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Microbio > Abx > Flashcards

Abx Flashcards

1
Q

What is meant by the term, “selective toxicity”?

A

The ability to kill or inhibit growth of a microorganism without harming host cells

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2
Q

What is the difference between an antibiotic and an antimicrobial?

A

Abx = naturally derivedAntimicrobial = lab derived

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3
Q

What is bacteriostatic?

A

Inhibiting growth of bacteria, but not actually killing them

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4
Q

What is bactericidal?

A

Killing bacteria

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5
Q

When would you use a bacteriostatic drug?

A

When host defenses can be counted on

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6
Q

When would you use a bactericidal drug?

A

Immunocompromised, prophylacticly, or with lethal strains of bacteria

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7
Q

What is antibiotic synergism?

A

When a combination of two or more abx have an enhanced activity when administered together

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8
Q

What is antibiotic antagonism?

A

When a combination of abx interfere with one another, and reduce overall effectiveness

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9
Q

What are broad spectrum abx?

A

Abx that are effective against a large variety of bacteria

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10
Q

What are the advantages and disadvantages of broad spectrum abx?

A

Advantage = kill w/o knowing etiologyDisadvantage = kill gut flora

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11
Q

What are narrow spectrum abx?

A

Abx that are effective against only a small subset of bacteria

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12
Q

What are the advantages/disadvantages of using narrow spectrum abx?

A

Advantage: Avoid disrupting normal floraDis: must have specific disease to target

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13
Q

Do abx cause resistance?

A

No, genetic mutations do

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14
Q

What are the three results of an abx test?

A

SensitiveIntermediateResistant

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15
Q

What would you do if you had an intermediate resistance abx, if you still wanted it to be effectie

A

Target the abx to the body sites and increase dosage

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16
Q

Why should pts alway finish their dose of abx?

A

To allow immune system to kill off any surviving resistant cells

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17
Q

What is empiric therapy for abx?

A

Treatment while waiting for lab results (broad spectrum abx)

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18
Q

What are the pharmacokinetic/pharmacodynamic properties of abx that must be considered when administering abx?

A

Concentration of abx at site of infection must be adequate for a prolonged duration

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19
Q

What are the four ways that bacteria break down/avoid death by abx?

A
  1. Hydolysis2. Chemical modification3. Alteration of target4. Altered permeability5. Lack of target
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20
Q

What is the MIC?

A

Minimal inhibitory concentration- A measure of the lowest concentration of the antimicrobial agent that inhibits visible growth of bacteria after 18-24 hours of incubation

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21
Q

What is the MBC?

A

Minimal bactericidal concentration (MBC) – the lowest concentration of antibiotic without visible bacterial growth on agar after 18-24 hours incubation.

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22
Q

What is the E-test?

A

Strips of varying [C] of abx placed on an agar plate with bacteria multiplying.

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23
Q

What is the disk diffusion assay (Kirby-Bauer test)?

A

When discs are placed on an agar plate with bacteria dividing

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24
Q

What does it mean for an abx to be cell wall active?

A

it disrupts peptidoglycan synthesis

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25
Q

What are cell wall active abx effective against/what must the bacteria be doing for it to take effect?

A

Dividing bacteria

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26
Q

What are membrane active abx?

A

Abx that interfere or disrupts with the membrane

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27
Q

Are membrane active abx effective against resting or actively dividing bacteria? How about cell wall active?

A

Membrane active effective against bothCell wall active only effective against dividing bacteria

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28
Q

What is the MOA of Beta-lactams?

A

Inhibits cell wall synthesis

29
Q

What type of abx are penicillins?

A

B-lactam

30
Q

What type of abx are cephalosporins?

A

B-lactams

31
Q

What type of abx are cephamycins?

A

B-lactams

32
Q

What type of abx are carbaenems? Monobactams?

A

B-lactams

33
Q

What is the enzyme that penicillin disrupts? What is the function of this enzyme?

A

Penicillin binding proteins/transpeptidases.This enz crosslinks L-lysine to an alanine in the NAM/NAG of the peptidoglycan chain

34
Q

Are beta-lactams bacteriocidal or inhibitory?

A

Bacteriocidal

35
Q

What type of bacteria are B-lactams ineffective against?

