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Veterinary Pharmacology > Antibiotics, Pt. 2 > Flashcards

Antibiotics, Pt. 2 Flashcards

1
Q

Inhibitors of cell wall biosynthesis:

A
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2
Q

What was the first alternative to penicillins?

A

Cephalosporins

  • considered to be among the safest antimicrobials
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3
Q

What is the mechanism of action of Cephalosporins? What causes resistance?

A

binds PBPs to interfere with peptidoglycan synthesis

bacterial β-lactamase production

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4
Q

How have the 5 generations of Cephalosporins developed?

A
  1. potent activity against G+, mediocre against G-
  2. not used in vet med - extended spectrum against G- with better cell penetration, and improved resistance to β-lactamase
  3. improved activity against G-, better cell penetration, higher binding to target
  4. improved resistance to β-lactamase, wider spectrum with higher activity against G+ and G-
  5. approved for treatment of critical MRSA infection
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5
Q

What is MRSA? What is the equivalent in animals? How is it treated?

A

methicillin-resistant Staphylococcus aureus (superbug), typically causing sepsis in humans

MRSP (methicillin-resistant Staphylococcus pseudintermedius), typically infected through wounds, surgical sites, and ears

5th generation Cephalosporins - Ceftobiprole

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6
Q

What 2 first-generation Cephalosporins are used in veterinary medicine? What is their therapeutic use?

A
  1. Cephalexin
  2. Cephalothin

antibiotic prophylaxis and treatment of infection in penicillin-intolerant patients of all species

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7
Q

What 6 third-generation Cephalosporins are used in veterinary medicine? What are their therapeutic uses?

A
  1. Ceftiofur - respiratory disease, cattle mastitis, UTI and soft tissue infections
  2. Cefoperazone - soft tissue infections and G- bacteremia in dogs
  3. Cefotaxime - G- sepsis, soft tissue infections, meningitis, and CNS infection in dogs, cats, and foals
  4. Cefpodoxime - skin infections in dogs and cats
  5. Cefixime - UTI, respiratory infections
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8
Q

What Cephalosporins are used for bovine mastitis and bacterial endocarditis in dogs?

A

Ceftiofur

Cefixime

(3rd gen)

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9
Q

What is the mechanism of action of Carbapenems? What is their spectrum like? What 3 are commonly used?

A

bind to penicillin-binding proteins to prevent cell wall biosynthesis

BROAD - G+, G-, aerobic, anaerobic, an Pseudomonas

Imipenem, Meropenem, Doriopenem

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10
Q

What causes resistance to Carbapenems?

A

β-lactamase (carbapenemases) that cleaves β-lactams

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11
Q

What is the mechanism of action of Monobactams? Which ones is most commonly used? What is its therapeutic use?

A

bind to penicillin-binding proteins (PBPs) to prevent cell wall biosynthesis

Aztreonam - reserve antibiotic to treat severe G- infections

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12
Q

What class of β-lactam is less likely for resistance to develop?

A

Monobactams - stable to most β-lactams

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13
Q

What are the main 2 targets of inhibitors of protein biosynthesis?

A
  1. 30S RIBOSOME SUBUNIT - impairs proofreading ability and blocks association with rRNA (Aminoglycosides, Tetracyclines)
  2. 50S RIBOSOME SUBUNIT - blocks peptide bond formation between amino acids (Chloramphenicol, Macrolides, Lincosamides)
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14
Q

How does the bacterial activity of protein synthesis inhibitors compare?

A
  • 30S RIBOSOME target - Aminoglycosides = bactericidal; Tetracyclines = bacteriostatic
  • 50S RIBOSOME target - Florfenicol = bactericidal; Chloramphenicol, Macrolides, Lincosamides = bacteriostatic
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15
Q

How do Aminoglycosides and Tetracyclines compare?

A

AMINOGLYCOSIDES = bactericidal; irreversibly binds to the 30S ribosome and inhibits the rate of protein synthesis and the fidelity of mRNA translation

TETRACYCLINES = bacteriostatic; reversibly binds to 30S ribosome and prevents the attachment of tRNA to the mRNA complex

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16
Q

What is the main therapeutic use of Aminoglycosides? What is the oldest member of the class?

A

bactericidal to G- aerobes

Streptomycin - use has declined

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17
Q

What are 3 common Aminoglycosides? What are they used for?

A
  1. Gentamicin, Amikacin - controls uterine, skin, respiratory, urinary tract, ear, and eye infections and septicemia
  2. Neomycin - enteric infections (orally), skin, ear, and eye infections (topical)
  3. Kanamycin - bacterial enteritis (orally), symptomatic relief of diarrhea
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18
Q

What Aminoglycoside has an expanded spectrum?

A

Gentamicin and Amikacin —> effective against G+

19
Q

What next-generation Aminoglycoside is currently in use? How has it been improved?

A

Plazomicin

lacks nephrotoxic and ototoxic side effects

20
Q

How does the mechanism of action of Aminoglycosides affect their therapeutic use?

