Antibiotics - Chloramphenicol

Question 1

What is transcription?

1 - copying of specific part of DNA to create mRNA
2 - converting mRNA into proteins using the ribosome
3 - adding molecules to proteins
4 - packaging proteins into vesicles

Answer 1

1 - copying of specific part of DNA to create mRNA

Question 2

What is translation (also called protein synthesis)?

1 - copying of specific part of DNA to create mRNA
2 - converting mRNA into proteins using the ribosome
3 - adding molecules to proteins
4 - packaging proteins into vesicles

Answer 2

2 - converting mRNA into proteins using the ribosome

Question 3

Ribosomes in prokaryotes (bacteria) is smaller in eukaryotes (human cells). Why is this important for drug development?

1 - means bacteria are limited to how they replicate
2 - drugs can inhibit mRNA
3 - drugs can be targeted against prokaryotes ribosome specifically
4 - bacterial wall production can be inhibited

Answer 3

3 - drugs can be targeted against prokaryotes ribosome specifically

• prokaryotes - 50 and 30S = 70S
• eukaryotes - 60 and 40S = 80S

Question 4

Which of the following is NOT a step in translation (protein synthesis)?

1 - elongation
2 - transcription
3 - initiation
4 - termination

Answer 4

2 - transcription

Question 5

Which of the following described initiation?

1 - codon signalling termination is recognised by P site
2 - 1st tRNA binds to P site and begins adding further tRNA
3 - 50S and 30S subunits bind to mRNA forming ribosome-mRNA complex
4 - tRNA bind to the A, P and E binding sites of ribosome

Answer 5

3 - 50S and 30S subunits bind to mRNA forming ribosome-mRNA complex

• mRNA is the blueprint for protein synthesis
• composed of 3 nucleotide sequences called codons
• tRNA binds to codons with matching anti-codon sequence

Question 6

The ribosome complex has 3 specific sites where the mRNA can bind. Which of the following is NOT one of these sites?

1 - A site (aminoacyl site)
2 - B site (binding site)
3 - P site (peptidyl site)
4 - E site (exit site)

Answer 6

2 - B site (binding site)

• correct codons are added at sites A and P, building a protein, once finished a stop codon is recognised and the mRNA is then detached and a protein is formed.

Question 7

The ribosome complex has 3 specific sites where the mRNA can bind, A site (aminoacyl site), P site (peptidyl site) and E site (exit site). Once the correct codons have been added at site A and P, the mRNA is then detached and a protein is formed.

Question 8

Which of the following described elongation?

1 - codon signalling termination is recognised by P site
2 - 1st tRNA binds to P site and begins adding further tRNA at site A
3 - 50S and 30S subunits bind to mRNA forming ribosome-mRNA complex
4 - tRNA bind to the A, P and E binding sites of ribosome

Answer 8

2 - 1st tRNA binds to P site and begins adding further tRNA at site A

• this repeats until protein is finished

Question 9

Which of the following described elongation?

1 - codon signalling termination is recognised by P site
2 - 1st tRNA binds to P site and begins adding further tRNA at site A
3 - 50S and 30S subunits bind to mRNA forming ribosome-mRNA complex
4 - tRNA bind to the A, P and E binding sites of ribosome

Answer 9

2 - 1st tRNA binds to P site and begins adding further tRNA at site A

• this repeats until protein is finished

Question 10

Which of the following described termination?

1 - codon signalling termination is recognised by P site
2 - 1st tRNA binds to P site and begins adding further tRNA at site A
3 - 50S and 30S subunits bind to mRNA forming ribosome-mRNA complex
4 - tRNA bind to the A, P and E binding sites of ribosome

Answer 10

1 - codon signalling termination is recognised by P site

Question 11

What is the mechanism of action of Chloramphenicol?

1 - binds to penicillin binding protein
2 - interfere with NAG and NAMs
3 - bind to 50S ribosome
4 - irreversibly binds the 50S ribosome subunit and inhibits protein synthesis

Answer 11

4 - irreversibly binds the 50S ribosome subunit and inhibits protein synthesis

Question 12

Is Chloramphenicol bactericidal or bacteriostatic?

Answer 12

• bacteriostatic
• BUT can be bactericidal at high doses

Question 13

Chloramphenicol is bacteriostatic in its action, but kills which of the following?

1 - E.coli
2 - H. influenzae
3 - Klebsiella
4 - Staphylococcus aureus

Answer 13

2 - H. influenzae

Question 14

Is Chloramphenicol a broad or narrow spectrum antibiotic?

Answer 14

• broad spectrum
• acts of Gram +, Gram - and aerobic and anaerobic organisms

Question 15

Which of the following is Chloramphenicol indicated for use in?

1 - bacterial conjunctivitis
2 - otitis externa
3 - COPD exacerbation
4 - pneumonia

Answer 15

1 - bacterial conjunctivitis

2 - otitis externa
- generally last choice if other medications have failed

Question 16

All of the following are adverse events caused by Chloramphenicol. Which of these is the most common?

1 - bone marrow suppression
2 - aplastic anaemia
3 - transient stinging/burning/itching
4 - grey baby syndrome
5 - optic and peripheral neuritis

Answer 16

3 - transient stinging/burning/itching

• bone marrow suppression = occurs using high doses, but rare
• grey baby syndrome = circulatory collapse in neonates unable to excrete and metabolise the drug

Question 17

Chloramphenicol is contraindicated in all of the following EXCEPT which one?

1 - history of hypersensitivity reactions
2 - hepatic impairment
3 - bone marrow disorder
4 - 3rd trimester of pregnancy
5 - breastfeeding mums
6 - children <2 y/o

Answer 17

2 - hepatic impairment
- not contraindicated
- BUT dosage and monitoring needs to be altered

Question 18

Which enzymes does Chloramphenicol inhibit and thus prevents the metabolism of other drugs?

1 - cytochrome P450 (variations CYP3A4 and CYP2C19)
2 - pancreatic lipase
3 - glutathione
4 - HMG-CoA reductase

Answer 18

1 - cytochrome P450 (variations CYP3A4 and CYP2C19)

Question 19

How is Chloramphenicol administered for superficial eye infections?

1 - orally
2 - IV
3 - topical administration
4 - sublingual

Answer 19

3 - topical administration
- typically every 2h as drug is removed by tears and blinking

• medication is presented as a %
• e.g. 0.5g in 100ml = 0.5% solution

Question 20

Chloramphenicol is indicated in bacterial conjunctivitis and otitis externa. Can the drug be used interchangeably?

Answer 20

• no
• ear and eye drops made differently and could cause adverse events

Question 21

When prescribing any antibiotics, in accordance with antibiotic stewardship, which of the following must be document on the prescription and in the patients notes?

1 - indication
2 - review date
3 - treatment duration
4 - all of the above

Answer 21

4 - all of the above

Question 22

If prescribed as IV, how long should it be before the antibiotics are switched to oral where appropriate?

1 - 12h
2 - 24h
3 - 48h
4 - 72h

Answer 22

3 - 48h

Question 23

Broad spectrum antibiotics are prescribed empirically, when we do not know the specific cause of the infection. However, what is the main driver to switch antibiotics to a narrow spectrum antibiotic?

1 - cost
2 - patients request
3 - microbiology results
4 - allergies

Answer 23

3 - microbiology results