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CSMLS > MICRO Quality Control/ Antibiotics > Flashcards

MICRO Quality Control/ Antibiotics Flashcards

1
Q

Describe 5 mechanisms of action for common antibiotics

A
  1. Beta-lactam inhibits transpeptidation (CELL WALL SYNTHESIS)
  2. Targeted ribosomal subunits = inhibits PROTEIN SYNTHESIS
  3. Drugs bind enzymes responsible for DNA/RNA SYNTHESIS
  4. Sulfa- trimeth- inhibits folic acid METABOLIC PATHWAY
  5. Polymixins = detergents disrupt CELL MEMBRANE INTEGRITY
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2
Q

Antimicrobial groups that inhibit cell wall synthesis (3)

A
  • Glycopeptides
  • Beta lactams
  • Cephalosporins
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3
Q

Antimicrobial groups that inhibit protein synthesis (6)

A
  • Aminoglyocsides
  • Tetracycline
  • MLSO (Macrolides, Lincosamides, Streptogramins, Oxazolidinones)
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4
Q

List antimicrobial groups that inhibit DNA/RNA synthesis (2)

A
  • Quinolones
  • Fluoroquinolones
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5
Q

Antimicrobial group that inhibits metabolic pathways (1)

A

Sulfonamides

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6
Q

List antimicrobial groups that disrupt cell membrane integrity (2)

A
  • Polymixins
  • Colistins
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7
Q

Cause and Corrective Action: colonies within ZOI

A

Cause:
- mutant, resistant
- mixed culture

Correction:
- re-test with next generation antibiotics
- isolate pure colonies and re-test

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8
Q

Cause and Corrective Action: overlapping ZOI

A

Cause:
- discs too close

Correction:
- use <5 discs/ plate
- spread discs further apart

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9
Q

Cause and Corrective Action: QC zones too small

A

Cause:
- inoculum too heavy
- agar too thick

Correction:
- re-test 0.5 McFarland standard
- ensure 3-5mm depth

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10
Q

Cause and Corrective Action: hazy zones with SXT disc

A

Cause:
- thymidine inhibits mechanism of action

Correction:
- read at 80%

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11
Q

Cause and Corrective Action: QC zones too large

A

Cause:
- inoculum too light
- agar too thin
- nutritionally poor medium
- slow growing organism

Correction:
- re-test 0.5 McFarland standard
- ensure 3-5mm depth
- ensure MIC procedure is used (Mueller-Hinton agar)

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12
Q

Describe the principle of automated methods for antimicrobial therapy

A
  • automated inoculation into 64-well, closed cards containing specified [antibiotics]
  • cards are incubated and temp-regulated
  • optical reading measures T, including the growth control well
  • algorithms are used to interpret and assign MIC values
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13
Q

Explain oxacillin disk testing for Streptococcus pneumoniae

A
  • sterile sits are tested for penicillin resistance
  • R ≤19 mm
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14
Q

Discuss the principle of the beta-lactamase test

A
  • when β-lactamase is produced by an organism, the β-lactam ring is hydrolyzed = forms penicilloic acid
  • cleavage = INACTIVATION of antibiotic
  • decreased pH turns bromcresol purple TO YELLOW
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15
Q

Screening media, follow up testing and significance for MRSA

A

MRSA; methicillin resistant S. aureus
- MecA = penicillin binding protein is altered

Detection:
- chromagar
- cefoxitin

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16
Q

Screening media, follow up testing and significance for VRE

A

VRE; vancomycin resistant enterococci
- VanA/B/E = altered binding site

Detection:
- sens
- VRE chromagar

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17
Q

Describe testing and significance of ESBLs

A

ESBL; extended spectrum beta-lactamase

Detection:
- If cephalosporin is R = do ESBL disc test
- any specimen R to 3rd gen require further testing

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18
Q

Describe the theory and application of the D-test

A
  • If Erythromycin = R, and Clindamycin is S, perform D-test
  • when 2 discs are together, Clindamycin may actually be R
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19
Q

What is Quality Assurance ?

A
  • monitors ongoing QUALITY OF TOTAL TESTING PROCESS (effectiveness of policies and procedures)
  • identify/ correct issues to assure accurate, reliable and prompt results
  • ASSESSES COMPETENCY of staff (pre-, analytical, post-)
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20
Q

What is Quality Control ?

A
  • PROCEDURES that monitor the quality of a testing method to assure accuracy/ reliability of results
  • QC differs from QA in that it is specific to evaluating ANALYTICAL ASPECT of testing
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21
Q

Describe mechanical component of a QC Program

A
  • temp checks of equipment
  • routine cleaning/ defrost of fridges
  • check anaerobic and CO2 conditions
  • check airflow of BSC
  • maintenance
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22
Q

When should incubators and fridges be cleaned inside ?

A

every 3 months

23
Q

When should freezers be defrosted ?

A

every 6 months

24
Q

When should biological spore strips be performed on autoclaves ?

A

every month

25
Q

__ indicators monitor temp and pressure of autoclaves

A

CHEMICAL indicators monitor temp and pressure of autoclaves

26
Q

Biological controls for these conditions: anaerobic, CO2, and microaerophilic

A

Anaerobic: Clostridium haemolyticum
CO2: Neisseria gonorrhoeae
Microaerophilic: Campylobacter jejuni

27
Q

How is media sterility tested ?

