Antimicrobials Flashcards
Name some groups of antibiotics which inhibit cell wall synthesis.
B-lactams - within this are penicillins, cephalosporins
Against which type of bacteria are B-lactams most effective?
Gram +ve bacteria due to their thick cell wall.
How do B-lactams work?
They bind to transpeptidases which normally form peptide cross-links in the peptidoglycan cell wall structure.
This leads to a weakning in the cell wall, and the contents bulge out into a spheroplast which are unstable and lead to cell lysis.
Give the mechanism of action of chloramphenicol.
What is it used for?
Binds to 50S subunit of bacterial ribosome.
Prevents formation of peptide bonds.
Used for eye infections including conjunctivitis.
What is the mechanism of action of erythromycin?
Binds to 50S subunit, prevents movement of mRNA along ribosome.
Mechanism of action of clindamycin.
Binds to 50S subunit. Prevents protein elongation.
Give 2 examples of macrolides.
Clarithromycin, erythromycin
Mechanism of action of tetracyclines
Prevents attachment of tRNA to the mRNA-ribosome complex.
Mechanism of action of streptomycin
What is it used for?
Binds to 30S subunit of bacterial ribosome. Prevents code from being read correctly.
Used for TB.
In which group should tetracycline antibiotics be avoided and why?
Children as tetracyclines can cause teeth discolouration.
Mechanism of ciprofloxacin.
What is it used for?
Inhibits bacterial DNA gyrase which usually uncoils nucleic acid so it can be read.
It is a good broad-spectrum antibiotic against gram +Ve and -ve bacteria.
Mechanism of metronidazole.
What is it used for?
Inhibits DNA synthesis.
It is used for anaerobic microbes e.g.
bacteria - bacterial vaginosis
Protozoa - trichonosomiasis, giardia, guinea worm
Which class of antibiotics cannot be given orally?
Give an example of an antibiotic in this class.
Aminoglycosides cannot be given orally as they are poorly absorbed from the GI tract.
An example is gentamicin, streptomycin.
Which organism is piperacillin most active against?
Pseudomonas aeruginosa.
Piperacillin is a b-lactam antibiotic but it has added activity against gram -ves.
What drug causes cinchonism? Give some symptoms.
Quinine.
Mild cinchonism = flushing, sweating, tinnitus, blurred vision, confusion, reversible high-frequency hearing loss, vertigo, N+V
Severe cinchonism - deafness, somnolence, blindness, anaphylaxis, arrhythmias, blackwater fever
