Antimicrobial by action groups

Question 1

Inhibition of cell wall synthesis

Answer 1

B lactase - penecillin

• binds to pencilian binding proteins
• stops cross linking
• triggers peptidoglycan breakdown = lysis
• can be broad spectrums and narrow spectrum (gram positive usually)

Glycoproteins (vancomycin)

• bind to D-alayl-Dalanine which is located on the peptidoglycan pentathlon peptide chain (preventing prospering bacterial binding to this site)
• often last line against s. aures

Bacitracin

• interferes with transport of peptidoglycan components through the cell membrane
• due to its toxicity it is primarily used in first aid ointments
• often used with polymixins

Question 2

Inhibit cell membrane function

Answer 2

Polymixins

• catatonic detergents binding to the phospholipids in the outer cell membrane (Gram -ve),= increase permeability + disrupts cell
• as it targets cell membranes, it is toxic to human so is used topically with bacitracin

Question 3

Inhibition of protein synthesis

Answer 3

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Aminoglyocosides

• 30s ribosome part = prevents translation of tRNA
• Toxic = nephrology and oto
• often used with B lactam drugs

Tetracyclines

• 30s ribosome reversibly bind, it prevents tRNA from bind to the Ribosome
• effective against gram + and -
• Toxicity = reduced bone growth, teeth staining in young animals, liver microsomal induction, oesophageal stricture (doxycycline)
• mycoplasma

Chloromphenicol

• 50s inhibits peptides from binding to each other
• toxicity - Aplastic anemia
• effective against wide range of organisms - spirochetes, rickettsia
• often a last resort drug

Macrolides + lincomycin

• 50s ribosomes reversibly bind = prevents protein synthesis
• effective against various gram + and mycoplasma
• drug choice in patients allergic to penicillin

Question 4

Inhibition of nucleic acid synthesis

Answer 4

Fluoroquinolones

• inhibits topoisomerase = no supercoiling of DNA
• gram + and gram -
• good reptiles + birds

Nitromidazoles

• binds to DNA and causes it to fragment
• anaerobes

Question 5

Synthesis of essential metabolies

Answer 5

Sulphonamides/trimethoprim

• -> blocks enzymes of folic acid synthesis
• toxicity = kerroconjuncitits sic and idiosyncratic hepatic toxicity dogs