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Bacte LAB > AST > Flashcards

AST Flashcards

1
Q

ANTIBIOTICS
These chemical substances are produced by microorganisms with the capacity to inhibit (_____) or kill (______) other microorganisms.

A

bacteriostatic

bactericidal

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2
Q

T or F

Antibiotics

• They can also be synthesized via chemical procedures that are independent from microbial activity.

A

True

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3
Q

is an overall profile of antimicrobial susceptibility testing results of a specific microorganism to a battery of antimicrobial drugs.

A

antibiogram

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4
Q

CLASSIFICATION OF ANTIBACTERIAL DRUGS

A

Natural
Semi-synthetic
Synthetic

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5
Q

These drugs are produced by bacteria or fungi

A

NATURAL DRUGS

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6
Q

Natural drugs ex

A

Amphotericin B
Erythromycin
Kanamycin

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7
Q

These are modified natural drugs with added chemical groups

A

SEMI-SYNTHETIC DRUGS

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8
Q

Semi-synthetic ex

A

Ampicillin

Carbapenicillin

Methicillin

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9
Q

These are chemically produced drugs

A

SYNTHETIC DRUGS

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10
Q

Synthetic ex

A

Sulfonamides
Trimethoprim
Ciprofloxacin
Isoniazid

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11
Q

CLASSIFICATION OF ANTIMICROBIAL AGENTS

A

Bacteriostatic

Bactericidal

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12
Q

Ex:
Chloramphenicol
Dapsone
Sulfonamides
Erythromycin
Tetracycline

A

BACTERIOSTATIC AGENTS

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13
Q

• These are antimicrobial agents that inhibit bacterial growth; but generally, they do not kill the microorganisms.

A

BACTERIOSTATIC AGENTS

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14
Q

• Used as a treatment for life threatening conditions

Ex: Aminoglycosides (Gentamicin, Amikacin, and Streptomycin)

A

BACTERICIDAL AGENTS

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15
Q

These are antimicrobial agents that usually kill or destroy organisms

A

BACTERICIDAL AGENTS

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16
Q

Group A

A

Ampicillin, Gentamicin, Tobramycin, and Cefazolin

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17
Q

Group B

A

Amikacin, Cefuroxime, Ciprofloxacin, Impenem, and Piperacillin

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18
Q

Group C

A

Aztreonam, Chloramphenicol, and
Tetracycline

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19
Q

Lowest concentration of drug that inhibit bacterial growth

A

MINIMAL INHIBITORY CONCENTRATION (MIC)

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20
Q

• Ratio of the toxic dose to the therapeutic dose and as such, the higher the therapeutic index, the more effective the chemotherapeutic agent

A

THERAPEUTIC INDEX

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21
Q

TYPES OF ANTIMICROBIAL AGENTS ACCORDING TO MECHANISM OF ACTION

A

Cell wall inhibitors
Protein synthesis inhibitors
Nucleic acid synthesis inhibitors
Cell membrane inhibitors

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22
Q

These drug are effective against gram positive bacteria.

A

CELL WALL INHIBITORS

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23
Q

• They inhibit the activity of transpeptidase enzymes in which cell growth stops and the death of cells often follows.

A

CELL WALL INHIBITORS

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24
Q

• These are most selective antibiotics with a higher therapeutic index

A

CELL WALL INHIBITORS

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25
Q

Cell wall inhibitors

  • inhibits synthesis of peptidoglycan precursors
  • inhibits transpeptidation
  • can be bactericidal or bacteriostatic
  • inhibits translocation and elongation of peptidoglycan
A

Bacitracin

B-lactams

Isoniazid

Vancomycin

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26
Q

Effective against M. tuberculosis, B. fragilis, N. meningitidis, H. influenza, and S.pneumoniae.

