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Review / Wrong Answers > DIT review - Micro 1 > Flashcards

DIT review - Micro 1 Flashcards

1
Q

What is the function of lipoteichoic acid, and is it found in gram + or gram - bacteria

A

Gram positive

  • Lipoteichoic acid (contained within peptidoglycan layer)
    • Induce cytokines (IL-1, IL-6, TNF-a)
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2
Q

Which bacteria, + or -, contain outer membrane

What is the function of the outer membrane

A

Gram negative

  • Contains lipopolysaccharide (LPS) endotoxin
    • LPS induces cytokines
    • Vs. Gram (+) which induce cytokines via lipotechoic acid
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3
Q

What is the periplasmic space

Is it in gram + or gram - bacteria

What is located here?

A
  • Periplasmic space
    • Between inner and outer membrane
    • Gram -
    • Location of beta-lactamases
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4
Q

What is the Quellung reaction

A
  • Can determine if a capsule is present via Quellung reaction
    • Add anti-capsular serum to bacteria
    • If capsule is present, it will appear swollen under a microscope
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5
Q

Which 2 bacterial species are spore-forming

A

Bacillus and Clostridium species

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6
Q

What do you call a piece of genetic material seperate from chromosomal DNA in a bacteria?

A

Plasmid

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7
Q

Describe genetic transfer via transformation

A

· DNA is released from a lysed cell and then naked DNA is taken up by a living bacterium

· DNA fragment incorporated into chromosomal DNA

· Adding deoxyribonuclease to environment will degrade naked DNA in the medium à no transformation seen

· Feature of SHiN bacteria:

o Strep pneumo, H. influenza type B, Neisseria

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8
Q

Describe genetic transfer via transposition

A

· Segment of DNA that can self-excise and relocate (to different part of chromosome, to different chromosome, or to plasmid)

· Can transfer antibiotic resistance

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9
Q

Describe genetic transfer via conjucation

A

· One way transfer of chromosomal or plasmid DNA

· Donor cell F factor DNA codes for sex pilus

· Bacteria that lack F factor serve as recipient cell

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10
Q

Describe genetic transfer via transduction

A

· Transfer of DNA by bacteriophage (virus that infects bacteria)

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11
Q

Compare generalized transduction vs. specialized transduction

A
  • Generalized transduction = a “packaging” event
    • Lytic phage infects bacterium, leading to cleavage of bacterial DNA
    • Parts of bacterial chromosomal DNA become packaged in phage capsid
    • Phage infects another bacterium, transferring these genes
  • Specialized transduction = an “excision” event
    • Lysogenic phage infects bacterium
    • Viral DNA incorporates into bacterial chromosome
    • When phage DNA is excised, flanking bacterial genes may be excised with it
    • DNA is packaged into phage capsid and can infect other bacterium
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12
Q

What are the reasons that each of the following bacteria do not gram-stain well:

  • Treponema
  • Mycobacteria
  • Mycoplasma
  • Legionella
  • Rickettsia
  • Chlamydia
A
  • Treponema – too thin
  • Mycobacteria – cell wall has high lipid content
  • Mycoplasma – no cell wall
  • Legionella, Rickettsia, Chlamydia – intracellular
    • Chlamydia also lack classic peptidoglycan because of decreased muramic acid
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13
Q

Which bacteria use Giemsa stain

A
  • Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium
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14
Q

Which bacteria use periodic acid schiff (PAS) stain

A
  • Stains glycogen and mucopolysaccharides
  • Used to diagnose Whipple disease (Tropheryma whipplei)
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15
Q

Which bacteria use Ziehl-Neelson stain

A

Aka carbol fushin stain

  • Acid-fast bacteria
  • Mycobacteria, Nocardia
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16
Q

Which pathogen uses india ink stain

A
  • Cryptococcus neoformans (not a bacteria)
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17
Q

Which pathogens use silver stain

A
  • Legionella
  • Helicobacter pylori
  • Fungi (e.g. Coccidiodides, Pneumocystis jiroveci)
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18
Q

What are the 3 main effects of endotoxin

A

(1) Macrophage activation
(2) Complement activation
(3) Tissue factor activation

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19
Q

Endotoxin-mediated macrophage activation causes production of what substances, which leads to what presentation?

A
  • Production of IL-1 and IL-6
    • Fever
  • Production of TNF-a
    • Fever and hypotension
  • Production of nitric oxide
    • Hypotension
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20
Q

Endotoxin-mediaed complement activation has what effect?

A
  • C3a
    • Histamine release à hypotension and edema
  • C5a
    • Histamine release à hypotension and edema
    • Neutrophil chemotaxis
21
Q

Endotoxin-mediated tissue factor activation has what effect?

A
  • Activation of coagulation cascade
    • DIC
22
Q

Can vaccines be formed against endotoxins or exotoxins and why?

