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Veterinary Pharmacology > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What is the approval and regulation of animal antibiotics like?

A

FDA reviews and approves animal medicines using the same standards and processes as those for human medicine

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2
Q

What is mostly responsible for the risk of antibiotic resistance? How does this compare in animals?

A

human healthcare use —> overuse and misuse of antibiotics

risk of antibiotic use in animals is extremely low compared to uses in human healthcare settings

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3
Q

What are the 2 major functions of antibiotics?

A
  1. bactericidal - kills bacteria
  2. bacteriostatic - inhibit the growth and proliferation of bacteria, allowing the animal’s immune system to more effectively fight the bacterial infection
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4
Q

What is an antibacterial spectrum? What are the 2 types?

A

range of activity of an antibiotic

  1. BROAD SPECTRUM - antibiotic can inhibit a wide range of Gram + and Gram - bacteria (Carbapenems, 3-4 gen Cephalosporins)
  2. NARROW SPECTRUM - antibiotic is active only against a limited number of bacteria (Penicillin, 1-2 gen Cephalosporins)
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5
Q

How do Gram-positive and Gram-negative bacteria compare?

A

POSITIVE = stains purple due to thick peptidoglycan layers

NEGATIVE = stains pink due to thin peptidoglycan layer and LPS

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6
Q

What 4 characteristics should influence selection of antimicrobial drugs?

A
  1. spectrum of activity
  2. PK and PD - minimal inhibitory concentration
  3. potential side effects
  4. drug sensitivity of bacteria
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7
Q

What antibiotic is Mycoplasma resistant to? Why?

A

Penicillin —> does not contain/produce penicillin-binding protein

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8
Q

What questions should be considered with selecting appropriate antimicrobial agents?

A
  • Is an antimicrobial agent required? Is there an infection that will respond to treatment?
  • Where is the infection? What are the drug access problems to overcome?
  • Which pathogen(s) are usually found at the location of infection?
  • Which antimicrobial agent has the necessary PK to get to the location and get there at a concentration above the minimal inhibitory concentration so that MIC is below the breakpoint?
  • What dose and route are necessary to achieve the desired effect?
  • How long should treatment be for?
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9
Q

What antimicrobial agents are preferred in immunocompromised patients?

A

bactericidal —> immune system may not be functional enough to overcome even a deactivated bacteria

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10
Q

What is important to consider in antibiotic treatments for food-producing animals?

A

residues in milk and meat requires withdrawal times before slaughter

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11
Q

What governs the dosing intervals? Pre-slaughter withdrawal times?

A

drug plasma concentration

tissue residence times

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12
Q

What are 5 mechanisms that bacteria may manifest resistance?

A
  1. bacteria may produce enzymes that deactivate the drug
  2. permeability to or uptake of drug may be decreased
  3. transport out of the cell (MDR1) may be increased
  4. alteration of the drug receptor or binding site may result in reducing the affinity
  5. may develop alternative metabolic/synthetic pathways to bypass or repair effects of drug
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13
Q

What are 4 mechanisms by which bacteria develop resistance?

A
  1. MUTATION: bacteria randomly undergoes chromosomal mutations
  2. CONJUGATION: genetic material is transerred from cell to cell via resistance transfer factor (RIF); infections drug resistance
  3. TRANSDUCTION: transferring drug resistant gene by bacteriophages
  4. TRANSFORMATION: incorporation of naked DNA encoding drug resistance
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14
Q

Bacterial structure:

A

PROKARYOTIC - single-celled, lacking organelles and nucleus

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15
Q

What are the 6 mechanisms of actions of different antibacterial cells?

