Antibiotics

Question 1

What is an antibiotic?

Answer 1

Chemicals produced by microorganisms or plants that inhibit the growth of, and/or kill bacteria

Question 2

What is an antimicrobial?

Answer 2

An all encompassing term for all compounds which are active against one type of microbe, including:

• antivirals
• antibiotics
• antifungals
• antimalarials

Question 3

What reasons can antibiotics be used for?

Answer 3

• treatment of bacterial infection

- prophylaxis to prevent bacterial infection (e.g pre/post surgery, contacts in outbreaks)

Question 4

What are the targets from antibacterial action?

Answer 4

• cell wall synthesis inhibitors
• cell membrane
• nucleic acid synthesis
• protein synthesis

Question 5

Are antibiotics specific for bacteria?

Answer 5

Not all

Some may share targets present in other eukaryotes and therefore we try to find antibacterial with selective toxicity

Question 6

What is selective toxicity?

Answer 6

Ability of a drug to target sites relative to a specific organism and not cause side effects in the host

Question 7

What are the classes of antibiotics in clinical use?

Answer 7

• Beta lactams
• glycopeptides
• aminoglycosides
• tetracyclines
• chloramphenicol
• macrolides

Question 8

How do you decide which antibiotic to use?

Answer 8

Effectiveness is an interplay between patient, infecting organism and drug:

– Clinical evaluation :
• Typical pathogen for that site 
• Agents proven to be effective for that infection 
– Laboratory evaluation:
• Isolation of pathogen 
• Susceptibility of pathogen

Question 9

How do we determine susceptibility of an antibiotic?

Answer 9

Disc susceptibility

E-test

Question 10

What is the MIC?

Answer 10

• minimum inhibitory conc

- dilution of a drug that inhibits growth

Question 11

What factors limit antimicrobial efficacy?

Answer 11

• speed of action
• sensitivity of target
• adverse events

Question 12

What is the breakpoint concentration?

Answer 12

the concentration below which bacteria are classes as susceptible

Question 13

What are the three different outcomes for treating an illness with multiple antibiotics?

Answer 13

• synergy (greater effect when combined)
• antagonism (less of an effect when combined)
• indifference (no increase or decrease of an effect when combined)

Question 14

What are the pharmokinetics of antibacterial action?

Answer 14

• serum conc over time

- penetration to site of infection

Question 15

What are the pharmacodynamics of antibacterial action?

Answer 15

• susceptibility/potency of a drug
• concentration/time dependent killing
• PAE (post antibiotic effect)

Question 16

What routes can you give antibiotics?

Answer 16

• topical
• oral
• intravenous
• intramuscular

Question 17

How do you choose the route and dosage of antibiotics?

Answer 17

using the PK properties of each drug and adverse reactions to decide

Question 18

What are the differences between antibiotics and vaccines?

Answer 18

Antibiotics:
Specificity - usually high
Toxicity - potentially high
Duration of effect - usually short
Duration of treatment - may be prolonged
Effectiveness - high

Vaccine:
Specificity - very high
Toxicity - usually Low
Duration of effect - Usually low
Duration of treatment - Usually short/may need a booster
Effectiveness - Low-moderate

Question 19

How does antibiotic resistance arise?

Answer 19

-mutations in chromosomal genes (clonal spread of resistant organism)

-acquisition of foreign DNA e.g plasmids this can be caused by:
The spread of a resistant organism
Transfer of plasmids to new strains/species
Mutation in and/or recombination of genetic material

Question 20

What are the results of antibiotic resistance?

Answer 20

• 120,000 addition surgical site infections and infections after chemotherapy
• 6300 infection related deaths
• longer time to recover from infection
• some drugs no longer effective
• some surgeries/cancer treatments no longer viable due to risk of infection

Question 21

What happened in the 2011 global call for action?

Answer 21

antibiotic resistance must be seen as a global crisis akin to AIDs appropriate measures must be taken to reduce impacts in a ll areas of human activity