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Clinical Bacteriology > LAB S20 > Flashcards

LAB S20 Flashcards

1
Q

hemolysis and Lancefield classification of S. pyogenes

A

group A beta hemolytic

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2
Q

hemolysis and lancefield classification of S. agalactiae

A

group B beta hemolytic

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3
Q

hemolysis of S. pyogenes

A

alpha hemolytic

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4
Q

morphology of streptococcus and enterococcus in microscope

A

G+ cocci in chains

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5
Q

morphology of S. pneumoniae in microscope

A

cocci in pairs
slightly elongated lanceolate
surrounded by halo (polysaccharide capsule)

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6
Q

three culture media used for streptococci species

A

5% sheep BAM
Columbia CNA agar
PEA agar

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7
Q

inoculation technique for streptococcus

A

streak stab technique

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8
Q

purpose of streak swab technique in streptococcus inoculation

A

creates a relatuvely anaerobic environment

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9
Q

streptococcal growth is enhanced by

A

5-10% CO2

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10
Q

most streptococci will grow on agar media at incubation of:

A

35-37 C within 48 hours

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11
Q

About 0.5 mm in diameter, grayish white, convex, entire, transparent to translucent, matte or glossy; large zone of β-hemolysis, 2x-4x the diameter of the colony.

A

Group A

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12
Q

Larger than group A streptococci; translucent to opaque; flat, glossy;
narrow zone of β-hemolysis

A

Group B

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13
Q

Grayish white, glistening; wide zone of β-hemolysis

A

Group C

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14
Q

Grayish white, small, matte; narrow to wide zone of β-hemolysis

A

Group F

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15
Q

Grayish white, matte; wide zone of β-hemolysis

A

Group G

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16
Q

Small, gray, glistening

young are dome-shaped, later umbilicated

A

S. pneumoniae

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17
Q

Minute to small, gray, domed, smooth or matte; α- or ɣ-hemolysis

A

Viridans streptococci

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18
Q

Small, cream or white, smooth, entire; α–, β-, or ɣ-hemolysis

A

Enterococcus spp.

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19
Q

oxygen labile hemolysin

A

streptolysin O

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20
Q

oxygen stable hemolysis

A

streptolysin S

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21
Q

causes beta hemolysis in the surface of agar

A

streptolysin S

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22
Q

causes beta hemolysis im the subsurface of the agar

A

streptolysin O

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23
Q

results in the greening of agar

A

alpha hemolysis

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24
Q

alpha hemolytic streptococci

A

S. lneumoniase, viridans group, Enterococcus

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25
Q

hemolysis of Entterococcus species cultivated 24 hours in aerobic atmosphere at 37C

A

gamma hemolysis

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26
Q

other gamma hemolytic species

A 
group D streptococci
viridans group (sometimes)
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27
Q

two characteristics for presumptive identification of S. pneumoniae

A

a-hemolytic dome shaped mucoiddue to large amounts of capsular polysaccharide

checker-piece/ nail head colonies due to organism autolysis

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28
Q

4 tests for identification of Beta hemolytic streptococci

A

Bacitracin (Taxo A) test
SXT (trimethoprim-sulfamethoxazole) test
CAMP test
sodium hippurate hydrolysis test

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29
Q

Used for presumptive identification of group A β-hemolytic streptococci

A

bacitracin (taxo A) test

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30
Q

concentration of bacitracin in taxo A test

A

0.04 u

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31
Q

Used for presumptive identification of groups C, F, or G β-hemolytic streptococci

A

SXT (trimethoprim- sulfamethoxazole test)

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32
Q

concentration of trimethoprim in SXT test

A

1.25 g

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33
Q

concentration of sulfamethoxazole in SXT test

A

23.75 ug

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34
Q

bacitracin susceptible, SXT resistant

A

group A

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35
Q

bacitracin resistant, SXT resistant

A

group B

36
Q

bacitracin resistant or susceptible, SXT susceptible

A

Group C, F, G

37
Q

CAMP test meaning

A

Christie, Atkins, Munch- Petersen (1944)

38
Q

Used for presumptive identification of bacitracin-resistant Group B β-hemolytic streptococci

A

CAMP test

39
Q

extracellular substance enhancing hemolytic activity of S. aureus

A

CAMP factor

40
Q

when group B streptococci enhances hemolytic effect of S. aureus, it is termed as

