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GI > Micro Lab > Flashcards

Micro Lab Flashcards

1
Q

What is a coliform? Which organisms belong to this group?

A

Lac+ Enterobacteriaceae E. coli, Klebsiella, Enterobacter, Citrobacter, Serratia

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2
Q

All gram - fermenters can ferment:

A

Glucose

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3
Q

Name 4 gram - fermenters

A

Enterobactericeae, Campylobacter, Aeromonas

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4
Q

Endocarditis in IV drug user

A

Pseudomonas

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5
Q

Idole -, Methyl Red -, Voges-Proskauer +, Citrate +

A

Klebsiella or Enterobacter

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6
Q

Name 2 opportunistic gram - non-fermenters

A

Pseudomonas, Actinomyces

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7
Q

Describe tube 0 and give a Ddx

A

Slant and butt are red = no fermentation

Pseudomonas, Actinomyces (gram - nonfermenters)

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8
Q

Describe tube 1 and give a Ddx

A

Butt is yellow = glucose fermented; slant is red = lactose NOT fermented

Shigella

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9
Q

Describe tube D and give a DDx

A

Butt is black = H2S formed; Slant is red = lactose NOT fermented; cracks = gas/H2 produced

Proteus, Salmonella, Citrobacter

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10
Q

Describe tube E and give a DDx

A

Slant is yellow = ferments lactose; butt is yellow = ferments glucose; cracks = gas/H2 formed

Klebsiella, E. coli, Enterobacter

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11
Q

Which could be Shigella?

A

Middle tube

(Yellow butt + red slant + no cracks = ferments glucose only)

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12
Q

Which could be Salmonella?

A

Last tube

(Black butt + gas = H2S and H2 formed)

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13
Q

Contamination of burns

A

Pseudomonas + S. aureus

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14
Q

Which organisms could produce the KAI finding in tube 1?

A

E. coli, Klebsiella, Enterobacter

(Yellow slant + butt + gas = lactose fermented)

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15
Q

Which could be Proteus?

A

Second to last tube

(Black = H2S formed; cracks = gas/H2 formed)

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16
Q

What would E. coli show on an IMViC test? Why would we do this?

A

Idole +, Methyl Red +, Voges-Proskauer -, Citrate -

Test for fecal contamination of water = must differentiate E. coli from Klebsiella and Enterobacter which can naturally grow in water so don’t necessarily mean fecal contamination if present

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17
Q

Corneal infections when abraded by contacts

A

Pseudomonas

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18
Q

A glucose-only fermenter, like ____, would produce which tube?

A

Shigella

Tube 1

(Red slant + yellow butt = only ferments glucose)

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19
Q

External ear infections (swimmer’s ear)

A

Pseudomonas

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20
Q

Which could be Pseudomonas?

A

Tube 2

(Red slant + red butt = no fermentation)

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21
Q

Idole +, Methyl Red +, Voges-Proskauer -, Citrate -

A

E. coli

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22
Q

Which would be Enterobacter? Citrobacter?

A

Enterobacter = tube 4 (yellow butt + slant + cracks = lactose fermenter)

Citrobacter = tube 4 (black + cracks = H2S and H2 formed)

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23
Q

Indole test converts ___ to ___ + ____

A

Tryptophan to indole + ammonia

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24
Q

Dx?

A

Shigella, E. coli

(Red layer on top = indole +)

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25
Q

Which is the positive reaction? Which organisms can produce such reaction?

A

Left = agglutination

Salmonella and shigella

(Positive serological testing = agglutination)

26
Q

On this MacConkey agar medium, name 5 enteric bacteria that could be grown on the left and 7 that could be grown on the right.

A

Red = lac+ = E. coli, Klebsiella, Enterobacter, Citrobacter, Serratia

White = lac- = Shigella, Salmonella, Proteus, Morganella, Yersinia, Edwardsiella, Hafnia

27
Q

Cystic fibrosis patients are prone to lung infections with:

A

Pseudomonas

28
Q

What causes infection in infants and intoxication in adults?

A

C. botulinum

29
Q

Describe the basis for serological testing? For which organisms is this method used, albeit uncommonly?

A

Antiserum w/ antibodies + suspension of organisms –> antigen present –> antibodies bind bacteria –> agglutination of bacterial cells

Shigella and Salmonella

30
Q

____ and ____ are non-motile

A

Shigella and Klebsiella

31
Q

This finding was revealed during surgery after an 11 year old boy presented with fever, RLQ pain, and diarrhea with cramping. Bug?

A

Yersinia

(Acute mesenteric lymphadenitis)

32
Q

Oxidase +

A

Pseudomonas

33
Q

Neonatal meningitis

A

E. coli

34
Q

What would Klebsiella or Enterobacter show on IMViC testing? When would we do this test?

