Aminoglycosides

Question 1

Spectrum

Answer 1

1. Gram negative aerobic
   i. fastidious: pasturella,haemophilus,mannheimia and actinobacillus
   ii. bordetella bronchiseptica
   iii. enterobactericae: E.coli, salmonella, klebsiella
   iv. proteus
   v. leptospira
2. Staphyloccocus (NOT on strep)
3. mainly used in Mycobacterium, Pseudomonas and Mycoplasma

Question 2

Biochemistry

Answer 2

6 amino groups- high NH2 can protonate easily , accumilate around negative charge -> ototoxic and nephrotoxic SE
•Spectinomycin is not a glycoside bond it is aminocyclitol.
• Neomycin (natural)
• Gentamicin (synthetic)

Question 3

Mechanism of action

Answer 3

• post-antibiotic effect
• CONCENTRATION dependent *bacteriocidal (except for spectinomycin
• produce false proteins at 30S unit, uptake with active transport -> O2 dependent (doesn’t kill anerobes)

Question 4

Resistance

Answer 4

• Ab ovo resistance
• Spreading by PLASMIDS
• Altering enzymes(periplasmic space→ acetylation, adenylation)
• Reduced permeability due to active transport (O2)
• Cross-resistance!!

Question 5

Pharmacokinetics

Answer 5

• accumilation
• hydrophylic
• kidney excretion
• Withdrawal period is extremely high
• Neomycin is most toxic (max. one week) and Spectinomycin is least toxic (3w)

Question 6

Drugs

Answer 6

1. Spectinomycin: BACTERIOSTATIC
   used in combination with penicillin (strep,mycoplasma)/ LINCOMYCIN
   2.Neomycin : PO,topical mastitis, combined in life threatening cases.
2. Gentamycin: PO,parenteral,topical
   Combine with amoxicillin clavulanic acid
   4.Amikacin: 2w, very active , slightly toxic , IV