Session 10 - General summary

Question 1

Outline the structure of a virus

Answer 1

• Envelope surrounds
  
  • A protein coat which surrounds
  • Nucleic acid (DNA or RNA)

Question 2

What is the difference between the cell walls of gram negative and gram positive bacteria?

Answer 2

• Gram positive
		○ Plasma membrane
		○ Periplasmic space
		○ Peptidoglycan
	• Gram negative
		○ Plasma membrane
		○ Periplasmic space
		○ Petidoglycan
		○ Outer membrane (lipopolysaccharide and protein)

Question 3

Why are antivirals harder to develop than antibacterials?

Answer 3

• Have to target virus while avoiding damage to eukaryotic cells they live within

Question 4

What are the two types of fungi?

Answer 4

• Yeast - Single celled organism

* Multicellular

Question 5

What are the two types of parasites?

Answer 5

• Single celled - protozoa

* Multi-cellular

Question 6

What is a bacteriophage?

Answer 6

• Viruses which parasitise prokaryotic cells

* Can be used to treat bacterial infections

Question 7

What is pharmacokinetics when applied to antimicrobials?

Answer 7

• What the body does to the drug

Question 8

What is pharmacodynamics when applied to antimicrobials?

Answer 8

• What the drug does to the body

Question 9

How can you ensure pharmacokinetics doesn’t hinder drug effects (3)

Answer 9

• Right dose
  
  • Right frequency
  • Right duration

Question 10

What is the minimum inhibitory concentration?

Answer 10

• The minimum amount of an antibiotic required to inhibit the growth of the bacteria in vitro

Question 11

How can antibiotics be classified according to pharmacodynamics?

Answer 11

• Time dependent klling
○ Penicillin
○ Vancomycin
• Concentration dependent killing

Question 12

What is time dependent killing in an antibiotic?

Answer 12

• Succesful treatment required prolonged antibiotic presence at site of infection
  
  • Not high concentration

Question 13

What is concentration dependent killing in an antibiotic?

Answer 13

• Succesful treatment requires high antibiotic concentration at site of infection
  
  • Not for long
  • Very high C max

Question 14

What is therapeutic dug monitoring?

Answer 14

• Ensures adequate, non-toxic dose

Question 15

What is therapeutic drug monitoring used with

Answer 15

• Aminoglycosides including gentamicin

* Vancomycin

Question 16

Outline how you can measuree antibiotic activity

Answer 16

• Precise amount of placed on disc in petridish
  
  • Will halt growth of bacteria in zone around antibiotic
  • Measure size of zone of exclusion around antibiotics disc to ascertain resistance

Question 17

How do you measure MIC (minimum inhibitory concentration)? When is this useful?

Answer 17

• E test
  
  • Use strip on petri dish with varying concentrations of antibiotic infused along strip
  • Where bacteria intersects with disc, you have the MIC
  • Infective endocarditis, need to the right antibiotic

Question 18

What are the two ways in which bacteria gain antibiotic resistance?

Answer 18

• Chromosomal gene mutation -> Vertical gene transfer

* Horizontal gene transfer

Question 19

Give four different methods of antibiotic resistnace

Answer 19

• Alteraton of target site
  
  • Alteration of metabolic pathways
  • Reduced intracellular antibiotic accumulation
  • Antibiotic inactivation

Question 20

Give an example of a bacterial alteration of target site to become resistant

Answer 20

• Penicillin binding protein

Question 21

Give an example of the alteration of metabolic pathways

Answer 21

• Para-aminobenzoic acid is normally required by bacteria but some can use preformed folic acid instead

Question 22

Give two examples of reduced intra cellular antibiotic accumulation as a method of antibiotic accumulation

Answer 22

• Decrease permeability

* Active efflux mechanisms

Question 23

Give an example of antibiotic inactivation as a method of antibiotic resistance

Answer 23

• Antibiotic inavtivation

* Beta-lactamase

Question 24

Name three antibiotic resistant pathogens other than MRSA

Answer 24

• MDR-TB
  
  • Glycopeptide intermediate susceptibility staphylococcus aureus (GISA)
  • Glycopeptide Resistant enterococci - GRE

Question 25

What are the two main ways in which antibiotic resistance can be stopped?

Answer 25

• Prevent bacterial exposure to antibiotics

* Prevent the spread of recognised resistant bacteria

Question 26

Give two ways of preventing bacterial exposure to antibiotics

Answer 26

• Minimise risk of infection

* Monitor and control antibiotic prescribing

Question 27

Give three ways of preventing the spread of recognised resistant bacteria

Answer 27

• Isolation or cohorting
  
  • Hand hygiene
  • Decolonisation of patients