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Pharmacology and development of Antibiotics (Penicillin) and Antiseptics 13/02/13 By: Mohit Kumar Sharma PhD Final year Slide 2 Eukaryotic cellProkaryotic cell Cell types Slide 3 Slide 4 Slide 5 Bacterial classification based on Gram staining Slide 6 Gram staining technique Slide 7 Gram positive Gram negative Bacterial classification based on Gram staining Slide 8 Slide 9 Peptidoglycan Slide 10 Transpeptidase cross-linking to peptidoglycan sheets Slide 11 Slide 12 Few Examples of different classes of Bacteria Slide 13 Slide 14 - Skin - Tears - Saliva - Stomach acid Protection against bacteria Slide 15 Skin The skin is tough, dry, salty, oily, rich in fatty acids and urea, low in nutrients (lots of dead, empty cells) & thick. The sweat glands secrete a mixture of salt & fatty acids that inhibit many microbes. Slide 16 Tears Lysozyme is an enzyme, present in tears that LYSES many prokaryotic cells by digesting the peptidoglycan in their cell walls. - Through hydrolysis of glycosidic linkages. Slide 17 Saliva There is a continuous flow of fluid (saliva) through the mouth which FLUSHES loose microbes into the stomach. Stomach acid The stomach contains a strong (hydrochloric) acid. Many microbes are killed by this acidic environment and digested by the proteolytic enzymes in the digestive system. Slide 18 What are Antibiotics? - Antibiotics, also known as antibacterials, are types of medications that destroy or slow down the growth of bacteria. - The term antibiotic was first used in 1942 by Selman Waksman - The Greek word anti means "against", and bios means "life" (bacteria are life forms). - Many antibacterial compounds are relatively small molecules with a molecular weight of less than 2000 atomic mass units - The first antibiotic was penicillin. - Penicillin-related antibiotics such as ampicillin, amoxicillin and benzylpenicilllin are widely used today to treat a variety of infections. Slide 19 How do antibiotics work? Although there are a number of different types of antibiotic they all work in one of two ways: - A bactericidal antibiotic kills the bacteria. Penicillin is a bactericidal. A bactericidal usually either interferes with the formation of the bacterium's cell wall or its cell contents. - A bacteriostatic stops bacteria from multiplying. Slide 20 Targets of Antimicrobials 1. Cell wall inhibitors Block synthesis and repair Penicillins Cephalosporins Carbapenems Vancomycin Bacitracin Fosfomycin Isoniazid 2. Cell membrane Causelossofselective permeability Polymyxins Daptomycin 3. DNA/RNA Inhibit replication and transcription Inhibit gyrase(unwinding enzyme) Quinolones Inhibit RNA polymerase Rifampin Ribosome mRNADNA 4. Protein synthes is inhibitors acting on ribosomes Site of action 50S subunit Erythromycin Clindamycin Synercid Pleuromutilins Site of action 30S subunit Aminoglycosides Gentamicin Streptomycin Tetracyclines Glycylcyclines Both 30S and 50S Blocks initiation of protein synthesis Linezolid 5. Folic acid synthesis Block pathways and inhibit metabolism Sulfonamides (sulfa drugs) Trimethoprim Substrate Enzyme Product Slide 21 Mechanisms of Drug Action Inhibition of cell wall synthesis Inhibition of nucleic acid structure and function Inhibition of protein synthesis Interference with cell membrane structure or function Inhibition of folic acid synthesis Slide 22 Penicillin Slide 23 Alexander Fleming - 1928, Alexander Fleming - Observed antibiosis against bacteria by a fungus of the genus Penicillium. - 1940, Florey and Chain - Began work on isolating and synthezing large amounts of Penicillin. - 1940, Preclinical trials in mice - 1941, Phase II Clinical trial - 1944 - Used in WWII to treat infections - Late 1940s - available for general use in US History of Penicillin Slide 24 Staphylococcus aureus (bacterium) Penicillium chrysogenum (fungus) Zone where bacterial growth is inhibited Antibiotic effect of the mold Penicillium chrysogenum Slide 25 Penicillin Source: Penicillin chrysogenum Penicillin antibiotics grouped into generations based on spectrum of anti-microbial activity. (1 st, 2 nd, 3 rd and 4 th generations) Natural (penicillin G and V) Semisynthetic (Ampicillin, Carbenicillin) Slide 26 Classification Penicillins (penicillin G) greatest activity against gram+, gram-cocci, non-beta-lactamase-producing anaerobes Antistaphylococcal penicillins (nafcillin) resistant to staphylococcal beta-lactamases, active to staphylococci and streptococci Extended-spectrum penicillins (ampicillin) retain antibacterial spectrum of penicillin with improved activity against gram- organisms, but are destroyed by beta-lactamases. Slide 27 Types of Penicillin Slide 28 Chemical Structure Penicillins as well as cephalosporins are called beta-lactam antibiotics, characterized by 3 fundamental structural requirements: the fused beta-lactam structure a free carboxyl acid group one or more substituted amino acid side chains Slide 29 Slide 30 - The R group is responsible for the activity of the drug and can be changed to improve activity of the antibiotic. - Cleavage of the beta-lactam ring will render the drug inactive. Chemical structure of penicillins Structure Thiazolidine ring Beta-lactam ring Variable side chain (R group)