抗生素PPT课件（英文精品）_1.ppt

Bacterial conjugation * ANTIBIOTIC PROBLEM there are many chemicals that are lethal to bacteria (e.g. cyanide), but cannot be used to cure because they are lethal to the host as well problem is to find substances that attack a metabolic pathway found in bacterium but not in host SOLUTION Natural products originally discovered as secretions of fungi or soil bacteria Semi-synthetic products natural products chemically modified in laboratory to improve efficacy of natural product, reduce its side effects Completely synthetic products Treatment of bacteria diseases first known use of antibiotics - ancient Chinese (2,500 years ago) ancient Egyptians and Greeks used molds and plants to treat infections Antibiotics Definition: chemotherapeutic agent that inhibits or stop the growth of micro-organisms (bacteria, fungi or protozoans) small molecules with a molecular weight less than 2 kDa Term Antibiotic first used for substances extracted from fungus or other microorganism now used also for synthetic and semi-synthetic drugs with antibacterial effects Other informations – animated: /biointeractive/Antibiotics_Attack/frameset.html first produced and isolated from living organisms: - fungi Penicillium – antibiotic penicillin - bacteria Streptomyces – antibiotic streptomycin then obtained by chemical synthesis – antibiotic sulfa drugs Penicillin discovered from the fungus Penicillium notatum in 1928 by Alexander Fleming Alexander Fleming 6.8.1881 (Scotland) – 11.3.1955 (England) Fields: bacteriology, immunology Nobel Prize in Physiology or Medicine in 1945 Fleming receiving the Nobel prize from King Gustav V of Sweden (right), 1945 Accidental discovery On 3 September 1928, Fleming returned to his laboratory having spent August on vacation with his family. Before leaving he had put his cultures of staphylococci in a corner of his laboratory. On returning, Fleming noticed that one culture was contaminated with a fungus, and that the colonies of