Anaerobes Flashcards

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1
Q

3 ways to determine MIC

A

E test
Agar dilution
Broth microdilution

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2
Q

How does MacConkey stop the growth of gram positive organisms

A

Bile salts and crystal violet

Can get them without the crystal violet to allow for the growth of Strep

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3
Q

Ecchymosis

A

Bruising not due to trauma

Blood pools under the skin

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4
Q

Crepitus

A

Gas

Can press on the tissue and it sounds like you’re bursting bubbles

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5
Q

2 clues to tell it is Clostridium perfringins on a microscope slide

A
  1. Big gram positive bacilli

2. No neutrophils in sample (it produces a toxin that destroys leukocytes)

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6
Q

What is the difference in paralysis between botulism and tetanus?

A

Botulism: flaccid paralysis
Tetanus: rigid paralysis

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7
Q

3 possible mechanisms of why anaerobic bacteria cannot grow in the presence of oxygen

A
  1. No cytochrome systems for the metabolism of O2
  2. Little/no superoxide dismutase
  3. Little/no catalase
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8
Q

3 enzymes required for oxygen metabolism

A

Catalase
Superoxide dismutase
Peroxidase

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9
Q

3 methods for excluding oxygen to grow anaerobes

A
  1. Liquid media containing fresh animal tissue or 0.1% agar containing a reducing agent, thioglyocollate
  2. Anaerobic jar: gas packs (has sodium bicarb and sodium borohydride that eat up all the oxygen) or gas replacement (computerized pump that sucks out all the air and replaces it with an inert gas)
  3. Anaerobic chamber
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10
Q

What colour is methylene blue with or without oxygen

A

Aerobic: blue
Anaerobic: colourless

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11
Q

Do aerobes raise or lower the redox potential?

A

They consume O2 and LOWER the redox potential

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12
Q

What does B. fragilis do? (2)

A

Synthesizes vitamin K

Conjugates bile acids

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13
Q

6 Clinical features of anaerobic infections

A
  1. Source is usually endogenous flora
  2. Alterations of hosts tissue provides suitable conditions for opportunistic infections
  3. Typically polymicrobial
  4. Abscess formation
  5. Exotoxin involvement
  6. Smells really bad
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14
Q

6 factors that predispose patients for anaerobic infections

A
Trauma to mucosal membranes or skin
Interruption of blood flow
Tissue necrosis
Decrease in redox potential in tissues
Prior antibiotic therapy
Immuno-suppression
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15
Q

7 Anaerobic virulence factors

A
  1. Polysaccharide capsule
  2. Adherence factors
  3. Toxins
  4. Hyaluronidase
  5. Lipases
  6. Enzymes (ex: proteases, phospholipases)
  7. Necrotizing toxins
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16
Q

7 Indications of anaerobic infections

A
  1. Usually purulent
  2. Close proximity to mucosal surface
  3. Infection persists despite antibiotic therapy
  4. Presence of foul odor
  5. Presence of large quantities of gas
  6. Presence of black colour or brick red fluorescence
  7. Distinct morphologic characteristics in gram stained preparation
17
Q

A double zone of hemolysis is typical for which organism?

A

Clostridium perfringins

18
Q

What two genera form spores? Are they aerobic or anaerobic?

A

Clostridium (anaerobic)

Bacillis (aerobic)

19
Q

Hyaluronidase function

A

Allows the bacteria to have disseminating infections

Breaks down connective tissue so it can spread