Pharmacology of antibiotics Flashcards
What are the targets for antibiotics
Bacterial cell wall
Bacterial ribosomes
Bacterial folate metabolism
Bacterial DNA gyrases
What does Amoxicillin contain
Beta-lactam ring
What do penicillins target and how
Bacterial cell wall synthesis
-By binding irreversibly to a transpeptidase which cross-links peptidoglycans in the bacterial cell wall
What are penicillins only effective against
Dividing organisms (because division requires cell wall synthesis)
What are penicillins
Bacteriacidal (cause lysis of bacteria)
What are some penicillins inactivated by and what are these secreted from
Beta-lactamases secreted by resistant bacteria
What inhibits beta lactamases
Clavulanic acid
Where is clavulanic acid included and why
With some agents like amoxicillin to inhibit the beta lactamases
Another example of beta lactam antibiotics
Cephalosporins
how do cephalosporins work
Inhibit transpeptidases which cross link the peptidoglycan chains
Whom should you be cautious about giving cephalosporins to
Those with a penicillin allergy because they show cross-reactivity with penicillins
How do glycopeptides work
Inhibit bacterial cell wall synthesis by inhibiting the growth of the peptidoglycan chain
What are glycopeptides usually used to manage
Severe infections due to superbugs (e.g. MRSA)
How do tetracyclines work
inhibit protein synthesis by binding to the 30s subunit of the bacterial ribosome and preventing tRNA from binding at the acceptor site
Are tetracyclines bacteriostatic or bactericidal
Bacteriostatic
What do macrolides do
Prevent the translocation of the 50s subunit of the bacterial ribosome along the mRNA (so stop protein synthesis)
Are macrocodes bacteriostatic or bactericidal
Bacteriostatic
What is used as an alternative to penicillin in those with a penicillin allergy
Macrolides
Which drug is associated with a range of drug interactions and why
Macrolides
-They are cytochrome P450 inhibitors and so are increase concentrations of interacting drugs
How do aminoglycosides act
Bind irreversibly to the 30s subunit of bacterial ribosomes which leads to the misreading of mRNA and therefore interferes with protein synthesis
What are aminoglycosides used to manage
Gram negative bacteria
What drug can be mixed with penicillin to form a synergy and what effect does this have
Aminoglycosides
-Breakdown of cell wall and so increases uptake of aminoglycosides
What do quinolones do
Inhibit bacterial DNA gyrase (topoisomerase 2) and topoisomerase IV
What do quinolones do to gram negative bacteria
Inhibit DNA gyrase and they inhibit the supercoiling of bacterial DNA which is essential for DNA repair and replication
What is trimethoprim structurally related to
Folate
What does trimethoprim do
Folate antagonist and inhibit the bacterial dihydrofolate reductase which converts folate to tetrahydrofolate
Drugs which inhibit folate
Sulphonamides and trimethoprim
What do sulfonamides do and what does this mean
Inhibit growth of bacteria by competitively inhibiting enzyme dihydropteroate synthase which is involved in the synthesis of folate
-The availability of DNA and RNA precursors are reduced
What drug is used against anaerobic bacteria
Metronidazole
