LG 7.5 - Into to Antimicrobials

Question 1

Define “selective toxicity” when referring to microbial cells and human cells.

Answer 1

• Microbes can have structures and/or processes that human cells do not have.
• Antimicrobial “selective toxicity” refers to the ability of these drugs to kill or inhibit the growth of microbes, leaving the human host unharmed.
• “selects to kill microbes, leaves us unharmed”

Question 2

What are the mechanisms of bacterial resistance to antimicrobial agents?

Answer 2

1) Drug does not reach its target (permeability, porin channel mutation, efflux pumps).
2) Drug is inactivated (enzymes, for example beta-lactamases).
3) Target or biochemical pathway is altered so drug cannot bind and/or act.

Question 3

What are some strategies that have been discussed to improve antibiotic utilization (i.e. what are the components of an Antimicrobial Stewardship)?

Answer 3

• Formulary restriction and preauthorization (1 of 2 core strategies)
• Prospective audit with intervention and feedback (2 of 2 core strategies)
• Standardized order sets and clinical pathways (foster evidence-based prescribing).
• Antimicrobial order forms.
• De-escalation of therapy (more to come on this, next flashcard).
• Dose optimization (right dose for site of infection; renal dose adjustment; pk/pd applications).
• Intravenous (IV) to oral dose conversion.

Question 4

What is de-escalation of antimicrobial therapy, what is this process?

Answer 4

• Monitoring of therapy.
• Cultures and initial antimicrobial treatment regimen are utilized.
• Follow up regimen is then used.
• This is then used to analyze next step, de-escalation:
  1) discontinue antimicrobial(s)
  2) switch to more focused therapy based on culture/sensitivity (C&S) results.
  3) change to oral antimicrobial(s)

Question 5

What is an antibiogram, what is it used for?

Answer 5

• LOCAL summary of selected antibiotic activity versus common bacterial isolates.
• Used for drug formulary decisions and to guide empiric treatment.

(Do question from slide 42 + 43, to help with interpretation of these tests).

Question 6

Regarding antibiotics what do the terms “-cidal” and “-static” mean?

Answer 6

• cidal = kill

- static = stop growth

Question 7

What does MIC and MBC stand for?

Answer 7

• MIC = minimal inhibitory concentration. (minimum concentration of drug needed to inhibit growth).
• MBC = minimal bactericidal concentration.

Question 8

What is synergy regarding antimicrobial drugs?

Answer 8

• Using two drugs together causes a greater effect than either drug by themselves or the estimated combination effect.

Question 9

What is antagonism between two antimicrobials?

Answer 9

• Using 2 drugs together, one drug drops the efficacy of the other.