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Clinical Bacteriology > LAB S18 > Flashcards

LAB S18 Flashcards

(61 cards)

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1
Q

determine the susceptibility of microorganisms to one or several antimicrobial agents

A

Antimicrobial Susceptability Test

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2
Q

act against microorganisms by blocking essential cellular processes

A

antimicrobial agents

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3
Q

Antimicrobial agents block essential cellular processes which are: (4)

A

> cell wall synthesis
protein synthesis
DNA replication/ transcription
cellular respiration

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4
Q

the property of being able to inhibit microbial growth

A

microbiostatic

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5
Q

the property of being able to kill microbes

A

microbicidal

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6
Q

pharmaceutical agents that include antibiotics (antibacterials), antifungal, antiviral , and antiparasitic drugs

A

antimicrobial drugs

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7
Q

susceptibility profile of a microorganism

A

antibiogram

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8
Q

lowest concentration of an antibiotic that inhibits visible growth of a microorganism in an in vitro system

A

Minimum Inhibitory Concentration (MIC)

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9
Q

Three major uses of AST

A
  1. As a chemotherapeutic guide
  2. As an epidemiological surveillance tool
  3. As a laboratory diagnostic tool
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10
Q

AST is used when susceptibility of bacteria cannot be predicted from its identity. However, it is not needed if the susceptibility profile is predicatable.

Streptococcus pyogenes is predictably susceptible to:

A

penicillin

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11
Q

Anaerobes are predictably susceptible to:

A

metronidazole

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12
Q

Klebsiella pneumoniae is predictably resistant to:

A

ampicillin

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13
Q

Proteus species is predictably resistant to:

A

nitrofurantonin and tetracyclines

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14
Q

Susceptibility:

Streptococcus pyogenes

A

penicillin

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15
Q

Suscpetibility:

Anaerobes

A

metronidazole

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16
Q

Resistance:

Klebsiella pneumonae

A

ampicillin

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17
Q

Resistance:

Proteus species

A

nitrofurantoin and tetracyclines

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18
Q

property of antimicrobial drugs wherein it acts within the host without damaging the host

A

selective toxicity

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19
Q

Three purposes of AST as an epidemiological surveillance tool

A

Aid in

  1. monitoring susceptibility patterns in a region or hospital
  2. appropriate empiric antibiotic therapy (giving amoxicillin for community acquired pneumonia)
  3. monitoring emergence of acquired resistance
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20
Q

Five most common bacterial pathogens for communith-acquired pneumonia (CAP)

A
  1. Streptococcus pneumoniae
  2. Haemophilus influenzae
  3. Chlamydophila pneumoniae
  4. Mycoplasma pneumoniae
  5. Moraxella catarrahlis
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21
Q

Most community acquired pneumonia bacterial pathogens are susceptible to:

A

amoxicillin

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22
Q

Streptococcus bacteria can be identified in laboratpry diagnosis through its susceptibility to:

A

Bacitracin

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23
Q

Bacitracin inhibits what groups of Streptococcus bacteria:

A

99% group A (S. pyogenes)
small percentage of group B
10-20% of group C and G

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24
Q

used routinely for testing common, rapidly growing, and certain fastidious bacterial pathogens

A

Kirby-Bauer Agar Disk Diffusion method

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25
Principle of Kirby Bauer Agar Disk Diffusion Method
Diffusion | movement of molecules from area of high to low concentration
26
Mode of Action of Kirby Bauer Agard Disk Diffusion Method
a. Impregnated disk of antimicrobial agent comes in contact with the moist agar surface b. water is absorbed into the filter paper  c. antimicrobial agents diffuse into the surrounding medium
27
The concentration of diffused antimicrobial agent at the interface of growing and inhibited bacteria, approximates the MIC
Critical Concentration
28
Standards for agar disk diffusion method used to determine the in vitro antimicrobial susceptibility of bacteria that grow aerobically and can be modified for fastidious bacteria
CLSI M02
29
Standards for antimicrobial susceptibility of bacteria that grow aerobically using dilution methods
CLSI M07
30
Standards for antimicrobial susceptibility of bacteria that grow anaerobically
CLSI M11
31
contains tables that represent the most current information for drug selection, interpretation, and quality control
CLSI M100
32
Broth used in Kirby Bauer Inoculum
Trypticase Soy Broth (TSB)
33
Turbidity of onoculum is compared ro
0.5 Mcfarland Standard
34
Agar used in Kirby Bauer method
Mueller- Hinton Agar
35
Inoculum variables that affect the test
1. purity 2. age (should be in log phase) 3. density (0.5 Mcfarland Standard)
36
Two types of Inoculum preparation
1. Broth culture method (TSB incubated 2-6 hours) | 2. Colony suspension method (direct suspension of 18-24 hrs old colony)
37
Inoculum preparation method used for non fastidious bacteria (except staphyllococci)
broth culture method
38
Inoculum preperation method used for fastidious bacteria
Colony suspension method
39
Effect on ZOI: | Lighter turbidity of inoculum
larger ZOI
40
Effect on ZOI: | Denser or more turbid inoculum
smaller ZOI
41
4 test medium variables that affect the test:
1. Type (should be MHA) 2. pH 3. Depth 4. Moisture
42
Most recommended Test medium type
Mueller- Hinton Agar (MHA)
43
Physiologic concentration of divalent magnesium
20-35 mg/L
44
physiologic concentration of divalent calcium
50-100 mg/L
45
CFU/ml of Mcfarland compared inoculum
1-2 × 10^8
46
Effect on ZOI: | less cation
larger ZOI
47
Effect on ZOI: | more cation in test medium
smaller ZOI
48
Effect on ZOI: | high thymidine
smaller ZOI
49
recommended pH of test medium
7.2 to 7.4
50
Effect on ZOI: | low pH of test medium on aminoglycosides and macrolides like erythromycin
smaller ZOI
51
Effect on ZOI: | low pH of test medium for tetracyclines
larger ZOI
52
Effect on ZOI: | high pH of test medium for aminoglycosides and macrolides like erythromycin
large ZOI
53
Effect on ZOI: | high pH of test medium of tetracyclines
smaller ZOI
54
recommended depth of test medium
4mm
55
recommended mL for 100 mm plate
25-30 mL
56
recommended mL for 150 mm plate
60-70 mL
57
Effect on ZOI: | too shallow test medium
larger ZOI
58
Effect on ZOI: | too deep test medium
smaller ZOI
59
effect on ZOI | too dry test medium
smaller ZOI
60
effect on ZOI | too moist test medium
larger ZOI
61
diameter of antimicrobial disk
6mm

Clinical Bacteriology (12 decks)

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