Principles of Antimicrobial Therapy

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29 Terms

1
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What is an empiric antibiotic?

Covers ALL suspected pathogens based on infection type & specific patient factors

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What is a definitive antibiotic?

One that targets SPECIFIC microorganisms

3
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What is an antibiotic used for prophylaxis?

One that prevents infection (normally preoperative)

4
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What is narrow spectrum?

  • Acts on single or limited group of microorganisms
  • Example: Beta lactams target staph
5
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What is extended spectrum?

  • Structurally modified so it is more effective against a greater # of microorganisms
  • Example: Gram + and Gram - (amox → strep, staph, e.coli)
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What is broad spectrum?

  • Very wide spectrum and used empirically in severe infections
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What do broad spectrum abx have a risk of?

High risk of C.Diff infection

8
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Define bacteriostatic

Stops growth but does NOT kill bacteria; dependent on immune system

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Define Bacteriocidal

Kills the organism (must have 3 log kill w/in 24 hrs); independent of immune system

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What are examples of Bacteriostatic abx?

  • Clindamycin
  • Macrolides (clarithro, erythro, azithro)
  • Tetracyclines (cyclines)
    "Country Music Television"
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What are examples of Bacteriocidal abx?

  • Aminoglycosides (tobra, genta)
  • Beta Lactams (cillins, cephalosporins, carbapenems)
  • Quinolones (floxacins)
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What are the possible results of abx combo therapy?

  • Indifference: adding the second drug doesn't create a significantly different effect
  • Synergy: adding the second drug creates a significantly improved effect
  • Antagonism: adding the second drug reduces the overall efficacy of the drug therapy
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What antimicrobials inhibit cell wall synthesis?

  • Beta Lactams (penicillins, cephalosporins, carbapenems, monobactams)
  • Vancomycin
  • Bacitracin
  • Polymyxins
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What antimicrobials inhibit nucleic acid synthesis?

  • Sulfonamides
  • Trimethoprim
  • Quinolones
  • Rifampin
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What antimicrobials inhibit protein synthesis?

  • Macrolides
  • Clindamycin
  • Linezolid
  • Chloramphenicol
  • Streptogramins
  • Tetracyclines
  • Aminoglycosides
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What are the 7 factors to consider when initiating antimicrobial therapy?

  1. Site of infection
  2. Usual causative pathogens
  3. Antimicrobial resistance (Use antibiogram → want susceptibility >90)
  4. Identity & drug sensitivity of organism
    (Minimum Inhibitory Concentration (MIC))
  5. Bacterial vs bacteriostatic effect of drug
  6. Safety, cost, drug formulary
  7. Patient specific factors
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What is an example of considering site of infection when choosing abx?

For meningitis, give drug that crosses BBB

18
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What is an example of considering usual causative pathogens when choosing abx?

For CAP, give drug that covers Strep pneumo, etc

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What are patient specific factors to consider when choosing abx?

  • Status of host defenses/immune fxn
  • Pharmacogenetics
  • Renal/hepatic fxn
  • Perfusion status
  • Drug allergies/drug interactions
  • Pregnancy/lactation
20
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What is time dependent drug dosing?

Bacterial kill rate improves the longer the concentration is above MIC

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What is an example of time dependent drug dosing?

Beta lactams which need multiple doses over shorter periods

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What is concentration dependent drug dosing?

Bacterial kill rate improves w/ higher concentrations above MIC

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What is an example of concentration dependent drug dosing?

Aminoglycosides which need higher concentration peak for greater post abx effect

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For what drug is AUC/MIC important?

Vancomycin

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Do gram - organisms have a thick or thin cell wall?

Thin

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Do gram + organisms have a thick or thin cell wall?

Thick

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Do gram + or gram - bacterial have an outer membrane?

Gram -

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What do acid-fast bacteria have?

Mycolic acids

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What is post antibiotic effect (PAE)?

Continued suppression of the drug when the concentration drops below the MIC