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CSMLS > MICRO Enterics > Flashcards

MICRO Enterics Flashcards

1
Q

Common genera of Enterobacteriaceae that are pathogenic

A
  • Klebsiella
  • Shigella
  • Salmonella
  • Escherichia
  • Proteus
  • Citrobacter
  • Serratia
  • Yersinia
  • Enterobacter
  • Providencia
  • Morganella
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2
Q

Normal flora in the gastrointestinal tract

A
  • Enterobacteriaceae
  • CNS
  • Anaerobes
  • Diphtheroids
  • Enterococcus sp.
  • Candida sp.
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3
Q

Obligate pathogens in the GI

A
  • Salmonella enterica
  • STEC; E.coli O157:H7
  • Yersinia enterocolitica
  • Shigella sp.
  • Campylobacter jejuni
  • Vibrio cholerae
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4
Q

Which pathogens are implicated in food poisoning/ food toxemias (5)?

A
  • S. aureus
  • B. cereus
  • Clostridioides difficile
  • C. perfringens
  • C. botulinum
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5
Q

Which bacteria is associated with gastric, peptic and duodenal ulcers ?

A

Helicobacter pylori

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6
Q

Salmonella on MAC and HEK

A

MAC: wh
HEK: translucent blue-green +/- black center

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7
Q

Shigella on MAC and HEK

A

MAC: wh
HEK: translucent green

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8
Q

Yersinia on MAC and HEK

A

MAC: wh
HEK: pink/yellow

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9
Q

Yersinia on CIN

A

Cefsulodin Irgasan Novobiocin:
- “bulls-eye;” translucent with red center

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10
Q

E. coli O157:H7 on SORB/SMac and CHROMagar Stec

A

colorless

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11
Q

Campylobacter on CBF

A

Campylobacter Blood Free:
- gy, moist, fltspr, or raised

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12
Q

Describe Principle of Tube Indole

A
  • bacteria capable of hydrolyzing tryptophan (in peptone water) to form indole ?
  • detected by colour rxn with dimethylamino benzaldehyde (Kovac’s)
  • tube test could also check for motility before adding Kovac’s by performing a wet mount
  • differentiates lactose fermenters:
    a). E. coli = POS
    b). Klebsiella oxytoca (POS) vs K. pneumoniae (NEG)

red = POS

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13
Q

What is the general rule for order of inoculation of media plates and biochemicals ?

A
  • liquid to solid
  • least selective to most selective
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14
Q

What is the purpose for CNA ?

A

Colistin Naladixic Acid:
- selects for gram POS bacteria
- inhibits gram neg, normal flora
- enhances beta hemolysis

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15
Q

What is the purpose of PEA when incubated anaerobically ?

A
  • isolates strict anaerobes
  • facultative gram neg anaerobes (ie. Enterobacteriaceae) DO NOT GROW
  • gram pos will grow (S. aureus)
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16
Q

Which planting media is used for a spot indole ?

A

BAP or CHOC; tryptophan is present

17
Q

Describe Principle of Spot Indole

A
  • more sensitive than tube indole
  • can’t check for motility first
  • useful for organisms that won’t grow in peptone water (anaerobes)
  • colony transferred to filter paper; saturated w/ spot indole reagent (p-dimethylaminocinnanaldehyde);
  • blue/green = POS
  • pink = neg
18
Q

List 2 conditions that must be met for decarboxylation to occur. Why is a control tube needed ?

A
  1. Acidic (due to decarboxylation of amino acids)
  2. Anaerobic (mineral oil)
    - control tube ensures that color change = decarboxylation
19
Q

Describe CHROMagar STEC media. Why do Shiga-Toxin-producing organisms need to be identified ?

A

CHROMagar STEC:
- selective and differential
- qualitative, direct differentiation of Shiga-like toxin producing E. coli
- toxic shock syndrome is fatal

20
Q

3 sugars (%) in TSI

A

Sucrose (1.0%) - slant
Lactose (1.0%) - slant

Glucose (0.1%) - butt

21
Q

Which organism is a sick A/A on TSI ?

A

Yersinia enterocolitica

22
Q

Tube indole reagent

A

(Kovac’s) Dimethyl benzaldehyde

23
Q

What is Cary-Blair media for ?

A
  • transport of rectal and fecal specimens
  • preserves enteric pathogens
24
Q

T or F: toxins of C. perfringen causes fever and vomiting

A

FALSE; C. perfringen DOES NOT cause fever and vomiting

25
Q

Oxidase Prinicple

A
  • oxidation of colourless TMPD = dark PURPLE indophenol
  • result depends on the presence of cytochrome C (bacteria whose ETC has cytochrome c oxidase)
26
Q

This media may inhibit oxidase activity and thus should not be used when doing an oxidase test

A

MAC

27
Q

A differential medium, used as a screen test for enteric pathogens on the basis of carbohydrate fermentation, HS production, and gas production

A

Triple Sugar Iron (TSI)

28
Q

Triple Sugar Iron (TSI)

A

A differential medium, used as a screen test for enteric pathogens on the basis of carbohydrate fermentation, HS production, and gas production

Sucrose/ lactose = slant
Glucose = butt

Fermentation = yellow (A)
No fermentation = red (K)

29
Q

Citrate utilization

A
  • organism uses citrate as their sole source of carbon
  • pos = growth (blue due to alkaline end products produced)
  • useful for differentiation of lactose fermenters
    (Kleb and Enterobacter utilize citrate but E. coli does not)
30
Q

Medium method for motility is not useful for these organisms

A

STRICT AEROBES like Pseudomonas will not grow in the depth of medium (use microscopic examination)

CSMLS (46 decks)

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