Classification of Antimicrobials



Classification of Antimicrobials
I. Basing on nature of antimicrobial action:
A. Antibacterial (bacteriostatic and bactericidal), antiviral, antifungal, antiprotozoal, anthelmintic, antirickettsial, antimalarial, antitubercular, acaricide, anticancer, anticoccidial, etc.
B. Antibacterial:
1. Bacteriostatic antimicrobials: Suppress bacterial growth and multiplication. E.g.: Sulphonamides, tetracyclines, chloramphenicol, erythromycin, lincomycin, etc.
2. Bactericidal antimicrobials: Cause actual death of the bacteria. E.g.: Penicillins, cephalosporins, streptomycin, kanamycin, colistin, bacitracin, nitrofurons, etc.
II. Basing on antimicrobial spectrum:
                1. Narrow spectrum: Effective against limited group of microbes.
                                a. Against Gram-positive: Penicillins, erythromycin, lincomycin, bacitracin, etc.
                                b. Against Gram-negative: Streptomycin, gentamycin, polymyxin B, etc.
2. Broad spectrum: Effective against both Gram-positive Gram-negative bacteria (e.g.: Tetracyclins, chloramphenicol, amoxicillin, cephalosporin, etc.) and sometimes more than bacteria viz., protozoa, fungai, rickettsia, etc (e.g.: Tetracyclins).
III. Basing on mechanism of action:
a.       Bacterial cell wall synthesis inhibitors: By inhibiting bacterial cell wall synthesis or causing its breakdown leading to death of the microbes. Penicillins, cephalosporins, bacitracin, etc.
b.       Cell membrane permeability modifiers: By damaging the cell membrane and thus altering the permeability causing leakage of intracellular compounds. Polymixins, colistin, nystatin, amphotericin B, etc.
c.       Protein synthesis inhibitors: By impairing protein synthesis through interfering the function of ribosomes causing reversible inhibition of protein synthesis. Tetracyclins, chloramphenicol, erythromycin, etc.
d.       By binding to the 30s ribosomal subunit and altering the protein synthesis and causing death of the bacteria. Streptomycin, neomycin, gentamycin, etc.
e.       By impairing nucleic acid metabolism:
i.                     Inhibition of DNA dependent RNA polymerase: Rifamycins.
ii.                   Inhibition of DNA supercoiling and DNA synthesis: Quinolones.
f.        By antimetabolite action through blocking specific (essential) metabolic pathways.  Sulphonamides, trimethoprim, sulfones, etc.
g.       By interfering with viral DNA synthesis and thus blocking viral replication: Ganciclovir, zidovudine, vidarabine, acyclovir, etc.

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