Lecture 3 .ppt contribution of scientists
- 1. Lecture 3 Lecture 3 Contributions – John Tyndall, Joseph Lister, Edward Contributions – John Tyndall, Joseph Lister, Edward Jenner, Robert Koch, Jenner, Robert Koch, Alexander Fleming , Selman Waksman Alexander Fleming , Selman Waksman
- 2. John Tyndall Tyndallisation (Fractional Sterilisation) Used to sterilise food/media which cannot be heated above 100°C Materilas is heated to 100°C for 15 min then allowed to cool to 37°C, where it is maintained for several hours . This will kill all vegetative cells but not spores , however the spores should germinate into vegetative cells during the 37° C wait . The material is then heated to 100°C again for 15 min. and again allowed to cool to 37°C for several hours . The subject is then heated to 100°C for a third time after which it is assumed all spores will have germinated and been killed.
- 3. Joseph Lister Joseph Lister did not discover a new drug but he did make the like between lack of cleanliness in hospitals and deaths after operations. Father of Antiseptic Surgery Lister was born in 1827 and died in 1912. ‘Ward fever’. Work on ward cleanliness and the link between germs and good post- operative health had been studied by a Hungarian doctor Ignaz Semmelweiss. He argued that if a doctor went from one patient to another after doing surgery, that doctor would pass on to the next visited patient a potentially life threatening disease.
- 4. He insisted that those doctors who worked for him wash their hands in calcium chloride after an operation and before visiting a new patient. Deaths on the wards fell from 12% to just 1%. But his findings were ignored. In 1865, Lister read about the work done by Louis Pasteur on how wine was soured. Lister believed that it was microbes carried in the air that caused diseases to be spread in wards. People who had been operated on were especially vulnerable as their bodies were weak and their skin had been cut open so that germs could get into the body with more ease. Lister decided that the wound itself had to be thoroughly cleaned. He then covered the wound with a piece of lint covered in carbolic acid. He used this treatment on patients who had a compound fracture. This is where the broken bone had penetrated the skin thus leaving a wound that was open to germs
- 5. He joined as surgeon at the Glasgow Royal Infirmary. The conditions in the hospitals in early nineteenth century were poor. .The instruments were often not even washed. Nor did the surgeon take care to wash his hands. It was not known that tiny microorganisms present in these instruments, or even from the hands of the surgeon, could cause disease, especially if there was an open wound. It was during this time that Louis Pasteur proposed his theory that microorganisms cause disease. It came as a shock to Lister that a surgeon himself was responsible for the infections in his patients, brought on as a result of poor hygiene. Carbolic acid was being used to clean foul smelling sewage. Lister performed a surgery on a small boy, he washed his hands, instruments and all that came in contact with the patient with this acid. The boy survived without any sign of infection. His technique soon revolutionized surgery as more and more patients’ lives were saved.
- 6. Edward Jenner Vaccination for smallpox. Edward Jenner was a country doctor who had studied nature and his natural surroundings since childhood. He had always been fascinated by the rural old wives tale that milkmaids could not get smallpox. He believed that there was a connection between the fact that milkmaids only got a weak version of smallpox – the non-life threatening cowpox – but did not get smallpox itself. A milkmaid who caught cowpox got blisters on her hands and Jenner concluded that it must be the pus in the blisters that somehow protected the milkmaids. James Phipps Word vaccination comes from the Latin ‘vacca’ which means cow – in honour of the part played by Blossom and Sarah in Jenner’s research.
- 7. Robert Koch Robert Koch, searched for the causes of many diseases. He and his laboratory developed many classic microbial techniques. He used adaptations of the staining methods of Carl Weigert to begin the process of distinguishing microbes and identifying pathogens. His lab was the first to isolate a disease-causing organism. Germ theory of disease (Koch's postulates) The principle of germ theory explained the cause of infectious diseases. The theory’s evolution in the 19th century was preceded by more than two centuries of observations of small life-forms under the microscope. Microorganisms were finally recognized as a cause of disease in 1876, when German bacteriologist Robert Koch proved that a bacterium was the cause of the disease anthrax. The theory’s acceptance led to improved health practices, methods of food production, sanitation, and antiseptic surgical methods, and to the practices of quarantine and immunization.
- 8. Koch Postulates - Germ theory of disease 1.The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. 2. The microorganism must be isolated from a diseased organism and grown in pure culture. 3. The cultured microorganism should cause disease when introduced into a healthy organism. 4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent. Major contributors to germ theory are: 1.Antoni van Leeuwenhoek 2.Francesco Redi 3.Rudolf Virchow 4.Louis Pasteur
- 9. A major contribution to bacterial techniques was the development of methods using solid medium. Koch was convinced that microbes caused some diseases. However, to test this idea, he needed to isolate the causative agent. Almost all samples from diseased animals or any natural surface contained many different microbes and it was impossible to tell which one was the problem. A method was needed to separate these different bacteria. The most common method of isolation was to continually dilute a sample in liquid broth in hopes that at high enough dilution, only one type of microbe would be found. A problem with this method is that only the most populous microbe would be isolated, but that might not be one causing the disease.
