Antibiotics - Cephalosporins

Question 1

Bacterial cell walls are composed of peptidoglycans, which are long amino polysaccharides. What 2 amino polysaccharides make up the peptidoglycan wall?

1 - N-acetylglucosamine (NAG)
2 - N-acetylmuramic acid (NAM)
3 - pili
4 - fimbraie

Answer 1

1 - N-acetylglucosamine (NAG)
2 - N-acetylmuramic acid (NAM)

• organised in an alternating pattern

Question 2

The 2 amino polysaccharides, N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) that make up the peptidoglycan wall are connected at their tips by tetrapeptide and pentapeptide chains, protruding from NAM subunits.
These peptide chains can link to other peptide chains from the neighboring strands through a process known as transpeptidation. What enzyme is crucial for transpeptidation and the formation of a strong cell wall?

1 - B-lactamase
2 - penicillin binding protein
3 - deoxycholic proteins
4 - bacterial peptidase

Answer 2

2 - penicillin binding protein

• essentially locks together tetrapeptide and pentapeptide chains together

Question 3

The principle of penicillin B-lactam antibiotics is that they resemble tetrapeptide chains that hold the cell wall together. Which of the following then happens if the penicillin binding protein (PBB) binds with the B-lactam molecule of the antibiotic?

1 - binds to PBB permanently
2 - PBB unable to perform transpeptidation
3 - cell wall becomes weak and unstable
4 - cell wall will fail when bacteria try to multiply
5 - all of the above

Answer 3

5 - all of the above

Question 4

How are we able to distinguish between gram positive and gram negative bacteria?

1 - shape of bacteria
2 - if they contain a cell membrane
3 - if they contain RNA or DNA
4 - if dye binds to bacterial wall

Answer 4

4 - if dye binds to bacterial wall
- gram negative cannot retain the dye as the walls are too thin

Question 5

Cephalosporins, like penicillins are a B-lactam antibiotic. All of the following are the key Cephalosporins that we need to know about EXCEPT which one?

1 - Cephalexin
2 - Ceftriaxone
3 - Clarithromycin
4 - Ceftazidime

Answer 5

3 - Clarithromycin

• Cephalosporins are more resistant to B-lactamase due to structural differences with penicillin

Question 6

Cephalosporins (Cephalexin, Ceftriaxone and Ceftazidime), like penicillins are a B-lactam antibiotics. What is the mechanism of action of these antibiotics?

1 - inhibit NAG-NAM subunit formation
2 - binds and inactivates penicillin binding proteins
3 - inhibit protein synthesis
4 - inhibits DNA gyrase

Answer 6

2 - binds and inactivates penicillin binding proteins

• bacterial cell wall becomes unstable and cell lyses

Question 7

Cephalosporins (Cephalexin, Ceftriaxone and Ceftazidime) are B-lactam antibiotics given orally are generally a 2nd or 3rd choice treatment for the treatment of which of the following?

1 - UTIs
2 - pneumonia (hospital acquired and other lower respiratory infections)
3 - epiglottis
4 - acute pyelonephritis
5 - all of the above

Answer 7

5 - all of the above

• parentally forms are reserved for very severe or complicated infections

Question 8

Cephalosporins (Cephalexin, Ceftriaxone and Ceftazidime) are B-lactam antibiotics that have shown good activity against which Gram negative bacteria?

1 - Streptococcus pneumoniae
2 - Enterococci
3 - Pseudomonas aeruginosa
4 - Staphylococcus aureus

Answer 8

3 - Pseudomonas aeruginosa
- all others are gram +

• has some effectiveness against Staphylococcus aureus

Question 9

Cephalosporins (Cephalexin, Ceftriaxone and Ceftazidime) are B-lactam antibiotics. Are these broad or narrow spectrum?

Answer 9

• broad spectrum
• good against Gram + cocci (staphylococcus, streptococcus, anaerobic streptoocci)
• good against Gram - rods (E.coli, proteus mirabilis, Klebsiella)

Question 10

Are Cephalosporins bactericidal or bacteriostatic?

Answer 10

• bactericidal
• induce bacterial swelling, lysis and death

Question 11

All of the following are adverse events caused by Cephalosporins, but which is the most common?

1 - GI upset
2 - antibiotic associated colitis
3 - hypersensitivity reactions
4 - seizures
5 - leucopenia

Answer 11

1 - GI upset

• abdominal pain and diarrhoea

Question 12

GI upset is the most common adverse event of Cephalosporins. although less common than penicillins. Why does this occur?

1 - irritates mucosal membrane
2 - has osmotic effect inducing diarrhoea
3 - healthy flora are killed causing C. difficile and colitis
4 - stimulates serotonin receptors and induces nausea and vomiting

Answer 12

3 - healthy flora are killed causing C. difficile and colitis

Question 13

Cephalosporins should be used with caution in all of the following EXCEPT which one?

1 - older adults at risk of C. difficile
2 - hospitalised patients at risk of C. difficile
3 - history of immediate type hypersensitivity
4 - severe renal impairment
5 - all patients with community acquired pneumonia

Answer 13

5 - all patients with community acquired pneumonia

• caution in older adults, but not ALL patients

Question 14

If allergic to one type of b-lactam antibiotic, does that mean you are allergic to all b-lactam antibiotics?

Answer 14

• yes
• including cephalosporins

Question 14

Cephalosporins have several drug interactions that can lead to nephrotoxicity. Which of the following medications can contribute to nephrotoxicity when combined with Cephalosporins?

1 - gentamicin
2 - Ibuprofen
3 - celecoxib (pain medication)
4 - all of the above

Answer 14

4 - all of the above

Question 15

GI upset is the most common adverse event of Cephalosporins as healthy flora are killed causing C. difficile and colitis. This can increase the anticoagulant effect and bleeding risk of which drug?

1 - heparin
2 - enoxaparin
3 - edoxaban
4 - warfarin

Answer 15

4 - warfarin

• healthy gut flora are important for vitamin K absorption

Question 16

In severe infections how are broad spectrum antibiotics typically administered?

1 - oral
2 - IV
3 - IM
4 - suppository

Answer 16

2 - IV

• standard Cephalosporins dose = 4g/daily

Question 17

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 17

4 - all of the above

Question 18

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 18

3 - 48h

Question 19

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 19

3 - microbiology results