A

against species that lack cell wall (e.g. Mycoplasma), those with very impenetrable walls, or those that produce Beta-lactamase

36
Q

What is the difference between cephalosproins and penicillin?

A

Cephalosporins are more resistant to B-lactamase, and have a longer half-life

37
Q

What are the ways in which resistance to B-lactams is brought about? (4)

A
  1. Altered transpeptidases2. Altered outer membrane permeability3, Presence of efflux pumps4. Chemical modification of abx
38
Q

What is the MOA of Vancomycin?

A

Recognizes and binds to the two D-alanine residue ands of the peptide cchaines of NAM//NAG in peptidoglycan, preventing transpeptidase function

39
Q

How is resistance to Vanco brought about?

A

By changing the D-ala residue on the NAM to a D-lactate, preventing the binding of vanco

40
Q

What is the MOA of bacitracin?

A

Interferes with dephosphorylation of bactoprenol, which carries NAM/NAG residues from the inner to the outer surface of a cell membrane

41
Q

Are tetracyclines bacteriostatic or bacteriocidal?

A

bacteriostatic

42
Q

What is the MOA of tetracyclines?

A

inhibit protein synthesis by binding to the 30S ribosomal subunit of the ribosome and inhibiting the binding of the amino-acyl tRNA to the mRNA-ribosome complex.

43
Q

Do tetracyclines act on both gram positive and gram negative bacteria?

A

yes

44
Q

Are tetracyclines considered broad or narrow spectrum abx?

A

Broad

45
Q

What is the MOA of aminoglycosides?

A

They irreversibly bind to the 30S ribosomal subunit

46
Q

Are ainoglycoside generally bactericidal or bacteriostatic?

A

Bactericidal

47
Q

What type of bacteria are aminoglycosides ineffective against?

A

Anearobic bacteria

48
Q

What type of abx is gentamycin?

A

Aminoglycoside

49
Q

What type of abx is streptomycin?

A

Aminoglycoside

50
Q

What type of abx is kanamycin?

A

Aminoglycoside

51
Q

What type of abx is neomycin?

A

Aminoglycoside

52
Q

What is the MOA of macrolides?

A

bind to the 50S ribosomal subunit

53
Q

Are macrolides bacteriocidal or bacteriostatic?

A

bacteriostatic

54
Q

What type of abx is clarithromycin?

A

Macrolides

55
Q

What type of abx is azithromycin?

A

Macrolides

56
Q

What type of abx is erythremycin?

A

Macrolides

57
Q

What type of abx is dirithromycin?

A

Macrolides

58
Q

What type of abx is roxithromycin?

A

Macrolides

59
Q

What type of abx is telithroomycin?

A

Macrolides

60
Q

When are macolides generally used?

A

When pt has an allergy to penicillin

61
Q

What is the MOA of Quinolones?

A

inhibiting DNA gyrase (topoisomerase II) and/or topoisomerase IV activity of many Gram positive and Gram-negative bacteria

62
Q

Are Quinolones bactericidal or bacteristatic?

A

Bacteriocidal

63
Q

What type of abx are nalidixic acid, ciprofloxacin and the newer fluoroquinolones, such as danofloxacin, difloxacin, enrofloxacin, marbofloxacin, and orbifloxacin.

A

Quinolones

64
Q

What is the MOA of rifampin/rifabutin? Is this baceriocidal or bacteriostatic?

A

Binds to and inhibits RNA polBacteriocidal

65
Q

What is the MOA of metronidazole? Is this bacteriocidal or bacterstatic?

A

Toxic compound to DNABactericidal

66
Q

What are antimetabolites?

A

Abx that inhibit a part of bacterial metabolism

67
Q

What type of abx are sulfonamides? What is the MOA?

A

Antimetabolite MOA = inhibits folate synthesis

68
Q

What type of abx are DHFR inhibitors (trimethoprim)? What is the MOA?

A

Antimetabolite MOA = inhibits folate synthesis

69
Q

Why aren’t drugs that inhibit folate metabolism detrimental to mammals?

A

Mammals get folate from the diet, they do not synthesize it, and so there is selective toxicity.

Microbio (50 decks)

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