Antibiotics and Antibiotic resistance

Question 1

Define Antibiotic

Answer 1

A substance produced by a micro-organism (or a similar substance produced wholly or partly by chemical synthesis) which at low concentrations kills or inhibits the growth of other micro-organisms

Question 2

How are Antibiotics normally taken?

Answer 2

Used Systemically, meaning inside the body

Question 3

Define Selective Toxicity

Answer 3

Affects only the microbe

Affects the microbe much more than patient

Question 4

Define Bactericidal (C)

Answer 4

Kills and/or lyses bacterial cell

Question 5

Define Bacteriostatic (S)

Answer 5

Inhibits growth -reversible effect

Question 6

What are the targets for Antibiotics?

Answer 6

METABOLIC REACTIONS
CELL WALL
CELL MEMBRANE

Question 7

Why can target sites of the Antibiotics be a problem?

Answer 7

Besides the Cell wall, all of the targets are in the host as well as the microbe

Question 8

How does Sulphonamides (S) antibiotic effect the cell?

Answer 8

By inhibiting Folate metabolism

Question 9

How does Fluoroquinolones(C) antibiotic effect the cell?

Answer 9

By inhibiting DNA synthesis causing cell death

Question 10

How does Rifampicin (C) antibiotic effect the cell?

Answer 10

By inhibiting RNA synthesis (transcription), causing cell death

Question 11

How do Tetracyclines(S) and Chloramphenicol (S) antibiotic effect the cell?

Answer 11

By inhibiting Protein synthesis (translation)

Question 12

In the cell wall what are the two processes that Antibiotics target and what Antibiotics target these?

Answer 12

Synthesis
•Cycloserines(S)

Stability / integrity
•ß-lactams (C)
•Vancomycin(C)

Question 13

In the Cell Membrane, what are the two processes that Antibiotics target and what Antibiotics target these?

Answer 13

Stability / integrity
•Polymyxins(C)
•Polyenes(C)

Question 14

What is the difference between Folate metabolism in bacteria and in Mammalian cells?

Answer 14

Bacteria synthesise folic acid whereas humans obtain folic acid from diet

Question 15

How does Sulphonamides affect Folate Metabolism?

Answer 15

It inhibits the enzyme which activates the process between Para-Aminobenzoic acid and Dihydrofolic acid, preventing the conversion

Question 16

How does Trimethoprim affect Folate Metabolism?

Answer 16

It inhibits the enzyme which activates the process between Dihydrofolic acid and Trimethoprim, preventing the conversion

Question 17

How is Bacterial DNA coiled?

Answer 17

Activating gyrase

Question 18

Define Anti-gyrase

Answer 18

The process in which super-coiling in bacterial DNA is prevented

Question 19

What does Rifampicin do in the bacterial cell?

Answer 19

Prevents production of mRNAInhibits transcription

Question 20

How does Tetracycline Inhibit protein synthesis (translation)?

Answer 20

By acting on the 30s ribosome unit

Question 21

How does Chloramphenicol Inhibit protein synthesis (translation)?

Answer 21

By acting on 50s ribosome unit

Question 22

Define ß-LACTAMS

Answer 22

This is a group of Antibiotics which within their chemical structures contain a ß-Lactam ring.

Includes Penicillins and cephalosporins

Question 23

What does B-Lactams do?

Answer 23

Inhibit final stage of peptidoglycan assembly (cross-linking)

Bind irreversibly to transpeptidase

Induce autolytic enzymes

Question 24

In B-Lactams what does the R group do?

Answer 24

Gives properties such as acid resistance, membrane transport or resistance to ß-lactamase

Question 25

What is the Role of Vancomycin?

Answer 25

Binds to D-Ala-D-Ala on peptidoglycan side chain

Block transpeptidation

Question 26

What is the role of Polymyxin

Answer 26

Disrupts bacterial cell membranes

Question 27

Why are Antifungal drugs hard to produce?

Answer 27

Fungi are eukaryotes with similar structure function to humans & animals.

Harder to find unique targets

Difficult to treat

Question 28

Why are Anti viral drugs hard to produce?

Answer 28

• Viruses use the host cells own metabolic processes to replicate
• Even harder to treat as the target is the host.

Question 29

What is the problem with Nucleoside analogues and give examples

Answer 29

Toxic to host too

Ganciclovir

Zidovudine(AZT)

Question 30

What is the two different Antibiotic resistance?

Answer 30

Natural/Innate Resistance and Acquired Resistance

Question 31

Define Natural/Innate Resistance

Answer 31

Variations in the structure of cell envelope/cell wall

Altered binding sites/enzymatic inactivation

Efflux mechanism

Question 32

Define Acquired Resistance

Answer 32

Mutation

Adaptation

Gene Transfer (plasmids, transposons)

Question 33

Where the Genes that are responsible for Antibiotic Resistance located?

Answer 33

Chromosome or on plasmid

Question 34

Define Exclusion

Answer 34

Envelope impervious to antibiotic

Gram-negative bacterial Outer Membrane

Question 35

Define Excretion

Answer 35

Tetracycline efflux pump, removal of Tetracycline

Question 36

Define Alter targets

Answer 36

Structure of ribosome (methylation of ribosomal RNA), polymerases and gyrases

Modify metabolic pathway -sulphonamides

Question 37

Define Destroy antibiotic

Answer 37

B-lactamases open B-lactam ring

Question 38

Define Modify antibiotic

Answer 38

–Phosphorylation -Streptomycin

–Acetylation –Chloramphenicol

Question 39

What are the causes of Antibiotic Resistance?

Answer 39

• Over-prescribing
• Non-compliance
• Indiscriminate use of antibiotics e.g supplement feeds in agriculture

Question 40

What ways can we overcome Antibiotic resistance?

Answer 40

• Identification of the pathogen
• Selection of the antimicrobial agent appropriate for the pathogen
• Is the organism resistant to the prescribed antibiotic
• Drug combinations (penicillin + clavulanic acid)