Session 5

Question 1

What are the steps involved in the viral replication cycle?

Answer 1

1) Binding and adsorption of the virus to the host.
2) Virus endocytosed into the cell.
3) Viral RNA is synthesised and replicated to form new RNA.. Virus then assembled within the cell.
4) Virus is released by budding and then released from the cell.

Question 2

What are the two steps involved for uncoating and successful transcription of viral RNA?

Answer 2

1) ATP-driven entry into the endosome, allowing fusion of the viral membrane to the internal endosomal membrane.
2) Protons must enter the virus via an M2-ion channel. The subsequent fall in pH allows the viral coat of the nucleocapsid to breakdown.

Question 3

Which glycoprotein is required to prevent adhesion of viruses upon release?

Answer 3

Neuraminidase.

Question 4

Which type of influenza is the most serious and why?

Answer 4

Type A as they have multiple host species, and exhibit antigenic shift and drift.

Question 5

What are M2 ion channel blockers?

Answer 5

E.g. Amantadine and Ramantadine. They prevent entry of protons into the virus itself, via the M2 ion channels. Used to treat influenza A.

Question 6

Give two ADRs of M2 ion channel blockers.

Answer 6

Dizziness, GI disturbance, hypotension, confusion, insomnia, hallucinations.

Question 7

Describe the role of neuramidase inhibitors.

Answer 7

Block virion release from the host cell membrane, hence they are unable to infect other host cells. Used to treat influenza A and B.

Question 8

Give an example of a neuramidase inhibitor.

Answer 8

Zanamivir and Oseltamivir.

Question 9

Give 2 ADRs of neuramidase inhibitors.

Answer 9

Headache, nose bleed, respiratory depression, bronchospasm.

Question 10

Name the three antibiotic targets, and give an example of each.

Answer 10

DNA synthesis = Quinolones, e.g. Ciprofloxacin.
Protein synthesis = Aminoglycosides (Gentamicin), Macrolides (erythromycin) and Tetracyclines.
Cell wall synthesis = Beta-lactams (Penicillins, Cephalosporins and Carbapenems), Glycopeptides (Vancomycin).

Question 11

What are common ADRs or antibiotics?

Answer 11

Diarrhoea, fever, nausea, vomiting and immediate hypersensitivity reactions.

Question 12

Give the two mechanisms through which antibiotic resistance develops.

Answer 12

Intrinsic: due to gene mutation within the bacteria itself.
Extrinsic: resistance acquired from another bacterium passing on the information, e.g. via transformation, conjugation and transduction.

Question 13

What is the difference between transformation and transduction in terms of antibiotic resistance?

Answer 13

Transformation = uptake of naked DNA
Transduction = movement of genetic material by bacteriophages.

Question 14

What is conjugation?

Answer 14

cell-to-cell contact whereby chromosomal DNA is transferred from one bacterium to another, via plasmids.

Question 15

Give two effects of antibiotic resistance.

Answer 15

1) Antibiotic inactivation
2) Alteration of target site
3) Alteration of metabolic pathways
4) Reduced intracellular antibiotic accumulation

Question 16

Give two steps to avoid spread of resistance.

Answer 16

Antimicrobial stewardship,
Infection control,
Preventing spread of recognised resistant bacteria.

Question 17

What are the two major determinants of bacterial killing?

Answer 17

Time and concentration above the minimum inhibitory concentration.

Question 18

What is time-dependent killing?

Answer 18

Some antibiotics are effective due to the extensive amount of time the antibiotic binds to the microorganism, and how long they spend above the minimum inhibitory concentration.

Question 19

What is concentration-dependent killing?

Answer 19

Successful treatment requires high antibiotic concentration at the site of infection, but the exposure is not a long time. E.g. aminoglycosides or metronidazole.