Antimicrobials II

Question 1

Isoniazid: MOA, resistance

Answer 1

• Inhibits InhA in mycolic acid biosynthesis
• Prodrug- mutations in several genes bactercidal

Question 2

Rifampin: MOA, resistance

Answer 2

• Inhibits transcription by binding to the RNA polymerase
• Mutations in RNAP bactercidal

Question 3

Ethambutol: MOA, resistance

Answer 3

• Inhibits arabinosyl transferases in cell wall biosynthesis
• Mutations in EMB genes Static (cidal in MAC?)

Question 4

Pyrazinamide: MOA, resistance

Answer 4

• Depletes energy reserves of cell-membrane effects
• Prodrug- PCNA gene Better in acidic env. bactercidal

Question 5

Streptomycin: MOA, resistance

Answer 5

• Protein synthesis inhibition 30S ribosomal subunit bactericidal

Question 6

Isoniazid: pharmacokinetics

Answer 6

• Orally available Well distributed Metabolized- I in CRIMES
• Acetylation rates differ

Question 7

Rifampin: pharm

Answer 7

• Orally available Well distributed – colors fluids orange Metabolized- R in CRIMES
• Potent inducer of CYP450s

Question 8

Ethambutol: pharm

Answer 8

• Orally available Well distributed; lungs CSF
• Renal excretion

Question 9

Pyrazinamide: pharm

Answer 9

• Orally available Well distributed; lungs CSF
• Renal excretion

Question 10

Streptomycin: pharm

Answer 10

• Poor oral abs.(IV/IM)
• distr. to TBW accum. in kidney, ear
• Renal excretion

Question 11

Isoniazid: adverse rxns

Answer 11

• Low/Medium
• Vit B6 deficiency-neuritis
• Hepatic damage (acetylator status important)
• EtOH

Question 12

Rifampin:adverse rxns

Answer 12

• Low/Medium
• Hepatic damage
• Drug interactions; HIV, steroids, etc….

Question 13

Ethambutol: adverse rxn

Answer 13

• Low/Medium
• Optic neuritis
• not for children (< 6) or in pregnancy
• Gout

Question 14

Pyrazinamide: adverse rxns

Answer 14

• Medium/high
• Hepatic damage – monitor SGOT levels
• Gout
• Not in pregnancy (US)

Question 15

Streptomycin: adverse rxns

Answer 15

• High toxicity
• Vestibular and auditory toxicity
• nephrotoxicity

Question 16

Isoniazid: sprectrum/uses

Answer 16

• Mycobacteria only (TB and M.Ka.)
• Intracellular activity

Question 17

Rifampin: sprectrum/uses

Answer 17

• Mycobacteria and Gram +ve
• Intracellular activity
• TB, endocarditis
• H. flu meningitis prophylaxis

Question 18

Ethambutol: sprectrum/uses

Answer 18

• Mycobacteria only (TB, M.Ka, MAC)
• Intracellular activity

Question 19

Pyrazinamide: spectrum/uses

Answer 19

• Mycobacteria only
• Semi-dormant bacteria in caseous lesions (acidic environment)
• Variable modest intracellular activity

Question 20

Streptomycin: spectrum/uses

Answer 20

• Med. Spectrum Gram – aerobes (E. coli, Pseudomonas)
• limited +
• TB – alternative 1st line treatment
• Not intracellular