A

PROTEIN SYNTHESIS INHIBITORS

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27
Q

• These drugs target aerobic and anaerobic gram (+) and gram (-) bacteria;

A

PROTEIN SYNTHESIS INHIBITORS

28
Q

These antibiotics bind to 30S subunit that results in the misreading of mRNA

A

PROTEIN SYNTHESIS INHIBITORS

29
Q

Translation
(50S subunit)
• Macrolides
• Streptogramins

Translation
(30S subunit)
• Aminoglycosides
• Tetracyclines

A

Protein synthesis inhibitors

30
Q

NUCLEIC ACID SYNTHESIS INHIBITORS

• - inhibits RNA polymerase and synthesis

• - effective for enteric bacteria (E. coli)

• - disrupts DNA and effective against anaerobic bacteria

A

Rifampicin

Quinolones

Metronidazole

31
Q

Nucleic acid synthesis inhibitors

A

Rifampicin

Quinolones

Metronidazole

32
Q

CELL WALL INHIBITORS

A

Bacitracin
B lactams
Isoniazid
Vancomycin

33
Q

Polymyxin B and E are effective against gram (-) bacteria, like PAE

A

CELL MEMBRANE INHIBITORS

34
Q

Folic Acid Inhibitors (Sulfamethoxazole)

Cord factor inhibitor (Isoniazid)

Take note that Trimethroprim and Sulfamethoxazole are synthetic drugs, they do not occur in nature.

A

ESSENTIAL METABOLITE INHIBITORS

35
Q

ACTIONS OF ANTIMICROBIAL DRUGS

A

Inhibits cell wall synthesis
Inhibits cell membrane function
Inhibits protein synthesis
Inhibits nucleic acid synthesis
Inhibitors of Other Metabolic Processes

36
Q

PRINCIPLE
• It measures the ability of an antibiotic or other microbial agent to inhibit bacterial growth

A

ANTIMICROBIAL SUSCEPTIBILITY TESTING

37
Q

PRIMARY GOAL
• To determine whether the bacterial isolate is capable of expressing resistance to the antimicrobial agents selected for treatment

A

ANTIMICROBIAL SUSCEPTIBILITY TESTING

38
Q

PURPOSE
To guide the clinician in selecting appropriate antimicrobial agent

To gather epidemiological data on microbial resistance

A

ANTIMICROBIAL SUSCEPTIBILITY TESTING

39
Q

STANDARDIZATION
• To optimize bacterial growth conditions
• To optimize conditions for maintaining antimicrobial integrity and activity
• To maintain reproducibility and consistency in the resistance profile

A

ANTIMICROBIAL SUSCEPTIBILITY TESTING

40
Q

DISK DIFFUSION METHOD (KIRBY-BAUER TEST)
• Medium:

A

Mueller-Hinton Agar

41
Q

• Standard:

A

0.5 McFarland/ Barium Sulfate Suspension

99.5ml of 1% sulfuric acid
0.5ml 1.175% barium chloride

42
Q

Standard inoculum:

A

1.5 x 10^8 CFU/ml

43
Q

pH:

A

7.2-7.4

44
Q

The standard susceptibility medium for non - fastidious bacteria.

A

MUELLER HINTON AGAR

45
Q

MUELLER HINTON AGAR

Components

A

beef infusion
agar
nucleic acid
vitamins
casein

46
Q

• An MH broth with_____ is used to improve the detection of oxacillin - resistant staphylococci.

A

2% NaCl

47
Q

• An MH broth with ________is utilized for testing susceptibility for streptococci, N. meningitidis, and other fastidious organisms.

A

5% lysed horse blood or sheep blood

48
Q

MHA

• Depth:
• Condition:
• Temperature:
• Incubation Time:
• Antibiotic disc:
• Petroff-Hausser:

A

4mm

Aerobic, No CO2

35-37°C

16-18 hours

6mm

bacterial count

49
Q

• A calibrated chamber with a grid etched on its surface.

• Designed for accurate measurement of cell concentration in a given volume of liquid.

