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Bacteriology (LAB) > Antimicrobial Suceptibility Testing > Flashcards

Antimicrobial Suceptibility Testing Flashcards

1
Q

These are compounds that kill or inhibit microorganisms.

A

Antimicrobials

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2
Q

These are antimicrobials, usually of low molecular weight, produced by microorganisms that inhibit or kill other microorganisms.

A

Antibiotics

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3
Q

It is performed on bacterial and fungal isolates to determine which antimicrobial agents might be effective in treating infections caused by these organisms.

A

Antibiotic Susceptibility Testing

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4
Q

What is the primary goal of AST?

A

To determine whether the bacterial isolate is capable of expressing resistance to the antimicrobial agents selectied for treatment.

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5
Q

Which method/s are used for AST?

A

Diffusion and Dilution

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6
Q

The methods for AST are done to determine the _____.

A

Minimal Inhibitory Concentration (MIC)

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7
Q

It is the lowest antimicrobial concentration that completely inhibits visible bacterial growth.

A

Minimal Inhibitory Concentration (MIC)

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8
Q

What is Minimal Inhibitory Concentration (MIC)?

A

It is the lowest antimicrobial concentration that completely inhibits visible bacterial growth.

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9
Q

Standards that describe the methods for AST are published and frequently updated by the _________.

A

Clincal and Laboratory Standards Institute (CLSI)

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10
Q

CLSI is formerly known as _____.

A

National Committee for Clinical Laboratory Standards (NCCLS)

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11
Q

Standardized components of AST

A
  • Bacterial inoculum size
  • Growth medium
  • Incubation atmosphere
  • Incubation temperature
  • Incubation duration
  • Antimicrobial concentrations
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12
Q

Bacterial Inoculum size for Disk Diffusion

A

1.5 x 10^8 CFU/mL

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13
Q

Bacterial Inoculum size for Broth Microdilution

A

5 x 10^5 CFU/mL

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14
Q

Standard growth medium for AST

A

Mueller-Hinton Base

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15
Q

Growth medium components for AST

A
  • pH
  • Cation concentration
  • Blood and serum supplements
  • Thymidine content
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16
Q

Standard pH of growth medium for AST

A

7.2 - 7.4

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17
Q

Standard cation concentration of growth medium for AST

A
  • Ca: 25 mg/L
  • Mg: 12.5 mg/L
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18
Q

Incubation atmosphere for AST

A

Ambient air

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19
Q

Incubation temperature for AST

A

35 C

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20
Q

Incubation duration for AST (Disk Diffusion)

A

16 - 18 hours

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21
Q

Incubation duration for AST (Broth Microdilution)

A

16 - 20 hours

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22
Q

Antimicrobial concentrations for AST

A

Based on CLSI, but the goal is to get the lowest concentration

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23
Q

Agar depth for AST (Disk Diffusion)

A

3 - 5 mm

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24
Q

Factors to consider when determining whether testing is warranted

A
  • Body site from which the bacterium was isolated
  • Presence of other organisms and quality of the specimen
  • Host’s status
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25
Q

Long term storage of ATB discs

A

-20 C or below in a non-frost-free freezer

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26
Q

A working supply of disks can be stored in a refrigerator at ______ for at least 1 week.

A

2 - 8 C

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27
Q

A working supply of disks can be stored in a refrigerator at 2-8 C for at least _____.

A

1 week

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28
Q

Disks should always be stored in a tightly sealed container with ______.

A

desiccant

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29
Q

The container should be allowed to warm to room temperature before opening to prevent _______.

A

condensation

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30
Q

The container should be allowed to warm to ________ before opening to prevent condensation.

A

room temperature

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31
Q

Which tool is used to obtain ATBs from the ampule?

A

Forceps

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32
Q

Desiccant is used to ______.

A

prevent moisture

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33
Q

It is one of the most critical steps in susceptibility testing.

A

Inoculum preparation

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34
Q

Inoculum Preparation

Prepared by adding cells from ____ of similar colony morphology.

A

four to five isolated colonies

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35
Q

Inoculum Preparation

Isolated colonies added are allowed to grow to the ____ phase.

A

log

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36
Q

This result is obtained when too few bacteria are tested.

A

False-susceptible

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37
Q

This result is obtained when too many bacteria are tested.

A

False-resistant

38
Q

The ____ of the inoculum is compared to the McFarland Standard.

A

turbidity

39
Q

Components of McFarland Turbidity Standard

A
  • 99.5 mL of 1% sulfuric acid
  • 0.5 mL of 1.175% barium chloride
40
Q

If the inoculum is not turbid enough to meet the McFarland Standard, what should be done?

A

Add more organism

41
Q

If the inoculum is too turbid to meet the McFarland Standard, what should be done?

