Abx

Question 1

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

Answer 1

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

Question 2

What is the difference between an antibiotic and an antimicrobial?

Answer 2

Abx = naturally derivedAntimicrobial = lab derived

Question 3

What is bacteriostatic?

Answer 3

Inhibiting growth of bacteria, but not actually killing them

Question 4

What is bactericidal?

Answer 4

Killing bacteria

Question 5

When would you use a bacteriostatic drug?

Answer 5

When host defenses can be counted on

Question 6

When would you use a bactericidal drug?

Answer 6

Immunocompromised, prophylacticly, or with lethal strains of bacteria

Question 7

What is antibiotic synergism?

Answer 7

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

Question 8

What is antibiotic antagonism?

Answer 8

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

Question 9

What are broad spectrum abx?

Answer 9

Abx that are effective against a large variety of bacteria

Question 10

What are the advantages and disadvantages of broad spectrum abx?

Answer 10

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

Question 11

What are narrow spectrum abx?

Answer 11

Abx that are effective against only a small subset of bacteria

Question 12

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

Answer 12

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

Question 13

Do abx cause resistance?

Answer 13

No, genetic mutations do

Question 14

What are the three results of an abx test?

Answer 14

SensitiveIntermediateResistant

Question 15

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

Answer 15

Target the abx to the body sites and increase dosage

Question 16

Why should pts alway finish their dose of abx?

Answer 16

To allow immune system to kill off any surviving resistant cells

Question 17

What is empiric therapy for abx?

Answer 17

Treatment while waiting for lab results (broad spectrum abx)

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

What is the MIC?

Answer 20

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

Question 21

What is the MBC?

Answer 21

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

Question 22

What is the E-test?

Answer 22

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

Question 23

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

Answer 23

When discs are placed on an agar plate with bacteria dividing

Question 24

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

Answer 24

it disrupts peptidoglycan synthesis

Question 25

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

Answer 25

Dividing bacteria

Question 26

What are membrane active abx?

Answer 26

Abx that interfere or disrupts with the membrane

Question 27

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

Answer 27

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

Question 28

What is the MOA of Beta-lactams?

Answer 28

Inhibits cell wall synthesis

Question 29

What type of abx are penicillins?

Answer 29

B-lactam

Question 30

What type of abx are cephalosporins?

Answer 30

B-lactams

Question 31

What type of abx are cephamycins?

Answer 31

B-lactams

Question 32

What type of abx are carbaenems? Monobactams?

Answer 32

B-lactams

Question 33

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

Answer 33

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

Question 34

Are beta-lactams bacteriocidal or inhibitory?

Answer 34

Bacteriocidal

Question 35

What type of bacteria are B-lactams ineffective against?

Answer 35

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

Question 36

What is the difference between cephalosproins and penicillin?

Answer 36

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

Question 37

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

Answer 37

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

Question 38

What is the MOA of Vancomycin?

Answer 38

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

Question 39

How is resistance to Vanco brought about?

Answer 39

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

Question 40

What is the MOA of bacitracin?

Answer 40

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

Question 41

Are tetracyclines bacteriostatic or bacteriocidal?

Answer 41

bacteriostatic

Question 42

What is the MOA of tetracyclines?

Answer 42

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.

Question 43

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

Answer 43

yes

Question 44

Are tetracyclines considered broad or narrow spectrum abx?

Answer 44

Broad

Question 45

What is the MOA of aminoglycosides?

Answer 45

They irreversibly bind to the 30S ribosomal subunit

Question 46

Are ainoglycoside generally bactericidal or bacteriostatic?

Answer 46

Bactericidal

Question 47

What type of bacteria are aminoglycosides ineffective against?

Answer 47

Anearobic bacteria

Question 48

What type of abx is gentamycin?

Answer 48

Aminoglycoside

Question 49

What type of abx is streptomycin?

Answer 49

Aminoglycoside

Question 50

What type of abx is kanamycin?

Answer 50

Aminoglycoside

Question 51

What type of abx is neomycin?

Answer 51

Aminoglycoside

Question 52

What is the MOA of macrolides?

Answer 52

bind to the 50S ribosomal subunit

Question 53

Are macrolides bacteriocidal or bacteriostatic?

Answer 53

bacteriostatic

Question 54

What type of abx is clarithromycin?

Answer 54

Macrolides

Question 55

What type of abx is azithromycin?

Answer 55

Macrolides

Question 56

What type of abx is erythremycin?

Answer 56

Macrolides

Question 57

What type of abx is dirithromycin?

Answer 57

Macrolides

Question 58

What type of abx is roxithromycin?

Answer 58

Macrolides

Question 59

What type of abx is telithroomycin?

Answer 59

Macrolides

Question 60

When are macolides generally used?

Answer 60

When pt has an allergy to penicillin

Question 61

What is the MOA of Quinolones?

Answer 61

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

Question 62

Are Quinolones bactericidal or bacteristatic?

Answer 62

Bacteriocidal

Question 63

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

Answer 63

Quinolones

Question 64

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

Answer 64

Binds to and inhibits RNA polBacteriocidal

Question 65

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

Answer 65

Toxic compound to DNABactericidal

Question 66

What are antimetabolites?

Answer 66

Abx that inhibit a part of bacterial metabolism

Question 67

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

Answer 67

Antimetabolite MOA = inhibits folate synthesis

Question 68

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

Answer 68

Antimetabolite MOA = inhibits folate synthesis

Question 69

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

Answer 69

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