- 10. There were other technical problems as well with such a liquid- based system, so a solid medium would seem to provide distinct advantages. Koch had tried gelatin for these experiments with unsatisfactory results. Building on the work of Brefeld and Schroeter, Koch used potato slices as a solid medium and observed that a boiled potato left in the open air would develop tiny circular raised spots. Examination of these spots revealed they were made up of microorganisms and each spot had just one type of microbe in it. He realized that these colonies were pure cultures of bacteria and probably arose from a single species of microbe from the air that landed on the potato. By boiling a potato, slicing it with a hot knife and keeping it in a sterile container with a lid, Koch could keep the potato sterile.
- 11. But if a sample from a disease animal was smeared across the potato, colonies arose, each being pure isolates from the animal. By then testing these isolates in animals, Koch was able to isolate the cause of anthrax, Bacillus anthracis. Potatoes failed to support the growth of many microorganisms and Koch and his laboratory was constantly frustrated by the lack of a good solid medium. Walter Hesse joined Koch's laboratory to do studies on air quality, His wife, Angelina Fannie Hesse also would assist his research. Walter was attempting to do his air quality experiments using medium containing gelatin as the solidifying agent. In the summer time, temperatures would often rise above the melting point of gelatin.
- 12. In addition, microbes would often grow in the cultures that were capable of degrading gelatin and in both cases this would cause liquefaction of the medium, ruining the experiments. One day while eating lunch, the frustrated scientist asked Hesse why her jellies and puddings stayed solid even in the hot summer temp.. She told him about agar-agar, a heat resistant gelling agent that she had learned about from a Dutch neighbor who had emigrated from Java. Development of the new agent by Angelina and Walter led to a resounding success. Few microbes are able to degrade agar and it melts at 100 °C yet remains molten at temperatures above 45 °C. This allows the mixing of the agar with heat-sensitive nutrients and microbes.
- 13. After solidification, it does not melt until a temperature of 100 °C is again attained, facilitating the easy cultivation of pathogens. It can also be stored for long periods of time, allowing the cultivation of slow-growing microorganisms. Any type of broth can be mixed with agar, giving great flexibility in the kinds of medium that can be made. Thus, many more types of microbes could be cultivated. Koch's laboratory also developed methods of pure culture maintenance and aseptic technique. Another problem in the cultivation of microbes was solved by Julius Petri while working in Koch's laboratory. In 1887 Petri developed shallow glass dishes, with one having a slightly larger diameter than the other. Medium is poured into the smaller dish and the larger one serves as a cover. This simple device solved all of the above problems and took on the name of its inventor, the petri plate.
- 14. Alexander Fleming (August. 6, 1881 Darvel, Scotland to March 11, 1955 London, England) Penicillin is one of the earliest discovered and widely used antibiotic agents, derived from the Penicillium mold. Antibiotics are natural substances that are released by bacteria and fungi into the (their) environment, as a means of inhibiting other organisms . In 1928, Sir Alexander Fleming observed that colonies of the bacterium Staphylococcus aureus could be destroyed by the mold Penicillium notatum, proving that there was an antibacterial agent principle. At the time, however, the importance of Alexander Fleming's discovery was not known. Use of penicillin did not begin until the 1940s when Howard Florey and Ernst Chain isolated the active ingredient and developed a powdery form of the medicine.
- 15. Selman Waksman The first true antibiotic Waksman identified was from Actinomyces antibioticus, a member of the actinomycetes family . The microbe produced a substance, actinomycin, that had both bacteriostatic and bactericidal properties. Waksman and Woodruff determined that actinomycin could be separated with petroleum ether into two constituents, an orange-red colored actinomycin A and a colorless actinomycin B. Actinomycin A had strong bacteriostatic and bactericidal properties whereas actinomycin B displayed only bactericidal characteristics. Identified more than 20 new natural inhibitory substances, including streptomycin and neomycin, and proposed the term “antibiotics” for this class of natural growth inhibitors. Awarded Nobel Prize in physiology or medicine in 1952 “for his discovery of streptomycin - against tuberculosis.” This distinction earned him the title of “Father of Antibiotics”
- 16. The woods are lonely dark and deep But I have promises to keep And miles to go before I sleep And miles to go before I sleep - Robert Frost -