INTRODUCTION
Antibiotics, also known as antimicrobial agents, are medications that destroy or slow down the growth of other species of microorganisms. They include a range of powerful drugs used to treat diseases caused by bacteria, fungi, actinomycetes, etc.
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The term antibiotic originates in the word antibiosis (i.e. against life). Antibiotics are chemical substances obtained from various species of microorganisms (bacteria, fungi, actinomycetes) that suppress the growth of other microorganisms and eventually may destroy them. The probable points of difference amongst the antibiotics may be physical, chemical, pharmacological properties, antibacterial spectra, and mechanism of action. They have made it possible to cure diseases caused by bacteria, such as pneumonia, tuberculosis, and meningitis, and they save the lives of millions of people around the world.
History of Antibiotics
Antibiotics began with the growing acceptance of the germ theory of disease (Louis Pasteur was one of the first recognized physicians who observed that bacteria could be used to kill other bacteria).
1871= The surgeon Joseph Lister found urine contaminated with mould could not kill the bacteria.
1890’s = German doctors Rudolf Emmerich, Oscar low made Pyocyanse from microbes. It was the first antibiotic used in hospitals but the drug did not work.
1909 = First modern chemotherapeutic agent Salvarsan for the treatment of syphilis (Paul Ehrlich).
1928 = Scottish bacteriologist Sir Alexander Fleming discovered enzyme lysozyme and the antibiotic substance penicillin.
1932 = Gerhard Domagk discovered Prontosil a prodrug.
1936 = Sulfanilamide the first synthetic sulfonamide in human medicine
1940 = Invention of Modern Drug Discovery: Ehrlich & The Magic Bullet means compound that selectively targets a disease causing organism while having no Negative effect on human tissue.
1940 = First therapeutic use of penicillin by Floury.
1944 = Selman Waksman made Streptomycin from soil bacteria.
1948 = Chlortetracycline.
1957 = Nystatin (fungal infections)
1970s = a New quinolone (pipemidic acid, oxolinic acid, cinoxacin)
1980 = Norfloxacin the first fluoroquinolone.
1980 = Enrofloxacin
1998 = Smithkline Beecham patented Amoxicillin/ clavulanate potassium
CLASSIFICATION OF ANTIBIOTICS
Antibiotics are classified based on their mechanism of action and their chemical structure.
A. Classification Based on Mechanism of Action
1. Agents that inhibit the synthesis of bacterial cell wall: These include the penicillins and cephalosporins that are structurally similar and dissimilar agents, such as cycloserine, vancomycin, bacitracin and the imidazole antifungal agents.
2. Agents that act directly on the cell membrane of the microorganisms, affecting permeability, and leading to leakage of intracellular compounds: These include polymyxin, polyene antifungal agents, nystatin, and amphotericin B that bind to cell wall sterols.
3. Agents that affect the function of 30s and 50s ribosomal subunits to cause reversible inhibition of protein synthesis: These include tetracyclines, erythromycins, chloramphenicol, and clindamycin.
4. Agents that bind to the 30s ribosomal subunit and alter protein synthesis: These include aminoglycosides that leads to cell deaths eventually.
5. Agents that affect nucleic acid metabolism: Such as rifamycins, which inhibit DNA-dependent RNA polymerase
B. Classification Based on Chemical Structure:
1. β-lactam antibiotics
2. Aminoglycoside antibiotics
3. Tetracycline antibiotics
4. Polypeptide antibiotics
5. Macrolide antibiotics
6. Lincomycins
7. Other antibiotics