Section 2

Question 1

How do the mechanisms of action of bactericidal and bacteriostatic medication differ?

Answer 1

Bactericidal - interfere with cell wall/nucleic acid synthesis
Bacteriostatic - inhibit protein synthesis

Question 2

What are the concentration-dependent antibiotic groups?

Answer 2

Fluoroquinolones and aminoglycosides

Question 3

Which antibiotics are lipid soluble?

Answer 3

Rifampin, fluoroquinolones, TMPS, chloramphenicol

Question 4

Which antibiotics are excreted in active form through the liver and concentrated in bile?

Answer 4

Doxycycline and ampicillin

Question 5

Give examples (2) of bacteria with innate resistance to antibiotics

Answer 5

Enterococci and cephalosporins - lack binding proteins to bind ABs
Anaerobic bacteria and aminoglycosides - O2 needed for entry into cell

Question 6

What family of antiviral agent are acyclovir and famcyclovir? What is their MOA?

Answer 6

Antiherpesviral - guanosine analogue
Activated by herpesvirus thymidine kinase - phosphorylates
Further phosphorylated by host cell enzymes - concentrate in virus-infected cells and inhibit DNA polymerase
Famcyclovir = prodrug

Question 7

What side effects are associated with systemic acyclovir?

Answer 7

Myelosuppression, renal tubular necrosis, hepatic necrosis (all cats)

Question 8

How is famcyclovir tolerated in cats?

Answer 8

High doses required
Well tolerated

Question 9

What are Idoxuridine and Trifluridine? What is their MOA/clinical application?

Answer 9

Antiherpesviral
Halogenated thymidine analogues
Toxic systemically
Trifuridine - better corneal penetration, expensive, irritating

Question 10

What is vidarabine?

Answer 10

Antiherpesviral
Adenosine analogue

Question 11

What is lysine?

Answer 11

Antiherpesviral
Amino acid - poorly understood mechanism

Question 12

What is the evidence for lysine use in cats?

Answer 12

Shown to be effective in treating and reducing shedding in cats with FHV-1 conjunctivitis
Several studies shown that supplementation does not prevent response signs in shelter cats

Question 13

What is zidovudine (AZT)? What is it’s MOA?

Answer 13

Antiretroviral
Thymidine analogue

Question 14

What are the side effects of zidovudine (AZT)?

Answer 14

Non-regenerative anaemia, neutropenia

Question 15

What is oseltamivir? What is it’s MOA?

Answer 15

Tamiflu - antiinfluenza
Neuraminidase inhibitor - surface glycoprotein of influenza A/B

Question 16

What is the MOA of beta-lactam ABs?

Answer 16

Bind and inhibit penicillin binding proteins - needed for cross-linking peptidoglycan layer of bacterial cell walls. Cell walls constantly remodelled, hydrolases still active. Ends in cell rupture

Question 17

Which bacteria are more sensitive to beta-lactam ABs?

Answer 17

G+ve - have thicker cell walls

Question 18

What are the mechanisms of B-lactam resistance?

Answer 18

B-lactamase
Altered penicillin-binding proteins
G-ve - exclusion of drugs that would diffuse through porins

Question 19

Are beta-lactams time or concentration dependent? How long is their half life?

Answer 19

Time
Short half life

Question 20

What b-lactam inhibitors are available?

Answer 20

Clavulanic acid, sulbactam and tazobactam

Question 21

How are beta-lactams excreted?
Do they penetrate the BBB?

Answer 21

Renal
Poor penetration of BBB

Question 22

How are cephalosporines excreted?
Do they penetrate the BBB?

Answer 22

Renal
Poor penetration of BBB

Question 23

What family of drug is vancomycin? What is its MOA?

Answer 23

Glycopeptide
Inhibits cell wall synthesis

Question 24

What drugs inhibit nucleic acid?

Answer 24

Fluoroquinolones, metronidazole, rifamycin, TMPS

Question 25

What in the MOA of fluoroquinolones?

