Antimicrobials-Intro

Question 1

Antimicrobial

Answer 1

Any substance that kills or inhibits the growth of a microorganism, but causes little or no host damage

Question 2

Antibiotic

Answer 2

A substance produced by a microorganism that at low conc inhibits or kills other microorganisms

Question 3

Bacteriostatic vs Bacteriocidal

Answer 3

-Static: stops from dividing
-Cidal: Kills off
All are static at low concentrations, some are static at all concentrations

Question 4

Minimum inhibitory concentration (MIC)

Answer 4

Lowest concentration of a drug required to inhibit visible growth of bacteria in a test tube

Question 5

Minimum bactericidal concentration (MBC)

Answer 5

Minimum conc that kill >99.9% of the bacterium used in the MIC testing

Question 6

Breakpoint MIC

Answer 6

Value above which plasma concentrations are unlikely to be achieved and thus clinical benefit is unlikely with labeled dosing regimens.
Drug and host dependent (based on PK/PD)

Question 7

T > MIC

Answer 7

Time over MIC
cumulative % of a 24 hr period that drug concentration exceeds the MIC of the pathogen

Question 8

Cmax

Answer 8

Peak serum concentration

Question 9

Postantibiotic Effect (PAE)

Answer 9

Persistant inhibition of bacterial growth by an antimicrobial agent even when drug levels become below its MIC

Question 10

Dosing strategies

Answer 10

Optimize Cmax: Higher dose, less frequently
Lowest trough: high dose, less freq.
Highest AUC: equivalent
T>MIC: lower dose, more freq
Minimize Cmax: lower dose, more freq

Question 11

Four indications for the use of antimicrobial combinations

Answer 11

1. Synergism
2. Polymicrobial infections
3. Decrease the emergence of resistant isolates
4. Decrease dose-related toxicity

Question 12

How do you choose an antibiotic emprirically?

Answer 12

1. likely identity of the organism at a given site of infection
2. knowledge of the usual susceptibility profile
3. drug conc at site of infection
4. drug tox
5. cost of treatment
6. regulations/withdrawal times