A

If <100 plates, incubate all plates at 35°C for 24h, and subsequently at RT for 24h

If >100, test random 2-5% of plates

28
Q

How is performance testing done on media ? Give examples

A
  • assesses nutrient quality and reliability of selective agents

Eg.
CHOC = N. gonorrhoeae
MAC = dry pk E. coli, no spr Proteus, ng S. aureus

NOTE: use ATCC strains

29
Q

Role of internal proficiency testing

A
  • check for errors in equipment/ material use
  • checks sensitivity of methods and ability of staff to ID pathogens; (unknown organism introduced into workflow, accompanied by a req)
30
Q

How is external proficiency testing done ?

A
  • samples are received at predetermined times from external associations
  • specimens labelled as “QC” are processed normally and results are evaluated by the pathologist and supervisor
31
Q

Which of the following antimicrobials inhibit bacterial cells by inhibition of protein synthesis?

Select all that apply:

a.
Chloramphenicol

b.
Tobramycin

c.
Clindamycin

d.
Tetracycline

A

Which of the following antimicrobials inhibit bacterial cells by inhibition of protein synthesis?

a.
Chloramphenicol

b.
Tobramycin

c.
Clindamycin

d.
Tetracycline

32
Q

QC bugs for Oxidase

A

Pseudomonas aeruginosa (+) / Escherichia coli (-)

33
Q

QC bugs for PYR

A

Enterococcus faecalis (+) / Streptococcus bovis (-)

34
Q

QC bugs for germ tube test

A

Candida albicans (+) / Candida tropicalis (-)

35
Q

QC bugs for ALA

A

Haemophilus parainfluenzae (+) /Haemophilus influenzae (-)

36
Q

QC bugs for Butyrate esterase

A

Moraxella catarrhalis (+) / Neisseria lactamica (-)

37
Q

QC bugs for Slide Coag

A

Staphylococcus aureus (+) / Staphylococcus epidermidis (-)

38
Q

QC bugs for Spot Indole

A

Escherichia coli (+) / Proteus mirabilis (-)

39
Q

QC bugs for Catalase

A

Staphylococcus aureus (+) / Streptococcus pyogenes (-)

40
Q

QC bugs for TSB broth at 42°C

A

Pseudomonas aeruginosa (+)/ Pseudomonas fluorescens (-)

41
Q

QC bugs for DNAse

A

(+):
S. aureus
Serratia
M. catarrhalis
Steno

(-):
other Staph
other Enterobacteriaceae
Other Moraxella sp.
Other NFB

42
Q

QC bugs for ONPG

A

Shigella sonnei (+)/ other Shigella sp. (-)

43
Q

QC bugs for HEK

A

Salmonella (pos; blk)/ E. coli (neg; ylo or ng)

44
Q

QC bugs for SS

A

Shigella sp (pos; clr, wh)/ E. coli (neg; NO GROWTH)

45
Q

The following results are recorded for Staphylococcus aureus:

Erythromycin = R

Clindamycin = S

Which of the following tests is required?

a.
B lactamase test

b.
ESBL test

c.
D-test

d.
No further testing, report as tested

A

c.
D-test

46
Q

Which of the following antimicrobials would test sensitive for an organism producing β-lactamase?

a.
Ampicillin

b.
Oxacillin

c.
Penicillin

d.
Amoxicillin

A

b.
Oxacillin

47
Q

Which of the following organisms is associated with pseudomembranous colitis following treatment with broad spectrum antibiotics?

a.
Corynebacterium diphtheriae

b.
Clostridioides difficile

c.
E. coli O157:H7

d.
Staphylococcus aureus

A

b.
Clostridioides difficile

48
Q

Which of the following terms is used to describe the situation when one antibiotic diminishes the effect of another?

a.
Antagonism

b.
Synergism

c.
Cascading

d.
A narrow spectrum antibiotic

A

a.
Antagonism

49
Q

What is the standard pH and agar depth for a Mueller Hinton plate?

a.
pH 7.0-7.2 / 1-2mm

b.
pH 7.0-7.2 / 4-5mm

c.
pH 7.2-7.4 / 1-2mm

d.
pH 7.2-7.4 / 4-5mm

A

d.
pH 7.2-7.4 / 4-5mm

  • agar is more alkaline to counteract acids produced by organisms = toxic
50
Q

Which of the following statements about the Kirby Bauer method of antimicrobial susceptibility testing is / are correct?

a.
Agar concentration in the medium can vary

b.
Testing must be performed from non-selective media

c.
Non-standardized turbid inoculum is required

d.
Zone sizes are measured to determine susceptibility

A

b.
Testing must be performed from non-selective media

d.
Zone sizes are measured to determine susceptibility

51
Q

Which of the following additives are used in identification of ESBL production?

a.
Clavulanic acid

b.
Ethylenediaminetetraacetic acid

c.
Boric acid

d.
Sulphanilic acid

A

a.
Clavulanic acid

52
Q

Which of the following antimicrobials is the best option for an Escherichia coli urinary tract infection?

a.
Vancomycin

b.
Linezolid

c.
Nitrofurantoin

d.
None of the above

A

c.
Nitrofurantoin

53
Q

Significance of SPICE group

A

Serratia
Providenicia
Indole pos Proteus
Citrobacter
Enterobacteraciaes

  • quickly develops resistance to antibiotics

CSMLS (39 decks)

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