Antibiotics PDF

 History  Chemotherapy as a science began with Paul Ehrlich in the first decade of this century.  Ehrlich received the Nobel Prize for Medicine in 1908.  In 1906 he discovered the structural formula of atoxyl, a chemical compound which had been shown to be able t...

 History  Chemotherapy as a science began with Paul Ehrlich in the first decade of this century.  Ehrlich received the Nobel Prize for Medicine in 1908.  In 1906 he discovered the structural formula of atoxyl, a chemical compound which had been shown to be able to treat sleeping sickness (trypanosomiasis).  In 1909 he and his student Sahachiro Hata developed Salvarsan (arsphenamine), a treatment effective against syphilis. Continue  Gerhard Domagk was a German pathologist and bacteriologist recognized with the discovery of the first commercially available antibiotic (marketed under the brand name Prontosil).  In 1939, he received the Nobel Prize in Medicine for this discovery, the first drug effective against bacterial infections (streptococcal infections ).  Prontosil decomposes in the living body to give a highly active sulphonamide and the toxic compound thiaminobenzene. Continue  The 'golden age' of antimicrobial therapy began with the production of penicillin.  This was discovered by Sir Alexander Fleming (1929) who noticed that the growth of staphylococci was inhibited round a mould of Penicilian notatum which was growing by accident on a culture plate.  From this mould, penicillin was extracted and mass produced in 1940 by the work of Florey & Chain.  He shared the Nobel Prize in physiology and Medicine in 1945 with Howard Florey and Ernest Chain. Continue  Antibiotics = a natural substance produced by a micro-organism to kill another.  Anti-infectives / Anti-microbrial = any agent (natural or synthetic) that kills pathogens (microbes). Classification of antibiotics l antibacterial  According to their origin (sources)  According to their chemical structure According to the spectrum of their  biological action  According to their mode of action   According to their origin (sources) Microorganisms Bacteria Synthetic antibiotics Fungi Actinomycetes Semi synthetic antibiotics Examples of Microbial Sources of Antibiotics Streptomyces   According to their chemical structure b. Aminoglycosides and a. Beta-lactam antibiotics Aminocyclitols c. Chloramphenicol d. Tetracyclines e. Polyenes f. Macrolides  a. Beta-lactam antibiotics  β-Lactam antibiotics are a broad class of antibiotics, consisting of all antibiotic agents that contains a β-Lactam nucleus in its molecular structure.  It includes penicillins, cephalosporins, and cephmycins. Continue  b. Aminoglycosides  An aminoglycoside is a molecule or a portion of a molecule composed of amino-modified sugars.  They are glycosidic derivatives of streptamine.  Both streptomycin and dihydrostreptomycin contain streptidin and aminosugars in their structure, while other members containing deoxystreptamine and amino sugar in their structure e.g. neomycin, kanamycin, tobramycin, amikacin, and gentamicin.  Aminoglycosides that are derived from bacteria of the Streptomyces genus are named with the suffix -mycin, whereas those that are derived from Micromonospora are named with the suffix –micin. Continue  Aminocyclitols  It is a closely related group to aminoglycosides.  These contain no amino sugar in their structure e.g. spectinomycin.  d. Tetracyclines  A family of closely related antibiotics with four-ringed structure e.g. tetracycline, chlorotetracycline, oxytetracycline, demeclocycline, methacycline, doxycycline and minocycline.  e. Polyenes  These are characterized by possessing a large ring containing a lactone group and a hydrophobic region consisting of a sequence of 4-7 conjugated double bonds.  Polyenes are poly-unsaturated organic compounds that contain one or more sequences of alternating double and single carbon-carbon bonds, e.g. nstatin, amphotericin. Continue  f. Macrolides  These consisting of a macrocyclic lactone ring to which sugars are attached.  They include erythromycin, oleandomycin and spiramycin.   According to the spectrum of their biological action a. Antibacterial antibiotics b. Antifungal antibiotics c. Antitumor antibiotics d. Antiprotozoal antibiotics e. Antiviral antibiotics  a. Antibacterial antibiotics Narrow spectrum  Natural penicillins and erythromycin (G +ve)  Polymyxin (G –ve). Broad spectrum  Effective against at least some members of most genera  Tetracyclines and chloramphenicol. Tuberculostatic Streptomycin, kanamycin and cycloserine.  Nystatin, amphotericin B, b. Antifungal antibiotics griseofulvin, and candicin. c. Antitumor antibiotics Actinomycins, mitomycins. d. Antiprotozoal antibiotics  Fumagillin. e. Antiviral antibiotics  Helinine.   According to their mode of action b. a. Inhibitors of cell wall b. Antibiotics acting on cell synthesis membranes c. Inhibitors of protein d. Inhibitors of nucleic acid synthesis synthesis e. Inhibitors of folic acid synthesis (antifolates) a. Inhibitors of cell wall synthesis Continue Continue  The steps of biosynthesis involves many essential enzymes: I. Racemes (catalyze change of L-alanine to D-alanine). II. Synthetase (join two D-alanine molecules forming the terminal D-alanyl-D-alanine residue of the penta peptide). III. Transpeptidases (catalyze transpeptidation or cross-linking reactions). Continue  Penicillins.  Cephalosporins.  Bacitracin.  Vancomycin.  Teicoplanin.  Cycloserine.