Antibacterials: inhibitors of bacterial protein synthesis

sophietevans
Flashcards by sophietevans, updated more than 1 year ago
sophietevans
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From the 26-02-14 Drugs and Disease lecture.

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Question Answer
Is chloramphenicol's mechanism of action bacteriostatic or bacteriocidal? Chloramphenicol is generally bacteriostatic (e.g. for Salmonella spp.), but is bacteriocidal for Haemophilus influenza.
How does chloramphenicol inhibit bacterial protein synthesis? It binds irreversibly to peptidyl transferase in the 50S subunit of the bacterial ribosome, inhibiting it from catalysing the formation of a peptide/amide bond between the amino acids on the transfer RNA in the acceptor site. This prevents the ribosome from translocating to the next codon on the bacterial mRNA, preventing elongation of bacterial proteins.
What are the serious adverse effects of chloramphenicol administration? It can cause bone marrow depression, resulting in aplastic anaemia and leukopenia - this can prolong treatment time (as antibacterials are supposed to aid and create time for host immune action) and risks opportunistic infection.
Which drug family does tetracycline belong to? The tetracyclines.
Is tetracycline bacteriostatic or bacteriocidal? It's mechanism of action is bacteriostatic, like that of chloramphenicol.
List some infections that tetracycline is useful in treating. Lyme disease (Borellia borgderfia), Bacillus anthracis, rickettsial and chlamydial infections. It is also broad spectrum.
Like chloramphenicol, tetracycline inhibits protein synthesis at the elongation stage. How does its mechanism of action differ? Which chloramphenicol inhibits the peptidyltransferase enzyme in the 50S ribosomal subunit irreversibly, preventing peptide chain elongation, tetracycline binds to the 30S ribosomal subunit and prevents aminoacyl-tRNA from binding. Depletion of all bacterial proteins results, preventing further bacterial growth.
Tetracyclines also inhibit protein synthesis in mammalian cells, particularly in the mitochondria - so what stops them from causing havoc in the host body during treatment? Selectively for bacterial cells results from bacteria being able to generate the pH gradient across the cell membrane that is necessary for tetracyclines to move through membrane porins more quickly than mammalian cells.
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