Antibiotics

Question 1

What are the 4 MOAs of abx?

Answer 1

1. disruption of the cell wall
2. inhibition of nucleic acid synthesis
3. Anhibition of protein synthesis
4. anti-metabolite function

Question 2

What is the MOA of beta lactams?

Give 2 egs (3 listed)

Answer 2

Disrupt the formation of the bacterial cell wall by inhibiting the cross links in the peptidoglycan lattice. Covalent bonds are formed with the penicillin binding proteins.

• penicillin
• cephalosporins
• carbapenems

Question 3

What is the MOA of glycopeptides?

Give 1 eg (2 listed)

Answer 3

Blocks the glycopeptide polymerisation of the bacterial cell wall

• vancomycin
• teicoplanins

Question 4

What is the MOA of quinolones?

(Give 2 egs)

Answer 4

Inhibit the enzymes involved with DNA coiling

Question 5

What is the MOA of metronidazole?

Answer 5

Damages bacterial DNA and inhibits DNA synthesis

Question 6

Which abx inihibit RNA polymerase to prevent transcription of mRNA?

Answer 6

Rifampicin

Question 7

Where do tetracycline and gentamycin act?

Answer 7

30s subunit of bacterial ribosomes - misreading of codons so no protein sythesis

Question 8

Which antibiotics inhibit bacterial folate production?

(2 listed)

Answer 8

• Sulphonamides
• Trimethoprim

Question 9

Which bacteria are the most likely cause of skin infections? (which abx for tx?)

Answer 9

• Streptococcus –> penicillin V
• Staphylococcus –> flucloxacillin

Question 10

Which abx is the best choice for tx of an abscess?

Answer 10

Metronidazole - effective against anaerobes + good oral absorption

Question 11

What is the dose of metronidazole?

What caution should be explained to pts?

Answer 11

400mg TDS

Don’t drink alcohol

Question 12

What is the IV form of penicillin?

Answer 12

Benzylpenicillin

Question 13

Which part of penicillin can pts become allergic to?

Which other abx can 10% of pts also be allergic to with this?

Answer 13

Beta lacatam ring

Cephalosporin - has a similar structure

Question 14

What does clavulanic acid do?

Answer 14

β lactamase inhibitor - this mornally breaks down the lactam ring in penicillin so giving clavuramic acid helps broaden the spectrum.

e.g. co-amoxiclav (same as augmentin)

Question 15

What is 90% of Staphylococcus resitiant to?

Which antibiotic was developed instead?

Answer 15

penicillin - they produce beta lactamase enzymes

Flucloxacillin

Question 16

Which 3 abx should be prescribed to treat an infected finger?

Answer 16

• Penicillin - to cover Strep
• Flucloxacillin to cover Staph
• Metronidazole to cover anaerobes

Question 17

What should be monitored in malnourished patients on antibiotics?

Answer 17

Albumin - reduced albumin in malnutrition so increases free drug

Question 18

What should be considered when prescribing abx to someone with a high protein mass?

Answer 18

Dose - high protein mass means less free drug e.g. flucloxacillin is 95% bound to protein and only 5% is free to act.

Question 19

Name 3 macrolides

Answer 19

• Erythromycin
• Clarythromycin
• Azithromycin

Question 20

When are macrolides prescribed?

Answer 20

When treating:

• Gram +ve –> Staph and Strep
• Gram -ve –> H influenzae, N. meningitidis, Legionella pneumophilia
• Mycoplasma

Question 21

What reduces the absorption of erythromycin and azithromycin? - what instructions should be given to pts?

Answer 21

Food- must take 20mins before food

Question 22

What adverse effect can happen following IV administration of macrolides?

Answer 22

Phlebitis