A

Dilute by adding more broth

42
Q

Methods of Diffusion in AST

A
  • Kirby-Bauer Diffusion Method
  • Agar Cup Diffusion Method
  • Agar Cylinder Diffusion Method
  • Epsilometer or Gradient Diffusion Method
43
Q

Methods of Dilution in AST

A
  • Macrobroth Method or Tube Dilution Method
  • Microtube Dilution Method
44
Q

Volume of broth in Macrobroth Method

A

1 mL or greater

45
Q

Volume of broth in Microtube Dilution Method

A

0.05 mL to 0.1 mL

46
Q

The most common method of Diffusion

A

Kirby-Bauer Diffusion Method

47
Q

Kirby-Bauer Diffusion Method is also known as _______.

A
  • Agar Diffusion Method
  • Disk Diffusion Method
48
Q

Step-by-Step Procedure for AST

A
  1. Preparation of pure inoculum
  2. Standardize pure inoculum
  3. Streak the pure inoculum
  4. Appy antibiotic discs
  5. Incubate
  6. Measure ZOI
49
Q

Which media can be used for AST?

A
  • Mueller-Hinton Broth
  • Trypticase Soy Agar
  • Sterilized Distilled Water
  • Natural Saline Solution
  • Brain Heart Infusion Broth
50
Q

Which tool is used to streak the pure inoculum into the medium for AST?

A

Sterile cotton swab

51
Q

What motion/pattern is used in streaking the pure inoculum on the agar in AST?

A

Zigzag

52
Q

The spaces between each antibiotic must be ____ away from each other.

A

15 mm

53
Q

Instrument/s used for measuring ZOI

A
  • Ruler
  • Microcaliper
  • Vernier caliper
54
Q

Unit of measurement for measuring ZOI

A

mm

55
Q

Identify the test being described.

It measures the amount of antimicrobial agent in serum or body fluid.

A

Antimicrobial Concentration Test (Assay)

56
Q

Identify the test being described.

It measures the lowest concentration of antimicrobial agent that kills a bacterial isolate.

A

Minimum Bactericidal Concentration Test

57
Q

Identify the test being described.

It measures the highest dilution or titer of a patient’s serum that is inhibitory to the patient’s own infecting bacterium and highest dilution or titer that is bactericidal.

A

Serum Bactericidal Test

58
Q

Identify the test being described.

It measures the susceptibility of a bacterial isolate to a combination of two or more antimicrobial agents.

A

Synergy Test

59
Q

Identify the test being described.

It measures the rate of killing of bacteria by an antimicrobial agent.

A

Time-kill Assay

60
Q

Antibiotics affecting gram (+) organisms only

A
  • Vancomycin
  • Bacitracin
61
Q

Antibiotics affecting Mycobacterium tuberculosis

A

Isoniazid

62
Q

Antibiotics affecting gram (+) and (-) organisms

A
  • Penicillin
  • Fluoroquinolones
  • Rifamycins
  • Tetracyclines
  • Streptomycin
  • Chloramphenicol
  • Sulfa drugs
63
Q

ATBs targeting the cell wall

A
  • Penicillin
  • Vancomycin
  • Bacitracin
  • Isoniazid
64
Q

ATBs targeting the DNA

A

Fluoroquinolones

65
Q

ATBs targeting the RNA

A

Rifamycin

66
Q

ATBs targeting protein synthesis

A
  • Tetracyclines
  • Streptomycin
  • Chloramphenicol
67
Q

Abbreviate the ATB

Penicillin

A

PCN

68
Q

Abbreviate the ATB

Vancomycin

A

VAN

69
Q

Abbreviate the ATB

Bacitracin

A

BAC

70
Q

Abbreviate the ATB

Isoniazid

A

INH

71
Q

Abbreviate the ATB

Fluoroquinolones

A

FQ

72
Q

Abbreviate the ATB

Rifamycins

A

RIF

73
Q

Abbreviate the ATB

Tetracyclines

A

TET

74
Q

Abbreviate the ATB

Streptomycin

A

STR

75
Q

Abbreviate the ATB

Chloramphenicol

A

CHL

76
Q

Abbreviate the ATB

Meropenem

A

MPM

77
Q

Abbreviate the ATB

Imipenem

A

IPM

78
Q

Abbreviate the ATB

Levofloxacin

A

LEV

79
Q

Abbreviate the ATB

Ciprofloxacin

A

CIP

80
Q

Abbreviate the ATB

Erythromycin

A

ERY

81
Q

Abbreviate the ATB

Amoxicillin

A

AMX

82
Q

Abbreviate the ATB

Gentamycin

A

GEN

83
Q

Abbreviate the ATB

Aztreonam

A

ATM

84
Q

Abbreviate the ATB

Ceftriaxone

A

CRO

85
Q

Abbreviate the ATB

Polymixin B

A

PB

86
Q

Abbreviate the ATB

Azithromycin

A

AZM

87
Q

Concentration of Meropenem

A

10 ug

88
Q

Concentration of Imipenem

A

10 ug

89
Q

Concentration of Levofloxacin

A

5 ug

90
Q

Concentration of Ciprofloxacin

A

5 ug

91
Q

Concentration of Erythromycin

A

15 ug

92
Q

Concentration of Amoxicillin

A

30 ug

Bacteriology (LAB) (3 decks)

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