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Clinical Bacteriology > (M) Lec 6.2: Antimicrobial Susceptibility Testing > Flashcards

(M) Lec 6.2: Antimicrobial Susceptibility Testing Flashcards

1
Q

What are the three different antimicrobial agents?

A
  1. Antibacterial agents
  2. Antiviral agents
  3. Antifungal agents
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2
Q

This antimicrobial agent is destructive to and inhibits bacteria.

A

Antibacterial agents

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3
Q

This antimicrobial agent weakens and inhibits viruses.

A

Antiviral agents

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4
Q

This antimicrobial agent inhibits fungi.

A

Antifungal agents

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5
Q

What are the two categories of antimicrobial agents?

A
  1. Bacteriocidal agents
  2. Bacteriostatic agents
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6
Q

This type of antimicrobial agent kills the microbes (eg. penicillins, cephalosporins, and vancomycin)

A

Bacterocidal agents

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7
Q

This type of antimicrobial agent inhibits the growth (eg. tetracycline, sulfonamides, erythromycin)

A

Bacteriostatic agents

Clue: Static, meaning walang growth

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8
Q

T or F: Categories may overlap which depends on the dosage, route of administration, and site of infection.

A

T

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9
Q

Categories may overlap depending on what three factors?

A
  1. Dosage
  2. Route of administration
  3. Site of infection
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10
Q

This type of antibiotic has limited spectrum like penicillin G for gram positive organisms.

A

Narrow-spectrum antibiotics

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11
Q

This type of antibiotic has a wide spectrum against both gram positive and gram negative like tetracycline.

A

Broad-spectrum antibiotics

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12
Q

Which type of spectrum inhibits and destructs the normal flora of the patient and is a secondary infection or superinfection?

A

Broad-spectrum antibiotics

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13
Q

What are the things to consider in the selection of the antimicrobial agent?

A
  1. Effect to the organism
  2. Toxicity level to the host and to normal flora
  3. Pharmacological activities and allergic reactions
  4. Host’s immune system, medical considerations, and organ functions
  5. Solubility
  6. Age of the patient, site of infection, and route of administration
  7. Toxic to fetus and crosses the placenta or BBB
  8. Cost effectiveness
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14
Q

What are the four categories/types of antibiotics?

A
  1. Cell wall inhibiting
  2. Altering bacterial cell membranes
  3. Inhibits protein synthesis
  4. Inhibits folic acid synthesis
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15
Q

Cell Wall Inhibiting Antibiotics

This type of antibiotic contains the B lactam ring.

A

Beta lactam antibiotics

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16
Q

Cell Wall Inhibiting Antibiotics

Nucleotide intermediates accumulate in the cell wall = ?

A

Inhibition of cell wall synthesis

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17
Q

Cell Wall Inhibiting Antibiotics

Penicillin G and V are formed from?

A

Mold Penicillum notatum

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18
Q

Cell Wall Synthesis Antibiotics

What is the spectrum of synthetic aminopenicillins, ampicillin, amoxicillin, and bacampicillin?

A

Gram positive other than Staphylococcus (resistant)

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19
Q

Altering Bacterial Cell Membranes Antibiotics

This antibiotic binds to the outer surface of the cell membrane and alter phospholipids.

A

Bacitracin antibiotics

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20
Q

Altering Bacterial Cell Membranes Antibiotics

Source of bacitracin antibiotics?

A

Bacillus licheniformis

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21
Q

Altering Bacterial Cell Membranes Antibiotics

What is the spectrum of bacitracin antibiotics?

A

Gram positive including Staphylococcus and some gram negative

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22
Q

Altering Bacterial Cell Membranes Antibiotics

What is the spectrum of Polymyxins B and E (Colistin)?

A

Gram negative

Used as topical agents for burns and wound infections

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23
Q

Inhibits Protein Synthesis Antibiotics

These antibiotics interfere with protein synthesis.

A
  1. Aminoglycosides
  2. Erythromycin
  3. Chloramphenicol

Aminoglycosides: Streptomycin, Tobramycin, and Gentamycin

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24
Q

Inhibits Protein Synthesis Antibiotics

Source of Streptomycin?

A

Streptomyces griseus

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25
Q

Inhibits Protein Synthesis Antibiotics

What is the spectrum for Streptomycin?

A

Combination for Tb and B lactam enterococcus

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26
Q

Inhibits Protein Synthesis Antibiotics

Source of Gentamycin?

A

Micromonospora purpurea

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27
Q

Inhibits Protein Synthesis Antibiotics

What is the spectrum for Gentamycin?

A

Generally, gram negative bacilli

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28
Q

Inhibits Protein Synthesis Antibiotics

Source of Tobramycin?

A

Streptomyces fradiae

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29
Q

Inhibits Protein Synthesis Antibiotics

What is the spectrum for Tobramycin?

A

Recommended in showing resistance to Gentamycin

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30
Q

Inhibits Protein Synthesis Antibiotics

What is the spectrum for Erythromycin?

A

Gram positive, S. pyogenes, S. pneumoniae (Penicillin-resistant), M. pneumoniae, Legionella, Neisseria, and Haemophilus

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31
Q

Inhibits Protein Synthesis Antibiotics

What is the spectrum for Chloroamphenicol?

A

Gram positive and gram negative

32
Q

What are the five types of antibiotics that inhibit folic acid synthesis?

