Antibiotics

Question 1

Benzyl-penicllin - route and target

Answer 1

IV admin normally. First choice antibiotic for streptococcal infection. Narrow spectrum

Question 2

Amoxicillin - route and what is used to treat

Answer 2

oral - much higher bioavailability than previous penicillins. Gram negatives, streptococcus, enterococcus, clostridium
Majority of E.coli are resistant

Question 3

Flucloxacillin - route and main target

Answer 3

Synthetic penicillin developed to be resistant to beta-lactamase produced by staphylococci
• Antibiotic highly active against:
– Staphylococcus aureus (not MRSA)
– Streptococci
• No activity at all against gram negative organisms
• Can be given orally but nausea limits dose

Question 4

usefulness of beta-lactamase inhibitors

Answer 4

Greatly broadens spectrum of penicillins against Gram –ves and S. aureus

Question 5

carbapenems

Answer 5

Ultra-broad spectrum beta-lactam antibiotics.
• Excellent spectrum of activity against Gram +ves and Gram –ves
• No activity against MRSA
• Resistant to beta-lactamases but new beta-lactamases are emerging that can degrade
e.g. meropenem

Question 6

Name the monobactam antibiotic

Answer 6

Aztreonam. Given IV, does not have cross-reactivity with the penicillins. For use with gram negatives

Question 7

name two macrolides

Answer 7

erythromicin and clarithromycin

Question 8

which ribosomal subunit do they macrolides act against?

Answer 8

50S

Question 9

what does the spectrum of an antibiotic refer to?

Give an example of a broad and narrow spectrum

Answer 9

The range of bacterial species effectively treated by the antibiotic
broad: meropenem treats almost all gram + and gram -. Resistance is rare except for MRSA.
Narrow: benzylpenicillin - highly active against streptococci but not much else

Question 10

Clostridium and bacteriodes are what class of bacteria

Answer 10

anaerobes

Question 11

Enterococcus and staphyloccous are members of what class of bacteria

Answer 11

Gram +

Question 12

name 4 gram - bacteria

Answer 12

Pseudomonas, haemophilus, neisseria, E.coli

Question 13

Cephalosporins - what are they useful against?

Answer 13

mainly gram negatives e.g. E.coli, neisseria, haemophilus. Gram positive - strep.

Question 14

What bacteria is vancomycin active against?

Answer 14

Gram + in particular MRSA.

Question 15

What is oral vancomycin used to treat

Answer 15

C.diff

Question 16

why is vancomycin given as a loading dose

Answer 16

has a long half-life

Question 17

name a reason vancomycin is generally effective against resistant organisms

Answer 17

It is not dependent on penicillin binding proteins

Question 18

Describe some common toxicities seen with vancomycin

Answer 18

nephrotoxicity - with higher doses.
Red man syndrome is infused too quickly.
Ototoxicity

Question 19

name two common bacterial causes of cellulitis and an antibiotic that would cover these

Answer 19

staphs and streps

Would likely be covered by flucloxacillin

Question 20

What are macrolides good for treating?

Answer 20

Show a good spectrum of activity against gram + and respiratory gram -. Are also used against the atypicals e.g. legionella, mycoplasma and chlamydia.

Question 21

Adverse effects of macrolides

Answer 21

D and V, QT prolongation, hearing loss (with long term use)

Question 22

Which antibiotic is particularly known for causing C diff?

Answer 22

Clindamycin - very good activity against anaerobes so very good at disrupting the colonic flora.

Question 23

Name the four C differgic antibiotics

Answer 23

Clindamycin, co-amoxclav, cephalosporins, ciprofloxacin

Question 24

How is chloramphenicol commonly used?

Answer 24

Topical therapy to the eyes.

Question 25

What class of antibiotics does gentamicin belong to ?

Answer 25

aminoglycosides.

Question 26

name the mechanism of action of gentamicin

Answer 26

Reversibly binds to the 30s bacterial ribosome: bacteriostatic action. has a prolonged post-antibiotic effect.
Also has a poorly understood effect on cell membrane - bactericidal.

Question 27

describe the toxicity of gentamicin

Answer 27

nephrotoxicity: main concern.
Ototoxicity - common.
neuromuscular blockade: common in myasthnia gravis patients only.

Question 28

What gent can be used against

Answer 28

gram negatives. Staph, Strep.

Question 29

Name a tetracycline and what sort of infections they are used in

Answer 29

Doxycycline
used in respiratory infections e.g. staphs and streps. Are active against atypicals as well
Are also active against haemophilus and neisseria.

Question 30

Issues with tetracyclines

Answer 30

to be avoided in children and pregnant women - bone abnormalities, tooth discolouration

Question 31

How do Quinolones work and give an example

What do they work against

Answer 31

target DNA replication.
E.g. Ciprofloxacin, levofloxacin.
Ciprofloxacin - active against the gram negatives and is commonly used in UTI/abdominal infection
Levofloxacin - has less gram negative activity but stronger gram positive action

Question 32

In what condition would you use rifampicin and with which drugs?

Answer 32

TB.

Standard short course used. Four drugs

Question 33

What is the mechanism of action of trimethoprim and what is it used for

Answer 33

Inhibits folate synthesis

First-line therapy for uncomplciated UTI

Question 34

MOA of metronidazole and what its acts against

Answer 34

enters cell by passive diffusion and produces free radicals which the anaerobic bacteria are incapable of clearing - oxidative damage leading to inhibition of nucleic acid synthesis through disruption of the DNA
Active against anaerobic bacteria

Question 35

antibiotic considered safe during pregnancy

Answer 35

beta lactams, macrolides, anti-tuberculants