Chapter 3

Question 1

what is defined as a low molecular weight substance produced by a microorganism that at low concentrations inhibits or kills other microorganisms

Answer 1

antibiotic

Question 2

what includes any substance of natural, semisynthetic, or synthetic origin that kills or inhibits the growth of a microorganism but causes little or no damage to the host

Answer 2

antimicrobial

Question 3

true or false:
there are no specific guidelines for dose adjustments on antibiotics

Answer 3

true

Question 4

what are the practical uses of antibiotics

Answer 4

-right antibiotic
-right patient
-right dose
-right duration of action
-right route of administration
-monitor the patient throughly

Question 5

what should be one of the most important considerations when you are choosing an antibiotic

Answer 5

if its effective against the bacteria

Question 6

what type of antibacterial agent only inhibits gram + or gram -

Answer 6

narrow-spectrum

Question 7

what type of antibacterial agent inhibits both gram + and gram -

Answer 7

broad-spectrum

Question 8

true or false:
a pathogen’s susceptibility should be a main point when deciding on the selection of an antibiotic

Answer 8

true

Question 9

what are some differences to consider when setting MIC measurements for drugs

Answer 9

1. concentrations are fixed over time in incubation
2. growth medium may differ physiologically
3. testing doesn’t include host factors
4. growth inhibition is the end point
5. no info on persistent effects
6. virulence factors

Question 10

when designing treatments, what is considered the most important factors governing the selection for clinical veterinary use

Answer 10

Antimicrobial Susceptibility Testing (AST)

Question 11

what may AST results not always provide

Answer 11

accurate prediction of clinical outcome

Question 12

when is there the most concern for AST

Answer 12

no animal species and infection-specific veterinary clinical breakpoints are available

Question 13

what are the 3 parameters to assess a clinical breakpoint

Answer 13

1. epidemiological cut-off value (ECOFF)
2. MIC to define a PK/PD cut off
3. clinical cut-off value

Question 14

what does the epidemiological cut-off value mean

Answer 14

highest MIC for bacteria free of detectable aquired resistance mechanisms

Question 15

what data is combined to result in clinical breakpoints

Answer 15

MIC values
PK/PD indices
clinical outcome results

Question 16

what type of antibiotic kills bacteria

Answer 16

bactericidal

Question 17

what type of antibiotic inhibits bacterial growth without killing them

Answer 17

bacteriostatic

Question 18

what is the lowest concentration of an antimicrobial agent required to prevent the growth of the pathogen

Answer 18

minimum inhibitory concentration

Question 19

what is the lowest concentration of an antimicrobial agent required to kill the pathogen

Answer 19

minimum bactericidal concentration

Question 20

what are the most important drivers of drug efficacy

Answer 20

optimal dosing
pharmacokinetics
tissue penetration

Question 21

at concentrations equal to the MIC of a pathogen, which drug acts bacteriostatic rather than as bactericidal

Answer 21

fluoroquinolones

Question 22

which drug, normally bacteriostatic against most gram-negative bacteria, is bactericidal against Haemophilus influenzae and strep.

Answer 22

chlorampheniol

Question 23

what can vary a drug’s bactericidal activites

Answer 23

intracellular pH
oxygen content
intracellular enzymatic activity

Question 24

which chemical groups of antibiotics are concentration dependent

Answer 24

fluoroquinolones
aminoglycosides
nitroimidazoles
polymixins

Question 25

which chemical groups of antibiotics are time-dependent

Answer 25

penicillins cephalosporines macrolides & triamilides lincosamides phenicols sulfonamides diaminopyrimidines

Question 26

which chemical groups of antibiotics are co-dependent for killing needing duration of exposure and maintained drug concentration

Answer 26

tetracyclines ketolides glycopeptides

Question 27

what are the 2 ways antimicrobial agents are often classified

Answer 27

time-dependent concentration-dependent

Question 28

what can the combination of AUC and MIC values be used to predict

Answer 28

probability of bacterial eradication clinical success

Question 29

what does T/MIC mean

Answer 29

increasing the concentration over the MIC curve will not increase the efficacy of a drug. This drug needs to have a longer time limit at a constant concentration

