Antibiotics Symposium: Principles of Antibiotics

Question 1

What is an antibiotic?

Answer 1

agents produced by micro-organisms that kill or inhibit the growth of other micro-organisms in high-dilution

Question 2

How much bacteria is killed in 18-24 hours by bacteriostatic antibiotics?

Answer 2

> 90%

Question 3

What are antibiotics defined as being a ratio of?

Answer 3

a ratio of Minimum Bactericidal Concentration (MBC) to Minimum inhibitory Concentration (MIC) of > 4

Question 4

What may happen to Minimum inhibitory Concentration (MIC) in resistance?

Answer 4

May increase

Question 5

What do antimicrobials do?

Answer 5

molecules that work by binding a target site on a bacterium

Question 6

What are the 2 major determinants of anti bacterial effects?

Answer 6

The two major determinants of anti bacterial effects are the concentration and the time that the antibiotic remains on these binding sites

Question 7

What is time dependent killing?

Answer 7

• Key parameter is the time that serum concentrations remain above the MIC during the dosing interval:
• t>MIC

Question 8

What is concentration dependent killing?

Answer 8

• Key parameter is how high the concentration is above MIC
• peak concentration/MIC ratio

Question 9

What are defined as points of biochemical reaction crucial to the survival of the bacterium?

Answer 9

o Penicillin-binding proteins in cell wall
o Cell membrane
o DNA
o Ribosomes
o Topoisomerase IV or DNA gyrase
- can be targeted by antimicrobials

Question 10

How do bacteria resist antibiotics?

Answer 10

• Change antibiotic target
• Destroy antibiotic
• Prevent antibiotic access
• Remove antibiotic from bacteria

Question 11

What are the 2 types of bacterial resistance?

Answer 11

Intrinsic
Acquired

Question 12

Describe intrinsic resistance

Answer 12

All subpopulations of a species will be equally resistant

Question 13

Describe acquired resistance

Answer 13

• A bacterium which was previously susceptible obtains the ability to resist the activity of a particular antibiotic
• Only certain strains or subpopulations of a species will be resistant

Question 14

What are 2 examples of gram positive bacteria that are resistant?

Answer 14

• MRSA (Methicillin resistant Staphylococcus aureus)
• VRE (vancomycin-resistant enterococci)

Question 15

What are 2 examples of gram negative bacteria that are resistant?

Answer 15

• ESBL (extended spectrum beta lactamase (ESBL) inhibition)
• AmpC b-lactamase resistance (Broad spectrum penicillin, cephalosporin and monobactam resistance)