Definitions

Question 1

Differential toxicity

Answer 1

Antibiotic needs to be more toxic to the infecting organism than the host

Question 2

Activity spectrum of an antibiotic

Answer 2

Qualitative measure of how many organisms the drug is effective against (broad or narrow spectrum)

Question 3

MIC

Answer 3

MInimum inhibitory concentration

Minimum concentration of antibiotic required to inhibit organism growth

Question 4

MBC

Answer 4

MInimum bactericidal concentration

Minimum concentration of an antibiotic required to kill the organism

Question 5

Bacteriostatic antibiotic

Answer 5

Inhibits organism growth (MIC

Question 6

Bactericidal antibiotic

Answer 6

Kills organism

MIC = MBC

Question 7

Concentration dependent antibiotic activity

Answer 7

Hgher drug concentration relative to MIC = greater rate and extent of antimicrobial activity

Question 8

Time-dependent antibiotic activity

Answer 8

Longer time span with drug at dose higher than MIC = greater rate and extent of antimicrobial activity

Question 9

Prophylactic antibiotic administration

Answer 9

Antibiotics given to prevent infection (eg before surgery)

Question 10

Treatment antibiotic administration

Answer 10

Antibiotics given to cure existing or suspected infection

Question 11

Therapeutic index

Answer 11

Toxic dose / Effective dose

Low TI: may require therapeutic drug monitoring (TDM) to ensure drug stays at maximally effective but not toxic levels

Question 12

Two examples of antibiotics that have a low TI

Answer 12

aminoglycosides, vancomycin

Question 13

8 characteristics of the ideal antibiotic

Answer 13

No/low toxicity to host
Low propensity for development of resistance
Does not induce hypersensitivities in host
Rapid and extensive tissue distribution
Long half life (less frequent dosing = increased compliance)
No interactions with other drugs
Convenient administration (multiple options?)
Inexpensive

Question 14

Empiric therapy

Answer 14

Broad spectrum treatment

Used when species is unknown, based on epidemiology of the area, disease severity, and local rates of resistance

Question 15

Advantages of combination therapy (4)

Answer 15

Empiric therapy before organism is identified
Useful for polymocrobial infections
Synergy
May prevent resistance

Question 16

Disadvantages of combination therapy (4)

Answer 16

Expensive
Increased risk of side effects or drug-drug interactions
Antagonism
Usually not necessary for maximal efficacy

Question 17

Things to consider when choosing an antibiotic to prescribe

Answer 17

Activity against organism
Acute vs chronic disease (reinfection vs recurrence)
Antibiotic history in the past 3 months
Site of infection
Mode of administration/toxicity/cost
Metabolism and excretion
Duration of treatment/frequency of dose
Local rates of resistance
Concomitant medications

Question 18

Mechanisms of gene transfer between bacteria

Answer 18

Transformation (picking up loose genetic material from destroyed cell)
Transduction (viral deposit of generic material)
Conjugation (transfer of plasmid from one bacterium to another via pilus)