L38 - Microbes and disease [2016.09.28].pdf

L38 - Microbes and disease [2016.09.28].pdf - 1 MICROBES...

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1 MICROBES AND DISEASE I. INTRODUCTION AND DEFINITIONS Microbiology is the study of organisms which are usually small in size, simple in structure (and neither plants nor animals except in the case of algae and parasites). Microbes (micro-organisms) can be classified as VIRUS, BACTERIA, FUNGUS, PROTOZOA (PARASITES) and PRIONS by their size, culture conditions, cell wall or nuclear structures and others. Clinical microbiology is the study of the effects of microbes on human as a pathogen (disease causing organism) or/and commensal (colonising organism) at the laboratory and the bedside. It concerns with the diagnosis, management and control of infectious disease. Infectious diseases are diseases caused by microbes and are often communicable/ spread by direct or indirect contact (concept of contagion ), and other ways of exposure. Thus unlike other human diseases, many infectious diseases ( communicable disease ) can cause massive outbreaks ( epidemics or pandemics ) and the associated terror or social stigmatisation. IMPORTANT HISTORICAL LANDMARKS 1. In 1673, Antoine van Leeuwenhoek, a Dutch lens-maker devised a microscope and accurately describe the morphology of bacteria, yeast (a form of fungus) and protozoa. 2. In 1844, Louis Pasteur, a chemist, proved that micro-organisms can produce stereoisomeric forms of tartaric acid and amyl alcohol by fermentation of sugars. Such isomers did not spontaneously arise from purely chemical decomposition of sugar. Particular micro-organisms recognisable by their morphology and growth requirements can produce different fermentation products. His results supported the GERM THEORY proposed by Henle in 1840. By a series of elegant experiments, the concept of pathogenesis of infection related to bacterial fermentation inside animals (human) was conceived, and thus putrefaction of dead bodies is the bacterial fermentation in the corpse, and the concept of sterilisation by heat which kills microbes were founded. The concept of communicable disease and its control by isolation (quarantine) was conceived when Louis Pasteur investigated an outbreak of diseases in the silkworm industry. He stopped the epidemic in silkworm by segregating and propagating the healthy silkworm away from those with early features of disease. 3. In 1867, Joseph Lister, a surgeon applied the knowledge of Pasteur in surgical operations and started the aseptic technique for surgical procedures. It was a major success and transformed the prognosis of major surgical operations . 4. Between 1876 to 83, Robert Koch, a country physician successfully demonstrated the pathogenicity of Bacillus anthracis in causing a deadly disease called anthrax in animals. He also devised the isolation of pure bacterial species on solid culture medium by streaking of agar plate , and the method of staining of bacteria by dye .
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