
  1. anti-phagocytic surface component (inhibits phagocyte uptake)
19
Q

Bacteria that evade intracellular killing

A
  1. TB: inhibits phagosome-lysosome fusion

2. listeria quickly escapes phagosome into cytoplasm before phagosome-lysosome fusion

20
Q

Invasins

A
  • surface proteins that allow an organism to bind to and invade normally non-phagocytic cells, thus escaping the immune system (bc non-killing cells don’t have killing mechanisms, so doesn’t need to fight to survive)
  • ex) yersinia pseudotuberculosis (causes diarrhea)
21
Q

Type 3 Secretion systems

A
  • tunnel from the bacteria to the host cell (macrophage) that delivers bacterial toxins directly to the host cell
  • e. coli
  • salmonella
  • yersinia
  • p. aeruginosa
  • chlamydia
22
Q

cross-ran of bacteria-induced antibodies with tissue antigens –> disease
1. What type of hypersensitivity is this?

A

ex) Rheumatic fever

1. Type 2 hypersensitivity (bc antibodies binding directly to a cell/tissue)

23
Q

prion

A

Prions, or “slow viruses,” are not viruses at all but infectious proteins devoid of nucleic acid.

24
Q

Lipid A

A
  • Lipid A is the toxic component of endotoxin or lipopolysaccharide, which makes up the outer membrane of all gram-negative bacteria.
  • Capsules and exotoxins are produced by some gram-negatives and some gram-positives, but not all.
  • Teichoic acids are possessed by all gram-positives.
25
Q

Which exotoxins causes lysis of cell membranes?

A
  • The alpha toxins of Clostridium perfringens and Staphylococcus aureus are cytolytic and lyse cell membranes.
  • Endotoxin is not an exotoxin but an anatomic part of the gram-negative bacterial envelope
26
Q

Endotoxin

A
  • LPS (part of outer membrane/cell envelope; secreted when kill bug)
  • part of gram-negative outer membrane
  • Toxic portion = Lipid A: generally not released until death of cell.
  • Exception: N. meningitidis, which over-produces outer membrane fragments
  • LPS is heat stable and not strongly immunogenic so it can’t be converted to a toxoid
  • MOA of LPS:
    1. LPS activates macrophages –> release of TNF-α, IL-1 (major mediator for fever), and IL-6
    2. Macrophage activation –> cytokines –> tissue damage
    3. damage to endothelium from bradykinin-induced vasodilation –> shock
    4. coagulation (DIC) is mediate through activation of Hageman factor
27
Q

MOA of LPS:

A
  1. LPS activates macrophages –> release of TNF-α, IL-1 (major mediator for fever), and IL-6
  2. Macrophage activation –> cytokines –> tissue damage
  3. damage to endothelium from bradykinin-induced vasodilation –> shock
  4. coagulation (DIC) is mediate through activation of Hageman factor
    - pt presents with septic shock and has gram - org on blood culture. What caused the shock symptoms? LPS (specifically, Lipid A portion)
28
Q

Exotoxins

A
  • are protein toxins secreted by bacterial cells (some gram +, some gram -)
  • can be modified by chemicals/heat to produce a toxoid that is still immunogenic, but no longer toxic so can be used as vaccine
  • A-B (or 2) component protein toxins:
  • B component binds to specific cell receptors to facilitate the internalization of A
  • A component is the active (toxic) component (often an enzyme such as ADP ribosyl transferase)
  • exotoxins may be subclassed as enterotoxins, neurotoxins, or cytotoxins
29
Q

cytolysins

A
  • lyse cells from OUTSIDE by damaging membrane
  • ex: C. perfringens alpha toxin = lecithinase
  • staph aureus alpha toxin inserts itself to form pores in the membrane

Kaplan Micro (7 decks)

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