A

synergistic hemolysis

41
Q

synergistic hemolysis is observed as

A

arrow head shaped zone where the two organisms intersect

42
Q

positive camp test (arrow head zone) is characteristic of

A

Group B B-hemolytic streptococcus

43
Q

CAMP negative

A

Group A streptococcus

44
Q

also used for presumptive identification of bacitracin-resistant Group B β-hemolytic streptococci

A

sodium hippurate hydrolysis test

45
Q

Group B streptococcus hydrolyzes hipourate into:

A

benzoate and glycine

46
Q

mixed with benzoic acid for precipitation to determine hippurate hydrolysis

A

ferric chloride

47
Q

how to determine positive benzoic acid test

A

wait for precipitate to persist for 10 minutes

48
Q

mixed with glycine to determine hippurate hydrolysis

A

ninhydrin

49
Q

ninhydrin mechanism of action on glycine

A

deaminate alpha amink compounds which releases ammonia and carbon dioxide, forming a purple or deep blue color

50
Q

positive result for sodium hippurate hydrolysis

A

10 mins precipitate for benzoic acid

deep blue or purple color for glycine

51
Q

hippurate positive streptococcus

A

Group B

52
Q

hippurate negative streptococcus

A

Group A

53
Q

2 tests for identification of alpha hemolytic streptococci

A

Optochin Taxo P susceptibility test

Bile solubility test

54
Q

other name for optochin

A

ethylhydrocuprein hydrochloride

55
Q

principle of optochin susceptibility

A

inhibits growth of S. pneumoniae

56
Q

more than 14 mm ZOI for optochin

A

S. pneumoniae

57
Q

less than 14 mm ZOI for optochin

A

viridans or group D

58
Q

S. pneumoniae produces an autolytic intracellular amidase enzyme known as

A

desoxycholate

59
Q

desoxycholate is activated by

A

bile

60
Q

In bile solubility test, S. pneumoniae undergoes:

A

rapid autolysis

61
Q

bile solubility test positive result

A

disappearance of colonies = S. pneumoniae

62
Q

bile solubility negative result

A

intact colonies = viridans and group D

63
Q

Three other methods to distinguish between S. pneumoniae and viridans group

A
  1. Quellung or Neufeld reaction
  2. inulin fermentation test
  3. mouse virulence test
64
Q

principle of Quellung reaction

A

anticapsular antibodies react with polysaccharide capsule of S. pneumoniae

65
Q

Positive quellung reaction:

A

clumping, halo effect, light blue outline = S. pneumoniae

66
Q

negative quellung reaction:

A

viridans streptococci

67
Q

principle of inulin fermentation test

A

S. pneumoniae can ferment inulin with acid and gas

68
Q

positive inulin fermentation test

A

S. pneumoniae

69
Q

negative inulin fermentation

A

viridans group

70
Q

based on sensitivity of white mouse to S. pneumoniae

A

mouse virulence test

71
Q

inoculation method of white mouse

A

intraperitoneal injection

72
Q

positive mouse virulence test

A

death of mouse within 1-2 days = S. pneumoniae

73
Q

Tests for identification of Group D streptococci and Enterococcus species

A
  1. Bile esculin test

2. Salt tolerance test

74
Q

principle of bile-esculin test

A

ability of Group D and Enterococcus species to grow in 40% bile
hydrolyze esculin into glucose and esculetin
esculetin reacts with ferric ions (from ferric citrate)
results into black diffusible complex

75
Q

bile esculin test positive result:

A

blackening of medium: Group D/ Enterococcus

76
Q

bile esculin test

A

no blackening = viridans

77
Q

salt tolerance test principle

A

ability of enterococcus to grow in the presence of 6.5% NaCl

78
Q

positive result of salt tolerance

A

visible turbidity/ change of color from purple to yellow = enterococcus

79
Q

negative result of salt tolerance

A

no turbidity and color change = Group D

80
Q

Other methods to distinguish between Group D and enterococcus

A
  1. pyrrolidonyl arylamidase (PYR) test

2. susceptibility to penicillin

81
Q

principle of pyrrolidonyl arylamidase test

A

pyrrolidonyl arylamidase hydrolyzes PYR, which releases free B-naphthylamid + addition of diazo dye coupler forming a red Schiff base

82
Q

PYR positive

A

Enterococcus

83
Q

PYR negative

A

Group D streptococci

84
Q

penicillin resistant

A

Enterococcus

85
Q

penicillin susceptible

A

Group D

Clinical Bacteriology (12 decks)

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