Answer 25

Bind to DNA gyrase and topoisomerase IV - disrupts bacterial DNA synthesis

Question 26

What affects fluoroquinolones efficacy against G+ve/G-ve bacteria?

Answer 26

DNA gyrase - G-ve Topoisomerase - G+ve

Question 27

Rank fluoroquinolones based on anaerobic activity?

Answer 27

Pradofloxacin > Marbofloxacin > Enrofloxacin

Question 28

Which antibiotic(s) are associated with retinal injury in cats? What is the prognosis?

Answer 28

Enrofloxacin Can resolve following withdrawal

Question 29

Which antibiotics are associated with false positive on urine glucose dipsticks?

Answer 29

Cephalosporines and fluoroquinolones

Question 30

Metronidazole - cidal or static?

Answer 30

Cidal

Question 31

Metronidazole MOA

Answer 31

Diffuses into bacterial cells as prodrug, activated in cytoplasm. Generates free radicals and damages DNA

Question 32

What is the mechanism of metronidazole's immunomodulatory activity?

Answer 32

Scavenges ROS Modulates neutrophil activity

Question 33

What is the main side effect of metronidazole and how is it treated?

Answer 33

Neurotoxicity Diazepam

Question 34

Ri

Question 35

Rifamycins - cidal or static?

Answer 35

Cidal

Question 36

Rifamycins MOA?

Answer 36

Inhibit DNA-dependent RNA polymerase - impaired RNA synthesis

Question 37

Is rifampin lipid soluble?

Answer 37

Very - allows high intracellular concentration, can be used to treat intracellular infections (eg mycobacterium/brucella)

Question 38

Rifampin - side effects?

Answer 38

Vomiting, anorexia. Red discolouration of body fluids. Hepatopathy

Question 39

TMPS - MOA?

Answer 39

Inhibit bacterial folate metabolism - interferes with purine synthesis

Question 40

TMPS - static or cidal?

Answer 40

Separately static, together cidal

Question 41

TMPS - spectrum?

Answer 41

Broad

Question 42

TMPS - acid or base?

Answer 42

Weak base

Question 43

Which antibiotics inhibit protein synthesis?

Answer 43

Aminoglycosides, chloramphenicol, tetracyclines

Question 44

Aminoglycosides - MOA

Answer 44

Multiple Bind electrostatic ally to bacterial wall - dispose Ca and Mg (greater in G-ve) - disrupt permeability Taken up by cell, trapped in cytoplasm Bind to 30S subunit

Question 45

What type of infection are aminoglcyosides ineffective against?

Answer 45

Anaerobic - MOA O2 dependent

Question 46

Aminoglycosides - oral bioavailability?

Answer 46

Very poor

Question 47

Aminoglycosides - cidcl or static?

Answer 47

Cidal

Question 48

Aminoglycosides - water or lipid soluble?

Answer 48

Water

Question 49

Aminoglycosides - time or concentration dependent?

Answer 49

Concentration

Question 50

Aminoglycosides - adverse effects?

Answer 50

Nephrotoxicity, ototoxicity, neuromuscular blockade

Question 51

Chloramphenicol - MOA

Answer 51

Binds to 50S subunit of bacterial ribosome

Question 52

Chloramphenicol - cidal or static?

Answer 52

Traditionally thought of as static, recent evidence cidal

Question 53

Chloramphenicol - spectrum

Answer 53

Broad

Question 54

Chloramphenicol - lipid/water soluble?

Answer 54

Lipid

Question 55

Chloramphenicol side effects

Answer 55

Reversible bone marrow suppression

Question 56

List macrolides and lincosamides

Answer 56

M - erythromycin, tylosin, clarithromycin, azithromycin L - clindamycin, lincomycin

Question 57

Macrolides/lincosamides - MOA

Answer 57

Bind to 50S subunit

Question 58

Macrolides/lincosamides - cidal or static?

Answer 58

Static

Question 59

Tetracyclines - MOA

Answer 59

Bind to 30S

Question 60

Tetracyclines - cidal or static?

Answer 60

Static

Question 61

Tetracyclines - lipid or water soluble?

Answer 61

Lipid