A

their uptake includes an oxygen-linked energy-dependent step —> only works against aerobic bacteria

21
Q

How does the chemical structure of Aminoglycosides affect their distribution?

A

highly polar, poorly lipid soluble

  • minimum distribution into the CNS
  • accumulates in renal cortex and otic endolymph
  • poorly absorbed from GI tract
22
Q

What causes resistance against Aminoglycosides? What 2 are exceptions?

A

inactivation of various bacterial enzymes

  1. Amikacin
  2. Plazomicin
23
Q

What 3 adverse effects are commonly caused by Aminoglycosides?

A
  1. nephrotoxic
  2. ototoxic
  3. neurotoxic (neuromuscular blockade)
24
Q

What is the therapeutic uses of Tetracyclines?

A

BROAD SPECTRUM: G- and G+; aerobes and anaerobes + bacteriostatic

25
Q

What 3 Tetracycles are used in large animals? What is their use?

A
  • Tetracycline/Chlortetracycline - local and systemic bacterial, chlamydial, rickettsial, and protozoal infections
  • Oxytetracycline - feed additive/growth promoters in cows and pigs
26
Q

What 2 Tetracyclines are used in small animals? What is their use?

A
  1. Doxycycline - respiratory infections and UTIs
  2. Minocycline - abscesses that do not respond to β-lactams
27
Q

What Tetracycline can be used in foals? What are they used for?

A

Tetracycline - contracted tendons

28
Q

What 2 Tetracyclines are able to penetrate the CNS, eye, and prostate?

A
  1. Doxycycline
  2. Minocycline

lipophilic

29
Q

What causes resistance to Tetracyclines?

A

decreased drug uptake or active transport of Tetracycline out of the bacterial cell

30
Q

What 4 adverse effects are common with Tetracycline use?

A
  1. nephrotoxic
  2. discoloration of developing teeth
  3. GI suprainfections of fungi, yeast, or resistant bacteria
  4. RARE: photosensitivity and hepatotoxicity
31
Q

What 3 inhibitors of protein synthesis target the 50S ribosome? What is their mechanism of action?

A
  1. Chloramphenicol - bacteriostatic; binds 50S ribosome and inhibits peptide bond formation and protein synthesis
  2. Macrolides - bacteriostatic; binds 50S ribosome to prevent translocation of amino acids to the growing peptide chain and inhibits protein synthesis
  3. Lincosamides - bacteriostatic; binds 50S ribosome to prevent translocation of amino acids to the growing peptide chain and inhibits protein synthesis
32
Q

What is the therapeutic use of Chloramphenicol and Florfenicol? How do they compare?

A

broad spectrum, including anaerobes

  • Chloramphenicol = bacteriostatic
  • Florfenicol = bactericidal
33
Q

What are Chloramphenicol and Florfenicol used to treat? How do their adverse effects compare?

A
  • Chloramphenicol = local and systemic infections; aplastic anemia
  • Florfenicol = respiratory infections in cows and pigs, footrot in cows; NO aplastic anemia
34
Q

How is Chloramphenicol distributed? How does its usage in animal species compare to Florenicol?

A

absorbed to all tissues, including CNS and eye

it is illegal to use Chloramphenicol in food-producing animals

35
Q

What is the therapeutic use of Macrolides? What 3 are commonly used?

A

bacteriostatic against G+, aerobes, anaerobes, Mycoplasma

  1. Erythromycin
  2. Azithromycin
  3. Tylosin
36
Q

What is Erythromycin used for? Azithromycin?

A

alternative to Penicillin - enteritis and pneumonia

alternative to Erythromycin - Staphylococcus, Strptococcus, and Mycoplasma infections, pneumonia

37
Q

What are the 2 most common uses of Tylosin? What caution needs to be taken?

A
  1. local and systemic infections caused by Mycoplasma and G+
  2. chronic colitis/IBD and respiratory issues

becomes cross-resistant with Erythromycin

38
Q

What are the 2 causes of Macrolide resistance?

A
  1. decreased binding to 50S ribosome
  2. enzymatic inactivation
39
Q

What is the therapeutic use of Lincosamides?

A

bacteriostatic primarily against G+ aerobes and obligate anaerobes

40
Q

What are the 2 uses of Lincomycin? What animals is it used in?

A
  1. dysentery
  2. Staphylococcal, Streptococcal, and Mycoplasma infections

pigs

41
Q

What are 4 uses of Clindamycin? How does it compare to Lincomycin?

A
  1. periodontal disease
  2. osteomyelitis
  3. dermatitis
  4. deep soft tissue infections caused by G+ bacteria
    - in dogs and cats

more potent

42
Q

What Lincosamide is used for bovine mastitis?

A

Pirlimycin

43
Q

What causes Lincosamide resistance? What do they commonly cross-react with?

A

altered binding to 50S ribosome

Macrolides

44
Q

What fatal adverse effect is caused by Lincosamides?

A

fatal diarrhea due to altered GI flora in horses, rabbits, hamsters, and guinea pigs

Veterinary Pharmacology (35 decks)

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