A

Petroff-Hausser Counting Chamber

50
Q

FACTORS AFFECTING DISK DIFFUSION

A

Amount of inoculum
Thickness of susceptibility plate
Growth rate of organism
pH of medium
Number of disk per plate
Concentration of divalent bonds

51
Q

If the agar is too thick, the zone sizes will be_____;

if the agar is too thin, the zone sizes will be_____

A

smaller

larger

52
Q

•A temperature of_____ is best for most bacteria within______ of incubation

Temperatures higher than 35 degrees may lead to false detection of______

Lower temperature may lead to_____ ZOl Incubation with increased 5% to 10% carbon dioxide is not recommended except for capnophilic bacteria.

A

35 degrees; 16 - 18 hours

MRSA

larger

53
Q

• Incubation of plates in CO2 could result in_______ pH.

• Increased pH (alk) results to_____ activity of tetracycline drugs.

• Low pH (acidic)______ the activity of aminoglycosides and erythromycin.

A

decreased (ACIDIC)

decreased

decreases

54
Q

A 150mm plate can have a maximum of____ disks.

Placement of more than that may result in….

A

12

overlapping of zones

55
Q

PROCEDURE AST
I. Pure inocula are obtained by selecting_____ colonies of the same morphology

  1. Colonies are suspended into____ to achieve a turbid suspension.
  2. Bacterial suspension &_____ solution are compared by matching the turbidity if the tubes against a____ background.
  3. Turn the plate____ between each streaking (Overlapping
    Streaking)
  4. Within____. of inoculation, antimicrobial agents are applied onto MHA.
  5. Within_____. of disk placement, plates are inverted & incubated at
    35C for 16-18hrs.
  6. Diameter of each inhibition zone is measured using a caliper or ruler.
A

4-5

0.85% NSS

McFarland; dark

60 degrees

15mins

15mins

56
Q

MEASUREMENTS
= Disk distance
= 12 discs
= 5-6 discs

A

15mm

150mm

100mm

57
Q

MEASUREMENTS
15mm = Disk distance
150mm =
100mm =

A

12 discs

5-6 discs

58
Q

FALSE RESISTANT

A

15 mins (delay of disc application)

Increase moisture

Thick medium

Increase organisms = Decrease Zone of
Inhibition

59
Q

FALSE SENSITIVE

A

15 mins (delay of incubation)

Increase drying

Thin medium

Decrease organisms = Increase Zone of
Inhibition

60
Q

•: microorganism should respond to therapy with that antimicrobial agent

•: microorganism falls into a range of susceptibility in which the MIC approaches or exceed the level of antimicrobial agent that can be achieved and for which clinical response is likely to be less than with a suspetible strain

: no zone or small zone of inhibition - antibiotic is not the appropriate choice for treatment

A

Susceptible

Intermediate

Resistant

61
Q

It is fully automated equipment designed for the identification of bacteria and AST

Optical readings are made every 15 minutes to measure transmitted light through each well

Final reading 6-8 hours

A

Vitek 2

62
Q

Inocula are manually introduced to the broth microdilution tray

Growth patterns are automatically read and interpreted after incubation.

A

Microscan Walkaway System by Beckman Coulter

63
Q

It uses manual gravity based inoculation technique.

Growth patterns are automatically read.
It has a mechanism to confirm ESBL of gram negative bacteria.

Results after 8 to 12 hours.

A

Phoenix System by BD Microbiology Systems

64
Q

infection is caused by a strain of Staphylococcus bacteria that’s become resistant to oxacillin and methicillin

A

MRSA

65
Q

2 TYPES OF MRSA

A

• Health care-associated MRSA (HA-MRSA)

• Community - associated MRSA (CA-MRSA)

66
Q

Are associated with invasive procedures or devices, such as surgeries, intravenous tubing or artificial joints

A

Health care-associated MRSA (HA-MRSA)

67
Q

Often begins as a painful skin boil. Spread by skin- to-skin contact.

At risk populations include groups such as high school wrestlers, child care workers and people who live in crowded conditions.

A

Community - associated MRSA (CA-MRSA)

Bacte LAB (38 decks)

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