A
  1. Sulfonamides
  2. Quinolones
  3. Nitrofurantoin
  4. Rifampin
  5. Metronidazole
33
Q

Inhibits Folic Acid Synthesis Antibiotics

Competitive inhibition of folic acid synthesis

A

Sulfonamides

34
Q

Inhibits Folic Acid Synthesis Antibiotics (Sulfonamides)

Used primarily for acute UTI

A

Sulfamethoxazole

35
Q

Inhibits Folic Acid Synthesis Antibiotics (Sulfonamides)

Inhibits enzyme dihydrofolate reductase

A

Trimethoprim

36
Q

Inhibits Folic Acid Synthesis Antibiotics (Sulfonamides)

Treatment of chronic UTI and Enterobacteriaceae infection

A

Trimethoprim-sulfamethoxazole

37
Q

Inhibits Folic Acid Synthesis Antibiotics

Inhibition of DNA gyrase activity which interferes with synthesis of DNA

A

Quinolones

38
Q

Inhibits Folic Acid Synthesis Antibiotics (Quinolones)

Treats UTI

A

Nalidixic Acid

39
Q

Inhibits Folic Acid Synthesis Antibiotics (Quinolones)

Has a broader spectrum and is used as a treatment for UTI and invasive ear infection

A

Fluoroquinolones (Ciprofloxacin)

40
Q

Inhibits Folic Acid Synthesis Antibiotics (Quinolones)

Most effective to UTI (excreted and concentrated)

A

Norfloxacin

41
Q

Inhibits Folic Acid Synthesis Antibiotics

Inhibition of bacterial enzymes or protein synthesis

A

Nitrofurantoin

42
Q

Inhibits Folic Acid Synthesis Antibiotics

Inhibition of DNA-dependent RNA polymerase

43
Q

Inhibits Folic Acid Synthesis Antibiotics

Used in the treatment of Tb and prophylaxis for N. meningitidis

44
Q

Inhibits Folic Acid Synthesis Antibiotics

Cause altered DNA synthesis resulting to bacteriocidal effect

A

Metronidazole

45
Q

Inhibits Folic Acid Synthesis Antibiotics

Activated under anaerobic conditions and treats Gardnerella vaginosis and pseudomembranous colitis from C. difficile

A

Metronidazole

46
Q

Antimycobacterial Agents

Inhibits DNA-dependent RNA polymerase

47
Q

Antimycobacterial Agents

Inteferes in formation of mycolic acid

A

Isoniazid (INH)

48
Q

Antimycobacterial Agents

Bacteriocidal

A

Pyrazinamide (PZA)

49
Q

Antimycobacterial Agents

Bacteriostatic and inhibits mycolic acid

A

Ethambutol

50
Q

Antimycobacterial Agents

Aminoglycoside that is generally used as a second line drug

A

Streptomycin

51
Q

Antifungal Agents

Attacks sterols in fungal cell wall (ergosterols)

A

Amphotericin B

52
Q

Antifungal Agents

Prevents sterol synthesis affecting cell membrane

53
Q

Antifungal Agents

Dermatophytic, yeast, and superficial fungal infection

A

Clotrimazole

54
Q

Antifungal Agents

Binds to ergosterol in fungal cell membrane

55
Q

The preferred laboratory method for susceptibility testing

A

Kirby-Bauer Disk Diffusion Test

56
Q

What makes up Kirby-Bauer Disk Diffusion Test?

A

Standardized suspension + bacteria + MHA + paper disk

57
Q

Lack of growth = zone of inhibition (diameter is measured)

A

Clear Zone

58
Q

Manner of Reporting

Appears to be effective

A

Susceptible (sensitive)

59
Q

Manners of Reporting

Appears to be ineffective

60
Q

Manners of Reporting

In between

A

Intermediate

61
Q

What is the principle of the laboratory method for susceptibility testing?

A

Inverse linear relationship between the diameter of the zone of inhibited growth around the antibiotic disk and the algorithm of the minimal inhibitory concentration (MIC) of the organism

62
Q

T or F: There is a directly proportional linear relationship between the diameter of the zone of inhibited growth around the antibiotic disk and the algorithm of the MIC of the organism.

A

F

Inverse linear relationship

63
Q

Lowest concentration of antibiotic that inhibits in vitro bacterial growth

A

Minimal Inhibitory Concentration (MIC)

64
Q
  • Calcium and Magnesium: activity of aminoglycosides x P. aeruginosa
  • Activity of the tetracycline against all bacteria
  • Calcium and Magnesium lead to activity against these agents
A

Mueller Hinton Agar (MHA)

65
Q

What is the pH for Kirby-Bauer?

A

7.2 to 7.4

66
Q

What is the depth for Kirby-Bauer?

67
Q

Density of the inoculum

A

0.5 McFarland standard

68
Q

Too light inoculum or older culture

A

False susceptible

69
Q

Too heavy inoculum

A

False resistant

70
Q

T or F: Night colonies take less than 24 hours.

71
Q

Thicker zone of inhibition leads to?

A

False resistant

72
Q

Thinner zone of inhibition leads to?

A

False susceptible

73
Q

Incubation for AST?

A

35 deg. Celsius +/- 2 deg. Celsius for 16 to 18 hours

74
Q

T or F: Higher temperature leads to larger zone of inhibition.

A

F

Low temperature

75
Q

T or F: You can stack more than five plates for AST.

A

F

You cannot since the center may not reach the correct temperature.

76
Q

This is needed for fastidious organisms only.

A

Increased CO2

Clinical Bacteriology (33 decks)

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