ANTIBIOTICS - AN INTRODUCTION

 ANTIBIOTICS

·   Antibiotics are the Secondary metabolites produced by the microorganisms which have the capacity to inhibit or kill the growth of another microorganisms particularly bacteria.

·       Antibiotics are low molecular weight non – protein molecules.

·       The term Antibiotic was first coined by Selman A. Waksman.

·      Penicillin was the first discovered Antibiotic. It was discovered by Alexander Fleming from the fungal Mold Penicillium notatum.

·     Streptomycin was the second discovered Antibiotic. It was discovered by Selman A. Waksman from the soil Actinobacteria Streptomyces griseus.

·    Antibiotics are used for treating Bacteria diseases only. They are not used for treating other microbial diseases.

·       Based on its spectrum of activity, Antibiotics are classified into two types. They are

a)   Broad spectrum antibiotics - The antibiotics that are effective against wide number of bacteria. Example – Streptomycin.

b)  Narrow spectrum antibiotics - The antibiotics that are effective against only limited number of bacteria. Example – Penicillin.

SOURCES OF ANTIBIOTICS

A) Antibiotics produced from Fungi

a)    Penicillin - Penicillium chrysogenum (Past) & Penicillium notatum (Present)

b)    Griseofulvin - Penicillium griseofulvum

c)    Cephalothin - Acremonium chrysogenum (Previously called Cephalosporium                                acremonium)

B) Antibiotics produced from Bacteria and Actinobacteria

a)     Vancomycin         -   Amycolatopsis orientalis (Streptomyces orientalis)

b)     Rifampin              -   Amycolatopsis rifamycinica

c)     Bacitracin             -   Bacillus licheniformis

d)     Polymyxin            -   Bacillus polymyxa

e)     Gentamycin          -   Micromonospora purpurea

f)      Mupirocin            -   Pseudomonas fluorescens

g)     Erythromycin       -   Saccharopolyspora erythraea

h)    Streptomycin        -   Streptomyces griseus

i)      Neomycin             -   Streptomyces fradiae

j)      Tetracycline          -   Streptomyces aureofaciens

k)     Chloramphenicol -   Streptomyces venezuelae

l)      Amphotericin B   -   Streptomyces nodosus

m)   Ivermectin            -  Streptomyces avermitilis

CLASSIFICATION OF ANTIBIOTICS

a)  Inhibitors of Cell wall synthesis - Bacitracin, Penicillin (Penicillin G, Penicillin V, Ampicillin and Methicillin), Isoniazid, Vancomycin and Cephalosporin.

b)    Alteration of Cell membrane - Gramicidin, Nisin, Polymyxin and Pyrazinamide.

c)  Protein Synthesis Inhibitors - Aminoglycosides (Streptomycin, Gentamycin, Kanamycin, Neomycin and Tobramycin), Chloramphenicol, Macrolides (Erythromycin, Azithromycin, Natamycin and Telithromycin) and Tetracycline.

d)    Antimetabolites - Dapsone, Sulfonamides and Trimethoprim.

e)  Nucleic acid synthesis Inhibitors - Clofaziamine, Fluoroquinolones (Ciprofloxacin), Nitroimidazoles and Rifamycin.