Antibacterial Agents I - II

Question 1

antimicrobial mechanisms of action

Answer 1

1) targets
2) selective toxicity
3) resistance
- –natural (intrinsic) resistance
- –escape
- –acquired reistance
4) bactericidal (organisms are killed)
5) bacteriostatic agents (organisms are prevented from growing)

Question 2

Bactericidal mechanisms

Answer 2

• inhibition of cell wall synthesis
• disruption of cell membrane function
• interference with DNA function of synthesis

Question 3

Bacteriostatic mechanisms:

Answer 3

• inhibition of protein synthesis (exception: aminoglycosides, which are -cidal)
• inhibition of intermediary metabolic pathways

Question 4

Advantages of bactericidal agents

Answer 4

• Bactericidal agent preferred in severe infections (assuming sensitive organism, drug distribution, and drug safety are compatible).
• Bactericidal agents act more quickly and their action is often irreversible with a sustained effect after the drug is eliminated from the blood.
• Bactericidal agents can compensate for patients with an impaired host defense (diabetes, agammaglobulinemia, immunosuppressive drugs, AIDS, asplenia).
• Bactericidal agents are required for treatment of infections in locations that are not accessible to host immune system responses (e.g., endocarditic vegetations and cerebrospinal fluid).

Question 5

Important pharmacokinetic and host factors in selection of antimicrobial therapy:

Answer 5

1) Absorption. Provides information on the route of administration necessary for anti-infective effectiveness of the antibiotic.
2) Distribution. Once an antibiotic has been absorbed into the systemic circulation it must be distributed in sufficient concentration to the site of infection to be effective.
3) Elimination. Knowledge of the route of antibiotic elimination is critical to the safe and effective use of antibiotics and at a minimum, one should know the major organ of elimination for antibiotics, either the kidneys or the liver.
4) Duration of Antimicrobial Activity. Knowledge of the half-life of an antibiotic provides information regarding how often the drug will have to be administered to maintain the antimicrobial effect. Renal excretion and hepatic metabolism are the primary biologic processes that determine the plasma half-life of an antibiotic and the time that plasma levels remain above the MIC for a particular organism (its duration of action).