Friday, 18 October 2013

Classification of antimicrobial agents: On the basis of their mechanism of action

Antimicrobial agents are used for the treatment of the microbial infections in the body and the treatment is termed as chemotherapy. Paul Ehlrich is known as the father of Chemotherapy who used Arsphenamine for the treatment of Syphilis. Chemotherapy is an important perspective for the student’s GPAT preparation as lots of questions are asked from this section. Here, we are introducing the classification of antimicrobial agents on the basis of their mechanism of action.
Classifiaction of antimicrobial agents

1.       Antibiotics that inhibits Bacterial Cell Wall synthesis
a)      Pencillins, Cephalosporins, Carbepenam and Monobactam: These drugs inhibit the transpeptidase enzyme used in the bacterial cell wall synthesis.
b)      Vancomycin: This drug makes complex with C-terminal D-alanine residues of petisoglycan precursors.
c)       Cycloserine: It inhibits alanine racemase and D-alanyl-D-alanine synthetase.

2.       Antibiotics that inhibit Ribosome function and prevent protein synthesis
a)      Aminoglycosides: It causes misreading in mRNA
b)      Tetrayclines: This class of drug binds with 30S ribosomes and inhibits the binding of aminoacyl-tRNA into the A site of the bacterial ribosome.
c)       Chloramphenicol: It binds with the peptidyltransferase enzyme on the 50S ribosome and inhibits protein synthesis.
d)      Spectinomycin
e)      Azithromycin and Clarithromycin: Inhibits translocation which leads the protein synthesis inhibition.

3.       Antibiotics that affect the function of cytoplasmic membranes
a)      Antifungal drugs: Amhotericin B, Ketoconazole, Clotrimazole, Fluconazole, Miconazole and Nystatin.
b)      Bacitracin & Polymyxin B & E: They cause the leaking of nuclear material which leads to the cell death.
c)       Gramicidin: It produces aqueous pores in the cell membrane.

4.       Antibiotics that inhibit Nucleic acid synthesis
a)      Agents that interfere with Nucleotide synthesis:
·         Zidovudine: DNA polymerase inhibition.
·         Acylovir: Thymidine kinase and DNA polymerase inhibition of Herpes virus.
·         Flucocytosine: Thymidylate synthetase inhibition.
b)      Agents that interfere with DNA replication:
·         Metrindazole: DNA strand breakage by the reduced Nitro group.
·         Quinolones: DNA gyrase inhibition
c)       Agents that inhibit RNA polymerase:
·         Rifamycins
d)      Agents that interfere with the precursor synthesis:
·         Sulfonamides: Inhibit the conversion of Pteridine & p-Amino Benzoic acid (PABA) into dihydrofolic acid.
·         Trimethoprim: Inhibits the conversion dihydrofolic acid into tetrahydrofolic acid.
e)      Agents that interfere with the Template function of DNA:

·         Chloroquine & Proflavine

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