A
  1. block production of peptidoglycan, inhibiting cell wall synthesis (select toxicity - no side effects to host cells because they lack peptidoglycan)
  2. binds to 70S ribosome, blocking protein synthesis
  3. interferes/alters bacterial cell membrane or LPS in Gram - outer membrane to
  4. inhibits DNA synthesis, blocking cell replication and transcription
  5. competes with bacterial metabolic enzymes, stopping synthesis of product (antimetabolite)
  6. interrupts ATP synthesis to reduce ATP production
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16
Q

Antibiotics and mechanism of action:

A
17
Q

What are the 3 targets of antibiotics that target cell wall biosynthesis? What drugs are in each category?

A
  1. transpeptidase/penicillin-binding proteins (PBPs) - β-lactams (Penicillins, Cephalosporins, Carbapenems, Monobactams)
  2. peptidoglycan subunits - glycopeptides (Vancomycin)
  3. peptidoglycan subunit transport - Bacitracin
18
Q

How was Penicillin discovered?

A

Alexander Fleming was doing research on Staphylococcus and left a plate on his bench over holiday - when he came back a fungus (Penicillin rubens) was growing on the plate and prevented Staphylococcus from growing near it

19
Q

What is structurally the same in all Penicillins?

A

β-lactam, a four-atom ring
(structure defines function)

20
Q

What are the 2 divisions of Penicillins based on spectrum?

A

NARROW SPECTRUM:
- natural penicillis: Penicillin G and V
- very narrow spectrum/anti-Staphylococcal: Methicillin, Oxacillin, Cloxacillin

BROAD SPECTRUM:
- extended spectrum: Ampicillin, Amoxicillin
- anti-pseudomonal: Carbenicillin, Ticarcillin, Piperacillin

21
Q

What 2 enzymes are responsible for the development of Penicillin resistance?

A
  1. penicillinase - inactivates Penicillin
  2. β-lactamase - produced by almost all Gram-negative bacteria and hydrolyzed the β-lactam ring of Penicillins and Cephalosporins
22
Q

What are the 3 β-lactamase inhibitors used as potentiated penicillins?

A
  1. clavulanic acid (Amox or Ticar)
  2. sulbactam (Amp)
  3. Tazobactam
23
Q

What are the 2 natural penicillins? What are their therapeutic uses? What bacteria do they work against?

A
  1. Penicillin G - treats infections in all species
  2. Penicillin V - used INFREQUENTLY for long-term oral therapy in dogs, cats, and horses

Gram + non-penicillinase-producing pathogens

24
Q

What are the 3 penicillin-resistant penicillins? What are their therapeutic uses? What bacteria do they work against?

A
  1. Methicillin
  2. Oxacillin
  3. Cloxacillin

treats against severe Staph infections, but less effective against Strep than natural penicillins

Gram +

25
Q

What are the main 2 groups of broad-spectrum penicillins? What are their therapeutic uses? What bacteria do they work against?

A
  1. Ampicillin, Amoxicillin - treats infection in all species
  2. Carbenicillin, Ticarcillin, Piperacillin - treat ear and skin infections in dogs caused by Pseudomonas spp.

Gram + and Gram -; not penicillinase stable

26
Q

Which penicillins are well-absorbed orally? Why?

A
  • Penicillin V
  • Ampicillin
  • Amoxicillin
  • Oxacillin
  • Cloxacillin
  • Carbenicillin

acid-stable against gastric acid

27
Q

Which penicillins are poorly absorbed orally? Why?

A
  • Penicillin G
  • Methicillin
  • Ticarcillin

broken down by gastric HCl

28
Q

What are the main 2 causes of penicillin resistance?

A
  1. inactivation of penicillins by penicillinases
  2. not binding to penicillin-binding proteins (PBPs)
29
Q

What is the most common adverse reaction in horses taking penicillins? Potassium penicillin? Procain G penicillin?

A

allergic reactions

cardiac arrhythmia (IV) in all species and diarrhea in horses

spontaneous abortion in cows

30
Q

When is Procaine G penicillin contraindicated?

A

birds, snakes, turtles, guinea pigs, chinchillas, or racehorses due to CNS effects

Veterinary Pharmacology (35 decks)

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