Lecture 9 Microbiology PDF

~ Contributions of Louis Pasteur to microbiology Louis Pasteur (1822-1895) 1. Discovered the process of Fermentation. In the mid-1850s, Pasteur studied alcoholic fermentation. Pasteur demonstrated that fermentation was a process involving the action of living yea...

~ Contributions of Louis Pasteur to microbiology Louis Pasteur (1822-1895) 1. Discovered the process of Fermentation. In the mid-1850s, Pasteur studied alcoholic fermentation. Pasteur demonstrated that fermentation was a process involving the action of living yeast and that fermentation could produce lactic acid, which makes wines sour. In 1857 he presented evidence that all fermentation in milk is caused by microorganisms and that specific microorganisms cause specific kinds of fermentation. 2. Developed the process of Pasteurisation. Pasteur discovered that heating wine to 55°C degrees killed bacteria. This process named as pasteurisation delayed the onset of spoilage saving the wine industry. Pasteurisation prevents fermenting and spoilage in beer, milk, and other goods. 3. Germ theory of disease. Pasteur’s work with microorganisms in fermentation and pasteurisation led to a better understanding of germ theory - that certain diseases result from invasion of the body by microorganisms. Pasteur’s findings eventually led to improvements in sterilising and cleaning in medical practices and antiseptic methods in surgery. 13  & Germ Theory of Disease Rise of Epidemiology B. John Snow. Father of Epidemiology (1813-1858). Epidemiology deals with the cause, distribution, and control of disease in populations. John snow Investigated the cholera epidemic in 1854 in London John Snow skeptic of the then-dominant “miasma theory”. - Believed cholera transmitted by water contaminated with waste of other cholera sufferers. Used a map to plot the cases of diarrhoea in a region in London. Observed a high density of cases associated with a specific source of water (Broad Street pump). Removed the water pump (handle!!) from that source result in controlling the cholera epidemic. Successful result despite the fact the infective agent was unknown. This epidemic and its outcome disproved the Miasma theory of disease. John Snow set up standards for good public hygiene and preventing spread of infectious disease. Why is epidemiology important today? Used to; to prevent illness. 2. Guide Plan and the in whom evaluate strategies management of patients 4 disease has already developed. The Germ Theory of Disease D. Joseph Lister– Father of Modern Antisepsis 1867 - Pioneered strict asepticused carbolic surgical acid (phenol) spray (1871). Recognised that practice airborne germs responsible for surgical wound infections (50% mortality). Lister sprayed and instruments, surgical incisions (wounds) dressings with solution of carbolic acid. Lister also focused also on hand washing. His work markedly reduced the incidence of gangrene It became more accepted that infection was best. avoided by preventing bacteria from Getting into wounds in the first place. This led to the rise of sterile surgery. was 60% and was primarily caused by 1841: mortality of amputations hospital diseases 5  The Germ Theory of Disease - C. John Tyndall: (1820-1893 ) Discovered Endospores Clostridium chauvoei = that this is Blackleg Discovered that some bacteria existed in two forms: 1. Heat-stable form calledendospores 2. Heat-sensitive form - vegetative cell. Endospores need prolonged or intermittent heating to kill them. Sterilised liquid by heating it to boiling point on successive days, referred to as Tyndallisation. Gas gangrene 6  Germ Theory of Disease E. Robert Koch (Mid 1800s) Nobel Prize 1905 ~ Significance of Koch’s work: It gave experimental support to the germ theory of disease. 1. He developed media for growing bacteria in the laboratory. 2. Established a cause and effect relationship directly linking an agent to a disease. c. Working on a disease called anthrax (disease of cattle and humans) he established by careful microscopy that a spore forming bacterium (Bacillus anthracis) was always present in the blood of an animal that was becoming sick with this disease. d. He took a sample of blood from a diseased animal and injected into a healthy animal same disease symptoms and the occurred. e. presence Transferring blood from this second animal to a of theetc third spore-forming also caused the disease. Microscopy always demonstrated the organism in the bloods. f. He grew the spore-forming bacterium he had observed in blood cultures, in pure culture in the laboratory on plates and in broths (outside the animal body). g. He reintroduced the pure culture into healthy animals and demonstrated the onset of the same disease symptoms. 7 Bacteria from a diseased animal and purified in culture both caused the same  - Koch had established the “Scientific rules” to show a cause and effect relationship between a microbe and a disease. Disease: Disorder of structure or function in a human, animals, plants. KOCH’S POSTULATES (around 1884) 1. The microorganism must be always present in all hosts suffering from the disease, but absent in healthy individuals. (asymptomatic carriers, polio, hepatitis C, cholera) 2. The microorganism must be grown in pure culture away from the animal body. 3. Such a culture, when inoculated into a susceptible host should cause the characteristic disease symptoms. 4. It must be possible to re-isolate the organism from the experimental host and culture it again. It should still be the same as the original organism. Koch established the Microbial Etiology (origin) for Anthrax, Cholera and Tuberculosis. ⑭steps zodi - - 9 Know the steps - description  Limitations of Koch’s postulates ↑ (Circumstances where it wasn’t possible to use Koch’s Scientific rules to link an organism to a disease). 1. Vibrio cholerae, could be isolated from both sick and healthy people, invalidating postulate # 1 and # 3 2. Many pathogens do not cause illness in ALL infected individuals, a requirement of postulate #1. (E.g. Polio virus, Salmonella infections). (An example is poliovirus, which causes paralytic disease in about 1% of those infected). 3. Postulates # 2 and # 3 cannot be fulfilled for viruses that do not replicate in cell culture, or for which a suitable animal model for growth has not been identified. Despite their limitations Koch's postulates put the study of infectious disease on a secure scientific foundation 10 & Discovery # of antibiotics 1929 > - what is MK of antibiotics Alexander Fleming discovers penicillin. Produced by the fungus Penicillium. Fleming noticed that bacteria seemed to ‘dissolve’ when cultures were contaminated with the fungus. Not produced in major quantities until 1940s – launches the “Antibiotics Era”. Fleming is awarded the Nobel Prize in Medicine or Physiology in 1945. &