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[1L] IDENTIFICATION TESTS > Streptococcus species > Flashcards

Streptococcus species Flashcards

1
Q

Prepared media

A
  1. Blood agar plate (sheep BAM)
  2. sodium hippurate broth
  3. Todd-Hewitt broth (or trypticase soy broth)
  4. bile-esculin agar
  5. 6.5% NaCl broth
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2
Q

Reagents

A
  1. 3% hydrogen peroxide
  2. ferric chloride reagent
  3. ninhydrin reagent
  4. 2% sodium desoxycholate
  5. 10% sodium desoxycholate
  6. phenol red indicator
  7. 0.10N NaOH
  8. β-hemolysin-producing S. aureus
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3
Q

Antimicrobial discs

A
  1. bacitracin
  2. 0.04 U (Taxo “A”)
  3. SXT (trimethoprim,-sulfamethoxazole, 1.25 µg/23.75 µg)
  4. Optochin
  5. 5 µg (Taxo “P”)
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4
Q

Streptococcus and streptococcal-like bacterial groups

A

gram-positive cocci and catalase-negative

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5
Q

The idenCficaCon tests to be performed are determined by the type of

A

hemolysis on BAM

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6
Q

Beta-type inoculations

A

a. Bacitracin and SXT (Trimethoprim-Sulfamethoxazole) susceptibility tests
b. CAMP test
c. Sodium hippurate hydrolysis test

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7
Q

Alpha-type inoculations

A

a. Optochin susceptibility test
b. Bile solubility test
c. Bile-esculin hydrolysis test
d. Salt tolerance test

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8
Q

a. Bacitracin and SXT (Trimethoprim-Sulfamethoxazole) susceptibility tests

Positive result [susceptible (S)]

A

Any zone of inhibition around the disc

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9
Q

a. Bacitracin and SXT (Trimethoprim-Sulfamethoxazole) susceptibility tests

Negative result [resistant (R)]

A

No zone of inhibition

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10
Q

Bacitracin (S), SXT (R)

A

Group A streptococcus

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11
Q

Bacitracin (R), SXT (R)

A

Group B streptococcus

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12
Q

Bacitracin (S or R), SXT (S)

A

β-hemolytic streptococcus, Groups C, F, or G

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13
Q

b. CAMP test: Positive result

A

Arrowhead-shaped zone of β-hemolysis at the juncture of the two organisms

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14
Q

b. CAMP test: Negative result

A

No arrowhead-shaped zone of β-hemolysis

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15
Q

b. CAMP test: Positive control

A

Group B streptococcus

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16
Q

b. CAMP test: Negative control

A

Group A streptococcus

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17
Q

c. Sodium hippurate hydrolysis test:

Benzoate test:

A

0.2 ml of ferric chloride reagent

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18
Q

c. Sodium hippurate hydrolysis test:

Glycine test:

A

0.2 ml ninhydrin reagent

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19
Q

c. Sodium hippurate hydrolysis test:

Benzoate test: Positive result

A

Heavy precipitation that persists for 10 minutes or longer

20
Q

c. Sodium hippurate hydrolysis test:

Glycine test: Positive result

A

Deep blue or purple color

21
Q

c. Sodium hippurate hydrolysis test:

Benzoate test: Negative result

A

Precipitation that clears within 10 minutes

22
Q

c. Sodium hippurate hydrolysis test:

Glycine test: Negative result

A

Colorless or slightly yellow-pink color

23
Q

c. Sodium hippurate hydrolysis test:

Positive control

A

Group B streptococcus

24
Q

c. Sodium hippurate hydrolysis test:

Negative control

A

Group A streptococcus

25
Q

a. Optochin susceptibility test: Positive result (optochin-susceptible)

A

A zone of inhibition of >14 mm with 6-mm disc (>16 mm with 10-mm disc)

26
Q

a. Optochin susceptibility test: Negative result (optochin-resistant)

A

No zone of inhibition or a zone of inhibition <14 mm (or <16 mm)

27
Q

a. Optochin susceptibility test:

Optochin (S)

A

Streptococcus pneumoniae

28
Q

a. Optochin susceptibility test:

Optochin (R)

A

Viridans streptococcus

Enterococcus faecalis

29
Q

b. Bile solubility test: Plate test

Positive result (bile-soluble)

A

Disappearance of colonies on which the reagent was placed; an imprint of the lyzed colonies may remain within the zone

30
Q

b. Bile solubility test: Plate test

Negative result (bile-insoluble)

A

Colonies where the reagent was placed remains intact and visible

31
Q

b. Bile solubility test: Broth test

Positive result (bile-soluble)

A

Visible clearing of the “test” suspension, with no clearing in the “control” suspension

32
Q

b. Bile solubility test: Broth test

Negative result (bile-insoluble)

A

No change in the turbidity of the “test” suspension relative to the “control” suspension

33
Q

b. Bile solubility test:

Positive control

A

Streptococcus pneumoniae

34
Q

b. Bile solubility test:

Negative control

A

Viridans streptococcus

35
Q

b. Bile solubility test: Reagent

A

1 drop of phenol red indicator
0.10N NaOH until indicator becomes light
pink in color

36
Q

b. Bile solubility test: Reagent

reagent to be added in the tube labeled
“test
‘

A

0.5 ml of 10% sodium desoxycholate

37
Q

b. Bile solubility test: Reagent

reagent to be added in the tube labeled
“control”

A

0.5 ml of sterile NSS

38
Q

c. Bile-esculin hydrolysis test:

Positive result

A

Blackening of the medium

39
Q

c. Bile-esculin hydrolysis test:

Negative result

A

No blackening of the medium

40
Q

c. Bile-esculin hydrolysis test:

Positive control

A

Enterococcus species

41
Q

c. Bile-esculin hydrolysis test:

Negative control

A

Viridans streptococcus, not group D

42
Q

d. Salt tolerance test: Positive result

A

Visible turbidity in broth with or without color change from purple to yellow

43
Q

d. Salt tolerance test: Negative result

A

No turbidity and no color change

44
Q

d. Salt tolerance test: Positive control

A

Enterococcus faecalis

45
Q

d. Salt tolerance test: Negative control

A

Streptococcus bovis

[1L] IDENTIFICATION TESTS (8 decks)

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