Antibiotics Classification

Antibiotics Classification

Antibiotics Classification is done by Mode of Mechanism.

1- Cell Wall Synthesis Inhibitors.

v Penicillins
v Cephalosporin
v Vancomycin
v Carbapenems
v Beta-Lactum Inhibitor
v Aztreonam
v Polymycin
v Bacitracin

2- Protein Synthesis Inhibitors.

Inhibit 30s Ribosome Subunit

  v Aminoglycosides
  v Tetracycline

   II.         Inhibit 50s Ribosome Subunit 

  v Macrolids
  v Chloramphenicol
  v Clindamycin
  v Linezolids
  v Streptogramins

3- DNA Synthesis Inhibitors.

  v Floroquinolones
  v Metronidazole
  v Quinolones

4- RNA Synthesis Inhibotors.

  v Rifampin

5- Mycolic Acid Synthesis Inhibitors.

  v Isoniazid

6- Folic acid Synthesis Inhibitors.

  v Sulfonamides

  v Trimethoprime.

Antibiotics Classification on the basis of Bacteriostatic and Bactericidal activity.

   A.  Bacteriostatic

  v Sulfonamides
  v Chloramphenicol
  v Aminoglycosides
  v Oxytetracycline

   B.   Bactericidal

  v Penicillin
  v Cephalosporin
  v Quinolones
  v Microlids

Mechanism of Action of Antibiotics.

1- Inhibition of cell wall synthesis

Gram Positive (+) bacterial cell wall is made up of chemically distinct complex cross linked polymer peptidoglycan. Penicillin and Cephalosporin inhibit the transpeptidaze enzyme which is responsible for transpeptidation reaction. So there is no formation of peptidoglycan and cell wall. Penicillin and Cephalosporin are similar to Accyl-D-alanin in nature. They are bactericidal in action. Vencomycin disrupts peptidoglycan cross linkage. Polymyxin and Bacitracin are topical used and these both alter the cell membrane by cationic detergent like activity and disrupt cytoplasmic membrane respectively.

2- Inhibition of Protein Synthesis.

      I.            Inhibit 30s Ribosome Subunit

      a)     Aminoglycosides

      Irreversibly bind to specific protein in 30s subunit of bacterial ribosome. Blocking bacterial protein synthesis by interfering with initial complex and also they cause misreading of mRNA e.g. Gentamycin

      b)    Tetracycline

           They bind to acceptor part of 30s subunit of bacterial ribosome and prevent the binding of Aminoacyl- tRNA and block protein Synthesis.

   II.            Inhibit 50s Ribosome Subunit

     a.     Chloramphenicol

It bind to 50s subunit of ribosome and block peptidal transferase activity and transpeptidation don’t takes place.

     b.     Macrolids

It bind to 50s subunit of bacterial ribosome. It interferes with Aminoacyl-translocation reaction. It reversibly bind to 50s subunit.

     c.      Clindamycin

It bind to 50s ribosome subunit and block peptide elongation. It inhibits peptidyl- transferase by interfering with binding of amino acid-acyl-tRNA complex.

3-  DNA Synthesis Inhibitors.

                       i.     Quinolones

They inhibit DNA gyrase or topoisomerases required for super coiling of DNA bind to Alpha-subunit.

    i       ii.  Metronidazol

Metabolic cytotoxic byproduct disrupts DNA.

4- RNA Synthesis Inhibitors.

  v Rifaampin

It binds to DNA dependent RNA- polymerase stop RNA transcription by inhibiting RNA polymerase.

5- Mycolic Acid Synthesis Inhibitor.

Only selective against intracellular and extracellular mycobacterium tuberculosis. Stop mycolic acid synthesis which interferes with cell wall synthesis. They are bactericidal.

6- Nucleic Acid/Folic Acid Inhibitors.

They have antimetabolic Activity. They block synthesis of tetrahydro-folic acid which is requiring for synthesis of nucleic acid precursors Adenine, Guanine and Thiamine. P-amino benzoid acid (PABA) is essential for folic acid synthesis. Sulfonamides are structural analogue of PABA. They bind in place of PABA in folic acid synthesis cycle. Thus disturb folic acid synthesis. Trimethoprim inhibit the enzyme dihydrofolate reductase enzyme and inhibit synthesis of tetrahydofolic acid.

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