02 AST protocols Flashcards

1
Q

Performed on bacteria isolated from clinical specimens that are clinically significant

A

AST

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2
Q

T/F: S. pyogenes, S. agalactiae, N. meningitidis, L. monocytogenes are most frequently subject to AST

A

F (they are not subject to AST)

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3
Q

T/F: it is important in AST that the condition is not too acidic

A

T

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4
Q

Optimal pH for AST

A

7.2-7.4

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5
Q

Bacterial inoculum size of 0.5 McFarland Standard

A

1.5 x 10^8 CFU/mL

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6
Q

Colonies that are more than 1 day old are prone to false ___

A

susceptibility

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7
Q

Optimal concentration of Mg and Ca in AST

A

Ca: 25 mg/L
Mg: 12.5 mg/L

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8
Q

An increased cation concentration could lead to false resistance of ___ to ___

A

P. aeruginosa
Aminoglycoside

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9
Q

Incubation temperature when performing AST

A

35-37C

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10
Q

MRSA is incubated at ___

A

35C

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11
Q

Incubation period when performing AST

A

16-18 hrs

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12
Q

In performing AST, non-inhibitory medium such as ___, ___, ___ should be the source of 4-5 colonies

A

BAP
CAP
broth

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13
Q

Growth phase of the bacteria subject to AST after being transferred to a broth medium

A

log phase (3-5 hours)

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14
Q

Components of 0.5 McFarland Standard

A

99.5 mL 1% Sulfuric acid
0.5 mL 1.175% Barium chloride

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15
Q

0.5 McFarland standard is measured at ___ nm and should be at ___

A

625 nm
0.08-0.1

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16
Q

In performing AST, the standardized inoculum must be used within ___ mins

A

15

17
Q

The disk diffusion assay is reported as ___, ___, and ___

A

susceptible
resistant
intermediate

18
Q

The Kirby Bauer method is based on the ___ relationship between the zone of inhibition diameter

A

inverse linear