A

Idole -, Methyl Red -, Voges-Proskauer +, Citrate +

Test for fecal contamination of water = must differentiate E. coli from Klebsiella and Enterobacter which can naturally grow in water so don’t necessarily mean fecal contamination if present

35
Q

This organism was grown on MacConkey agar with sorbitol instead of lactose. Dx?

A

EHEC

(Can’t ferment sorbitol = white)

36
Q

Red pigmentation

A

Serratia

37
Q

Non-lactose fermenters

A

Shigella (gluc only)

Salmonella, Proteus, Morganella

Yersinia, Edwardsiella, Hafnia

38
Q

3 ways in which Pseudomonas can be distinguished from enterobacteriaceae species

A
  1. Pseudomonas is oxidase +
  2. Pseudomonas is a non-fermenter = red slant + red butt
  3. Pseudomonas grows blue-green, fruity-smelling colonies on BAP
39
Q

How can one tell a water supply has fecal contamination?

A

MacConkey plating of water will show E. coli

40
Q

One must distinguish ____ from ____ and ___ to determine fecal contamination of water because _____. How is this done?

A

E. coli from Klebsiella and Enterobacter

Klebsiella and Enterobacter can grow in water, so their presence doesn’t always mean fecal contamination

IMViC test

41
Q

What does IMViC stand for? What does each test test for?

A

Indole (conversion of tryptophan to indole)

Methyl red (production of acid from glucose)

Voges-Proskauer (conversion of glucose to acetylmethylcarbinol)

Citrate (utilization)

42
Q

Contents of MacConkey agar

A

Bile salts, lactose, pH indicator, crystal violet

43
Q

What is the purpose of the bile salts in MacConkey agar?

A

Kills off G+ bugs

44
Q

What is the purpose of the lactose and pH indicator in MacConkey agar?

A

Differentiates lac+ (red) from lac- (white) enterics

(i.e. E. coli from Shigella and Salmonella)

45
Q

Which organism could produce the result on the right?

A

Pseudomonas

46
Q

On special MacConkey agar medium, lactose can be replaced with ____ to help ID ____

A

Sorbitol

EHEC

(EHEC can’t ferment sorbitol like the rest of the E. coli so it would be white on sorbitol MacConkey agar)

47
Q

Which 3 enteric flora cause GI disease? Describe the disease(s) caused by each.

A
  1. C. perfringens - food-borne diarrhea, Abx-assc enterocolitis
  2. C. diff - Abx-assc pseudomembranous colitis, water diarrhea + vomiting
  3. C. botulinum - descending flaccid paralysis
48
Q

Why would you incubate feces in a microaerobic environment?

A

To grow Campylobacter

(Microaerobic = low O2 tension; H. pylori also grows in microaerobic environment)

49
Q

Why must urine be stored at 4 degrees before culture?

A

Prevent growth of bacteria and false +

50
Q

An EMB agar contains ___ and ___, which serve what function?

A

Eosin and methylene blue, which inhibit G+ bacteria

51
Q

Dx based on this EMB agar?

A

E. coli

(Green with metallic sheen due to acid precipitation of methylene blue by lac+ organisms)

52
Q

Dx based on this EMB agar?

A

Klebsiella

(Weakly fermentating bacteria show up as purple)

53
Q

Dx based on this EMB agar?

A

Salmonella

(Non-fermenters are white)

54
Q

Salmonella Shigella agar contains ____ which functions to ____.

A

High concetration of bile salts

Inhibits most coliforms (lac+ enterics) and all G+ bacteria so Shigella and Salmonella grow

55
Q

ID each bacteria grown on these Salmonella Shigella plates.

A

Top/white = Shigella (non-lactose fermenter)

Bottom left/black = Salmonella (H2S production)

Bottom right/red = E. coli (lactose fermenter; not inhibited by bile salts)

56
Q

We use Salmonella Shigella agar to differentiate between the lac - bacteria. However, we do not usually differentiate between the lac+ bacteria. Explain.

A

The only lac+ enteric that causes pathology is E. coli

Lac- enterics can grow to some degree in enteric media, so we have to distinguish Salmonella from Shigella

57
Q

____ will only show motility at the top of an agar because:

A

Pseudomonas

It’s a strict aerobe and this is where oxygen is plentiful

58
Q

Some species of ____ are only motile at room temp

A

Yersinia

59
Q

What is swarming? Which organisms do it?

A

High motility

Proteus and Morganella

60
Q

List two ways in which to differentiate Salmonella and Shigella

A

SS agar (Sal = black; Shig = white)

Serological testing (will also give you subgroup)

61
Q

Descending paralysis + bilateral facial nerve palsy

A

Botulism

GI (10 decks)

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