Antimicrobials [17-18]

Question 1

What is selective toxicity

Answer 1

Using antibiotics to exploit difference in processes & structures of pro/eukaryotes to reduce host cell toxicity
E.g cell wall

Question 2

2 types of antibiotic

Answer 2

Bacteriostatic (inhibit multiplication)
Bactericidal

Question 3

What do antibiotics target in bacteria

Answer 3

Cell wall synthesis
Membrane synthesis
Protein synthesis
Metabolic pathways
Nucleic acid synthesis

Question 4

Is cell wall thicker in gram positive or gram negative

Answer 4

Gram positive

Question 5

Explain crosslinking

Answer 5

Transpeptidase links L-lys D-ala D-ala residues from different cell walls

Question 6

Penicillin MOA

Answer 6

Binds to transpeptidase so it can inhibit cross linking

Question 7

Example of 4 b-lactams

Answer 7

Penicillin
Cephalosporin
Monobactam
Carbapenem

Question 8

What is flucloxacillin

Answer 8

Beta lactamase resistant penicillin
Acts of gram positive
Gram positive are more reliant on cross linking because they have a larger cell wall

Question 9

What is a good all rounded penicillin

Answer 9

Amoxicillin - broad spectrum pencilling
For gram positive and negative

Question 10

Describe cephalosporins

Answer 10

Beta lactam ring
Bind to penicillin binding protein
Prevents cross linking
Treats pneumonia and meningitis
Can cause diarrhoea

Question 11

What is given in the case of a penicillin allergy

Answer 11

Monobactams
B lactam ring is peripheral
Beta lactamase resistant
Against gram neg

Question 12

Mechanisms of penicillin resistance

Answer 12

Porin downregulation
Inactivation of antibiotic via enzymes
Production of efflux pumps to pump antibiotics out of cell
Target site modification
Production of beta lactamase
Modification of penicillin-binding proteins

Question 13

Explain penicillin allergy

Answer 13

Antigens are degradation products of penicillin
Rash
Itching
Could cause anaphylactic shock
Lack of consciousness

Question 14

4 antibiotics that inhibit protein synthesis

Answer 14

Streptomycin
Chloramphenicol
Erythromycin
Tetracyclines

Question 15

Streptomycin MOA

Answer 15

Changes shape of 30s portion of ribosome
mRNA code read incorrectly

Question 16

Chloramphenicol MOA

Answer 16

Binds 50s portion of ribosome
Inhibits peptide bond formation

Question 17

Erythromycin MOA

Answer 17

Binds to 50s portion of ribosome
Prevents translocation of ribosome along mRNA

Question 18

Tetracyclines MOA

Answer 18

Interfere with attachment of tRNA to mRNA-ribosome complex
Competitively binds A site
- Chlamydia
Resistance a growing problem

Question 19

What drug class is is streptomycin

Answer 19

Aminoglycoside

Question 20

Which antibiotics activity is enhanced by penicillins

Answer 20

Aminoglycosides

Question 21

What drug class is erythromycin

Answer 21

Macrolide

Question 22

Macrolides pharmacokinetics & adverse effects

Answer 22

Oral - enteric coated
Most effective against gram positive
Metabolised by CYP3A4
Resistance - efflux or methylation of ribosomal targets
Heart arrhythmias
GI disturbance

Question 23

Chloramphenicol pharmacokinetics & adverse effects

Answer 23

Oral / IV
Resistance - enzymatic inactivation by acetyltransferase, efflux, ribosomal mutations
Grey baby syndrome

Question 24

What is folate

Answer 24

Made from PABA - component in DNA synthesis

Question 25

What inhibits conversion of PABA to folate

Answer 25

Sulfonamides

Question 26

What inhibits folate utilisation

Answer 26

Trimethoprim

Question 27

Sulphonamide PK

Answer 27

Crosses BBB
N-acetylated in liver

Question 28

Trimethoprim most common use

Answer 28

UTI and respiratory tract infection

Question 29

What do fluoroquinolones do

Answer 29

Inhibit DNA gyrase
Blocks DNA supercoiling

Question 30

Fluroquinolones PK

Answer 30

Oral
Crosses BBB
gram +ve and -ve
Inhibits CYP1A2
Affects GI

Question 31

Examples of mycobacteria and

Answer 31

Mycobacterium tuberculosis
Mycobacterium leprae

Question 32

Mycobacteria traits

Answer 32

Thick waxy lipid-rich hydrophobic cell walls
Contain mycolic acids in cell wall
Can survive in macrophages
Becoming a major problem in immunocompromised patients

Question 33

2 mycobacterium treatments

Answer 33

Rifampicin
Daptomycin

Question 34

Rifampicin traits

Answer 34

Derivative of Rifamycin
Inhibits prokaryotic DNA dependent RNA polymerase
Good against +ve -ve and mycobacteria
Potent inducer of CYP3A4

Question 35

4 forms of antibiotic resistance

Answer 35

Modified permeability - porin substitution
Drug inactivation - beta lactamases
Interaction prevention - modified penicillin binding proteins
Drug conc regulation - efflux

Question 36

3 methods of acquiring resistance

Answer 36

Transformation
Transduction
Conjugation

Question 37

What is transformation

Answer 37

Transfer of free DNA (containing antibiotic resistant gene) to competent recipient cell (can take up DNA)

Question 38

What is transduction

Answer 38

Transfer of bacteria DNA containing antibiotic resistance gene via bacteriophage

Question 39

What is conjugation

Answer 39

Plasmids transferred by conjugation
Direct contact between cells
Doesn’t require bacteria to be the same species

Question 40

How can we tackle antibiotic resistance

Answer 40

Improve public awareness
Reduced inappropriate antibiotic use
Invest in drug R&D
Reduce use of broad spectrum antibiotics in livestock