Question 30

what does AUC/MIC or Cmax/MIC mean

Answer 30

these drugs will need increased drug concentrations above the MIC

Question 31

what can control the achieved concentration

Answer 31

systemic availability

Question 32

what is systemic availability variable by

Answer 32

dosage form route of administration ability of drug to gain access volume distribution

Question 33

true or false: parenteral therapy should never be used in the treatment of severe infections

Answer 33

false it should always be used

Question 34

when would it be most appropriate to use an oral therapy in dogs and cats

Answer 34

mild to moderate infections

Question 35

what will enhance passage of a drug across barriers

Answer 35

inflammation

Question 36

define a synergistic antibacterial combination

Answer 36

combined effects are significantly greater than the independent effects

Question 37

define an antagonistic antibacterial combination

Answer 37

combined effects are significantly less than their independent effects

Question 38

which type of antibiotic interferes with the final stage of peptidoglycan synthesis

Answer 38

beta-lactams

Question 39

what do beta-lactams prevent

Answer 39

formation of bacterial cell wall (inhibit activity of PBPs)

Question 40

what type of action do beta-lactam drugs have on bacteria

Answer 40

bactericidal

Question 41

what causes a difference in susceptibility between gram-positive and gram-negative bacteria

Answer 41

differences in receptors sites (PBPs) relative amount of peptidoglycan present ability of drug to penetrate the outer cell membrane resistance to beta-lactamase enzymes

Question 42

which group of penicillin has procaine as a derivative

Answer 42

benzyl penicillin

Question 43

which group of penicillin has a derivative of cloxacillin, dicloxacillin & oxacillin

Answer 43

anti-staphylococcal isoxazolyl penicillins

Question 44

which group of penicillins has a derivative of ampicillin & amoxicillin

Answer 44

extended - broad spectrum penicillins

Question 45

which group of penicillins has a derivative of ticarcillin

Answer 45

antipseudomonal penicillins

Question 46

which penicillin is the only one whose oral bioavailability is great enough to warrant oral administration

Answer 46

amoxicillin

Question 47

where are penicillins predominantly ionised

Answer 47

plasma

Question 48

how are penicillins eliminated from the body

Answer 48

almost entirely from the kidneys

Question 49

true or false: since penicillin is eliminated through the renal system, glomerular filtration and tubular secretion need to be intact to maintain safe concentrations within the body

Answer 49

true

Question 50

what can be used to increase penicillin resident time in the body

Answer 50

probenecid - inhibits tubular secretion

Question 51

what are penicillins normally synergistic with

Answer 51

aminoglycosides - enhance the penetration of the aminoglycoside of the bacteria

Question 52

what are the possible adverse effects of penicillins

Answer 52

acute anaphylaxis collapse mild hypersensitivity reactions

Question 53

true or false: penicillins are not cross-sensitising or cross-reactive

Answer 53

false

Question 54

what is a possible consequence when taking broad-spectrum penicillins

Answer 54

disturbance of the normal intestinal flora

Question 55

what animals should not be given ampicillin due to their intestinal normal flora containing clostridial colitis

Answer 55

small rodents - rabbits, hamsters, gerbils ect.

Question 56

which antibiotic is inherently more resistant to beta-lactamases than penicillin

Answer 56

cephalosporins

Question 57

which groups of cephalosporin primarily only have gram-positive activity

Answer 57

group 1 group 2

Question 58

which group of cephalosporins have gram-positive and gram-negative activity

Answer 58

group 3

Question 59

which group of cephalosporin has decreased gram-positive but increase gram-negative activity

Answer 59

group 4 group 5 group 6

Question 60

which group of cephalosporin has increased gram-positive and gram-negative activity

Answer 60

group 7

Question 61

what are the 3 mechanisms of resistance to cephalosporins can create

Answer 61

PBP modification reduced permeability increased efflux enzymatic degradation by beta-lactamases

Question 62

what antibiotic are cephalosporins synergistic with

Answer 62

aminoglycosides