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Flashcards in Abx Deck (69):
1

What is meant by the term, "selective toxicity"?

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

2

What is the difference between an antibiotic and an antimicrobial?

Abx = naturally derivedAntimicrobial = lab derived

3

What is bacteriostatic?

Inhibiting growth of bacteria, but not actually killing them

4

What is bactericidal?

Killing bacteria

5

When would you use a bacteriostatic drug?

When host defenses can be counted on

6

When would you use a bactericidal drug?

Immunocompromised, prophylacticly, or with lethal strains of bacteria

7

What is antibiotic synergism?

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

8

What is antibiotic antagonism?

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

9

What are broad spectrum abx?

Abx that are effective against a large variety of bacteria

10

What are the advantages and disadvantages of broad spectrum abx?

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

11

What are narrow spectrum abx?

Abx that are effective against only a small subset of bacteria

12

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

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

13

Do abx cause resistance?

No, genetic mutations do

14

What are the three results of an abx test?

SensitiveIntermediateResistant

15

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

Target the abx to the body sites and increase dosage

16

Why should pts alway finish their dose of abx?

To allow immune system to kill off any surviving resistant cells

17

What is empiric therapy for abx?

Treatment while waiting for lab results (broad spectrum abx)

18

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

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

19

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

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

20

What is the MIC?

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

21

What is the MBC?

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

22

What is the E-test?

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

23

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

When discs are placed on an agar plate with bacteria dividing

24

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

it disrupts peptidoglycan synthesis

25

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

Dividing bacteria

26

What are membrane active abx?

Abx that interfere or disrupts with the membrane

27

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

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

28

What is the MOA of Beta-lactams?

Inhibits cell wall synthesis

29

What type of abx are penicillins?

B-lactam

30

What type of abx are cephalosporins?

B-lactams

31

What type of abx are cephamycins?

B-lactams

32

What type of abx are carbaenems? Monobactams?

B-lactams

33

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

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

34

Are beta-lactams bacteriocidal or inhibitory?

Bacteriocidal

35

What type of bacteria are B-lactams ineffective against?

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

36

What is the difference between cephalosproins and penicillin?

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

37

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

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

38

What is the MOA of Vancomycin?

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

39

How is resistance to Vanco brought about?

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

40

What is the MOA of bacitracin?

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

41

Are tetracyclines bacteriostatic or bacteriocidal?

bacteriostatic

42

What is the MOA of tetracyclines?

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

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

yes

44

Are tetracyclines considered broad or narrow spectrum abx?

Broad

45

What is the MOA of aminoglycosides?

They irreversibly bind to the 30S ribosomal subunit

46

Are ainoglycoside generally bactericidal or bacteriostatic?

Bactericidal

47

What type of bacteria are aminoglycosides ineffective against?

Anearobic bacteria

48

What type of abx is gentamycin?

Aminoglycoside

49

What type of abx is streptomycin?

Aminoglycoside

50

What type of abx is kanamycin?

Aminoglycoside

51

What type of abx is neomycin?

Aminoglycoside

52

What is the MOA of macrolides?

bind to the 50S ribosomal subunit

53

Are macrolides bacteriocidal or bacteriostatic?

bacteriostatic

54

What type of abx is clarithromycin?

Macrolides

55

What type of abx is azithromycin?

Macrolides

56

What type of abx is erythremycin?

Macrolides

57

What type of abx is dirithromycin?

Macrolides

58

What type of abx is roxithromycin?

Macrolides

59

What type of abx is telithroomycin?

Macrolides

60

When are macolides generally used?

When pt has an allergy to penicillin

61

What is the MOA of Quinolones?

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

62

Are Quinolones bactericidal or bacteristatic?

Bacteriocidal

63

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

Quinolones

64

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

Binds to and inhibits RNA polBacteriocidal

65

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

Toxic compound to DNABactericidal

66

What are antimetabolites?

Abx that inhibit a part of bacterial metabolism

67

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

Antimetabolite MOA = inhibits folate synthesis

68

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

Antimetabolite MOA = inhibits folate synthesis

69

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

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