Antibiotics Flashcards
Benzyl-penicllin - route and target
IV admin normally. First choice antibiotic for streptococcal infection. Narrow spectrum
Amoxicillin - route and what is used to treat
oral - much higher bioavailability than previous penicillins. Gram negatives, streptococcus, enterococcus, clostridium
Majority of E.coli are resistant
Flucloxacillin - route and main target
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
usefulness of beta-lactamase inhibitors
Greatly broadens spectrum of penicillins against Gram –ves and S. aureus
carbapenems
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
Name the monobactam antibiotic
Aztreonam. Given IV, does not have cross-reactivity with the penicillins. For use with gram negatives
name two macrolides
erythromicin and clarithromycin
which ribosomal subunit do they macrolides act against?
50S
what does the spectrum of an antibiotic refer to?
Give an example of a broad and narrow spectrum
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
Clostridium and bacteriodes are what class of bacteria
anaerobes
Enterococcus and staphyloccous are members of what class of bacteria
Gram +
name 4 gram - bacteria
Pseudomonas, haemophilus, neisseria, E.coli
Cephalosporins - what are they useful against?
mainly gram negatives e.g. E.coli, neisseria, haemophilus. Gram positive - strep.
What bacteria is vancomycin active against?
Gram + in particular MRSA.
What is oral vancomycin used to treat
C.diff
why is vancomycin given as a loading dose
has a long half-life
name a reason vancomycin is generally effective against resistant organisms
It is not dependent on penicillin binding proteins
Describe some common toxicities seen with vancomycin
nephrotoxicity - with higher doses.
Red man syndrome is infused too quickly.
Ototoxicity
name two common bacterial causes of cellulitis and an antibiotic that would cover these
staphs and streps
Would likely be covered by flucloxacillin
What are macrolides good for treating?
Show a good spectrum of activity against gram + and respiratory gram -. Are also used against the atypicals e.g. legionella, mycoplasma and chlamydia.
Adverse effects of macrolides
D and V, QT prolongation, hearing loss (with long term use)
Which antibiotic is particularly known for causing C diff?
Clindamycin - very good activity against anaerobes so very good at disrupting the colonic flora.
Name the four C differgic antibiotics
Clindamycin, co-amoxclav, cephalosporins, ciprofloxacin
How is chloramphenicol commonly used?
Topical therapy to the eyes.
What class of antibiotics does gentamicin belong to ?
aminoglycosides.
name the mechanism of action of gentamicin
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.
describe the toxicity of gentamicin
nephrotoxicity: main concern.
Ototoxicity - common.
neuromuscular blockade: common in myasthnia gravis patients only.
What gent can be used against
gram negatives. Staph, Strep.
Name a tetracycline and what sort of infections they are used in
Doxycycline
used in respiratory infections e.g. staphs and streps. Are active against atypicals as well
Are also active against haemophilus and neisseria.
Issues with tetracyclines
to be avoided in children and pregnant women - bone abnormalities, tooth discolouration
How do Quinolones work and give an example
What do they work against
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
In what condition would you use rifampicin and with which drugs?
TB.
Standard short course used. Four drugs
What is the mechanism of action of trimethoprim and what is it used for
Inhibits folate synthesis
First-line therapy for uncomplciated UTI
MOA of metronidazole and what its acts against
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
antibiotic considered safe during pregnancy
beta lactams, macrolides, anti-tuberculants
