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http://faculty.ksu.edu.sa/manalk/Pages/460MIC.aspx Medicines and Drugs 6 Antibacterial Drugs (SL + HL) 1 D6 Antibacterials - Assessment Statements D.6.1 Outline the historical development of penicillins. D.6.2 Explain how penicillins work and discuss the effects of modifying the side-chain. Also see D.8.3 (HL students). D.6.3 Discuss and explain the importance of patient compliance and the effect of penicillin overprescription. 2 Bacteria - Background Some Pathogenic Bacteria Neissera gonorrhea Staphylococcus Vibrio cholerae Salmonella Syphilis 3 Bacteria - Background Bacterial Structure There are many types of bacteria, with varying structures. These features are common to most bacteria: unicellular target of many antibiotics ! http://geneticssuite.net/node/11 4 Bacteria - Background Mode of Action of Pathogenic Bacteria bacteria release chemicals called toxins into the blood and tissues toxins act on different target organs to disrupt cell processes e.g. tetanus (lockjaw) and Salmonella 5 Antibacterials aka antibiotics inhibit the growth of bacteria http://www.accessexcellence.org/AE/AEC/CC/s1.php specifically inhibit bacterial cell growth and not human cell growth Attack! ✗ 6 Antibacterials Early Antibiotics sulfonamides the first antibacterial drugs “sulfa drugs” used in the dye industry effective treatment of septicemia from early 1930s 7 Antibacterials “Modern” Common Antibiotics naturally produced by certain molds now synthesized in laboratories penicillin G and penicillin V ampicillin amoxycillin tetracycline erythromycin 8 Discovery and Development of Penicillin The Discovery! one of the greatest revolutions in medicine Alexander Fleming Scottish microbiologist and WWI veteran studied the infectious bacterium Staphylococcus aureus in 1928 in London http://en.wikipedia.org/wiki/Alexander_Fleming noticed many of the culture plates became contaminated with mold and was ready to throw them away ! 9 Discovery and Development of Penicillin The Discovery! serendipity closer observation revealed that there was a clear zone around the mold no bacteria grew near the mold Fleming concluded that something produced by the mold inhibited bacterial growth. mold = Penicillim notatum ! published a paper and then stopped could not isolate the active compound Chemistry fail? 10 Discovery and Development of Penicillin Development of the Drug ! 1940 ... enter Florey and Chain We know Chemistry! worked at Oxford to isolate the active ingredient from the Penicillin notatum mold injected the isolated compound into infected mice high survival rate 11 Discovery and Development of Penicillin Development of the Drug WW II need for a drug to combat battle wounds further drug development moved to the US large batch production of penicillin in corn-steep liquor in fermentation tanks 1945 Nobel Prize in Medicine awarded to Fleming, Florey and Chain 12 How Penicillin Works General Structure of Penicillin There are several types of “penicillin” extracted from the Penicillin notatum mold. They all have this basic structure: ! Identify four structural features. carboxyl group 2º amide beta lactam ring R group 13 How Penicillin Works Different Penicillin Structures There are several types of “penicillin” extracted from the Penicillin notatum mold. ! penicillin V R GROUP ! amoxicillin ! penicillin G ! ampicillin 14 How Penicillin Works Different Penicillin Structures What is the effect of changing the R-group? 1. no change to the beta lactam ring The beta lactam ring is responsible for the activity of penicillin. 2. it may change the properties of the drug Penicillin G is broken down by the stomach. How must it be administered? Penicillin V is not broken down by the stomach. How must it be administered? 3. it may improve the resistance of the drug Ampicillin is not as likely as penicillin G or V to be broken down by the enzymes in some bacterial strains. 15 How Penicillin Works Mechanism of Action penicillin blocks the synthesis of peptidoglycan (a component of the bacterial cell wall) The cell wall is weakened. Water can move into the cell and the bacterium lyses and dies. Penicillin is a bacteriocidal antibiotic. Penicillin does not attack human cells because human cells do not have cell walls (i.e. no peptidoglycan) 16 Antibiotic Use, Overuse and Misuse Antibiotics ONLY act against bacteria ... NOT viruses. 1. antibiotics are over-prescribed may kill the helpful bacteria in your intestinal tract harmful bacteria may replace them 17 Antibiotic Use, Overuse and Misuse 2. patients do not follow the complete course of treatment = noncompliance some harmful bacteria survive contributes to development of resistance 3. antibiotics are available in some parts of the world without a prescription people self medicate leads to overuse & development of resistance 4. wide use of antibiotics in feedstock 70 - 80% of all antibiotic use enters food products 18 Antibiotic Resistance Some bacteria have an enzyme called penicillinase. breaks down pe n icillin bacteria are resistant to the antibiotic Chemists try to develop new antibiotics which are not broken down by bacterial enzymes. modify the R group 19 Antibiotic Resistance natural selection When a bacterial population is exposed to the antibiotic over a long period of time, the ones without resistance die. However, if there are resistant bacteria, they survive and reproduce. Over long periods of time, the remaining bacteria will now be resistant. They cannot be treated with the original antibiotic, and new antibiotics must be used (or developed). 20