A

Exotoxins

Exotoxins are antigenic and our body can form antibodies against them

23
Q

Describe the MOA of exotoxins in Clostridium Tetani and Botulinum

A
  • Both are proteases that cleave SNARE (required for NT release)
  • Clostridium tetani
    • Toxin prevents release of inhibitory (GABA and glycine) NT from Renshaw cells in spinal cord
    • Spastic paralysis, risus sardonicus, “lockjaw”
  • Clostridium botulinum
    • Toxin prevents release of stimulatory (ACh) signals at NMJ
    • Flaccid paralysis, floppy baby
24
Q

What is the MOA of exotoxin in Corynebacterium diptheriae

A
  • Inactivates elongation factor (EF-2)
  • Pharyngitis with pseudomembranes in throat and severe lymphadenopathy
25
Q

MOA of Shiga and Shiga-like toxin

What bacteria contains Shiga-like toxin

A
  • Inactivates 60S ribosome by removing adenine from rRNA
  • GI mucosal damage = dysentery; HUS via enhanced cytokine release
  • Shiga like toxin = EHEC
26
Q

MOA of exotoxin in psuedomonas aeruginosa

A
  • Inactivates elongation factor (EF-2)
  • Host cell death
27
Q

ETEC heat-labile vs. heat-stable exotoxin MOA

A
  • Heat-labile toxin
    • Overactivates adenylate cyclase = increased cAMP = increased Cl- secretion in gut and H2O efflux
    • THINK: Labile in the Air (Adenylate cyclase)
  • Heat-stable toxin
    • Overactivates guanylate cyclase = increased cGMP = decreased reabsorption of NaCl and H2O in gut
    • THINK: Stable on the Ground (Guanylate cyclase)
  • Causes watery diarrhea
    • Leading cause of traveler’s diarrhea
28
Q

What are the 2 main exotoxins of bacillus anthracis

A

Edema toxin

Lethal factor

29
Q

MOA of anthrax edema toxin

A
  • Mimics the adenylate cyclase enzyme = increased cAMP
  • Edematous borders of black eschar in cutaneous anthrax
30
Q

Effect of anthrax lethal toxin

A
  • Zinc-dependent protease that inhibits mitogen-activated protein kinase signaling, causing apoptosis and multisystem physiologic disruption = necrosis and black eschar
31
Q

MOA of cholera toxin

A
  • Overactivates adenylate cyclase (increased cAMP) by permanently activating Gs = increased Cl- secretion in gut and H2O efflux
  • “Rice water” diarrhea
32
Q

MOA of Pertussis toxin

A
  • Overactivates adenylate cyclase by disabling Gi, impairing phagocytosis to permit survival of microbe
  • Whooping cough
33
Q

MOA of alpha toxin of clostridium perfringens

A
  • Alpha toxin
  • Phospholipase (lecithinase) that degrades tissue and cell membranes
  • Degradation of phospholipids à myonecrosis (“gas gangrene”) and hemolysis (“double zone” of hemolysis on blood agar)
34
Q

MOA of streptolysin O of strep pyogenes

A
  • Streptolysin O
    • Antibodies against toxin (ASO) used to diagnose rheumatic fever
  • Protein that degrades cell membrane
  • Lyses RBCs – contributes to beta-hemolysis
  • Oxygen labile
35
Q

MOA of Toxic shock syndrome toxin (TSST) of staph aurues

A
  • Binds to MHC II and TCR, simultaneously, outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN-y, and TNF-a à shock
  • High fever, hypotension, diffuse rash
36
Q

What is the superantigen toxin of Strep pyogenes

A

Exotoxin A

  • Binds to MHC II and TCR, simultaneously, outside of antigen binding site to cause overwhelming release of IL-1, IL-2, IFN-y, and TNF-a à shock
37
Q

What are the gram + rods

A

Clostridium

Listeria

Bacillus

Corynebacterium

38
Q

What color will Mannitol salt agar turn in the presence of staph aureus

A

yellow

39
Q

When is the MOA of Staph aureus virulence factor Protein A

A

Binds to Fc region of antibodies, inhibiting complement activation and phagocytosis

40
Q

Describe the presentation of scarlet fever

A
  • 1) redness and swelling of tongue – strawberry tongue (chef licking strawberry)
  • 2) pharyngitis – red handkercheif
  • 3) widespread rash that spares the face – gingerbread frosted red except for face
41
Q

What substance is associated with the formation of rheumatic fever

A

M protein (highly antigenic - will create antibodies that will cross react with myosin in the heart)

42
Q

What organism is hippurate positive

A

Group B strep

43
Q

Describe the CAMP test

A

GBS will produve CAMP factor, which will enlarge the area of hemolysis formed by staph aureus

44
Q

Presentation of neonatal Group B strep

A

Meningitis

Sepsis

Pneumonia

45
Q

What is the virulence factor of Strep pneumo that allows it to invade mucosa

A

IgA protease

46
Q

Which vaccine is polysaccharide vs conjugate (the one for children or the one for adults)

A

Adult = only IgM response (mezzanine)

  • Polysaccharide vaccine

Children = IgG response (ground)

  • Conjugate vaccine
47
Q

Presentation of Enterococcus infectin

A

do U <3 Trees

  • U – UTIs
  • Heart – endocarditis
  • Tree – biliary tree infections (recall that it is insoluble in bile)
48
Q

What are the diseases associated with Strep D (Strep Bovis)

A
  • Group D strep – Strep Bovis
    • Colonizes the gut
    • Can cause endocarditis
    • Is associated with colon cancer
      • Anyone who is found to have Strep D, should be screened for colon cancer

Review / Wrong Answers (140 decks)

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