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Unformatted text preview: Antonio Alarcon MIC 205 Study Guide #3 11/03/07 • Antimicrobial Drugs o Ehrlich’s Magic Bullets Ehrlich coined the term " chemotherapy " and popularized the concept of a " magic bullet ". He is credited with the first empirical observation of the blood-brain barrier and the development of the first antibiotic drug in modern medicine ( Salvarsan ) o Fleming and Penicillin Fleming was the first to notice the antibiotic properties of moulds and fungi.By 1928, he was investigating the properties of staphylococci . He was already well-known from his earlier work, and had developed a reputation as a brilliant researcher, but quite careless lab technician; cultures that he worked on he often forgot, and his lab in general was usually in chaos. After returning from a long holiday, Fleming noticed that many of his culture dishes were contaminated with a fungus and he threw the dishes in disinfectant. But on one occasion, he had to show a visitor what he had been researching, and so he retrieved some of the unsubmerged dishes that he would have otherwise discarded, when he then noticed a zone around an invading fungus where the bacteria could not seem to grow. Fleming proceeded to isolate an extract from the mould, correctly identified it as being from the penicillium family, and therefore named the agent penicillin . o Chemotherapy The use of drugs to treat a disease Selective toxicity : A drug that kills harmful microbes without damaging the host o Antibiotic/Antimicrobial Antibiotic : Chemical produced by a microorganism that kills or inhibits the growth of another microorganism Antimicrobial agent : Chemical that kills or inhibits the growth of microorganisms o Antibiotic Spectrum of Activity No antibiotic is effective against all microbes o Mechanisms of Antimicrobial Action Bacteria have their own enzymes for Cell wall formation Protein synthesis DNA replication RNA synthesis Synthesis of essential metabolites o Mechanisms of Antimicrobial Action Viruses use host enzymes inside host cells Fungi and protozoa have own eukaryotic enzymes The more similar the pathogen and host enzymes, the more side effects the antimicrobials will have o Modes of Antimicrobial Action Inhibition of: • Cell wall synthesis • Protein synthesis • Nucleic acid replication and transcription • Injury to plasma membrane • Synthesis of essential metabolites o Antibacterial Antibiotics: Inhibitors of Cell Wall Synthesis Penicillin (over 50 compounds) • Share 4-sided ring ( lactam ring) Natural penicillins • Narrow range of action • Susceptible to penicillinase (...
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- Fall '07