Mechanism of action of chloramphenicol is -
Ans. is 'b' i.e., SOS ribosome inhibitor * The mechanism of action of antimicrobials can be divided into :1. Inhibition of cell wall synthesis# Drugs inhibiting cell wall synthesis are : b-lactam antibiotics (penicillin, cephalosporins, monobactoms, carbapenems), cyclosporine, bacitracin, vancomycin, fosfomycin.# All antibiotic inhibiting cell wall synthesis are bactericidal.2. Inhibition of cell membrane function# Drugs acting on cell membrane are polypeptides (polymyxin, colistin, tyrothricin), polyenes (amphotericin B, nystatin, hamycin), azoles (ketoconazole, fluconazole, itraconazole).# All antimicrobials that act on cell membrane are bactericidal.3. Inhibition of protein synthesis (translation)# Drugs acting by inhibiting protein synthesis are tetracyclines, chloramphenicol, aminoglycosides, erythromycin, clindamycin, linazolide.# All protein synthesis inhibitors are bacteriostatic except aminoglycosides and streptogramins which are bactericidal.# These drugs can be divided into :a) Based on the steps of translation (protein synthesis) on which drug act:i) Freeze initiation : Aminoglycosides.ii) Inhibit elongation : Tetracyclines, puromycin, chloramphenicol.iii) Inhibit translocation : Clindamycin, erythromycin.iv) Causing premature termination : Puromycin.b) Based on ribosome on which they act:i) 30 S ribosome: Tetracycline, streptomycin.ii) 50 S ribosome : Chloramphenicol, erythromycin, clindamycin, Linezolid, pleuromutilins (retapamulin).iii) Both 30S and 50S ribosomes : Aminoglycosides (except streptomycin).4. Interference with nucleic acid synthesis# These drugs may be :1. Drugs directly affecting nucleic acids (RNA or DNA)* DNA gyrase inhibitors - Quinolones (nalidixic acid and fluoroquinolones) and novobiocin.* Drugs destroying DNA - Metronidazole, nitrofurantoin.* Nucleotide/nucleoside analogues - get incorporated into DNA or RNA and lead to formation of faulty nucleic acid that may be unstable or nonfunctional. Drugs are - Acyclovir, Zidovudin, Idoxuridine.* DNA dependent RNA polymerase inhibitors - Rifampicin2. Drugs acting indrectly by affecting intermediary metabolism* They either inhibits folate synthase (sulfonamide, PAS, dapsone) or dihydrofolate reductase (Trimethoprim, pyrimethamine) so that tetrahydrofolate can not be synthesized, which is essential for the synthesis of DNA.
Cell wall synthesis inhibitor
50 S ribosome inhibitor
30S ribosome inhibitor
glycopeptidase inhibitor
Anti Microbial