Microbiology History

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Historical Aspects

Micro-organisms first seen by Antony van Leeuwenhoek in 1675 using a crude ‘microscope’ consisting of a single convex lens that had x200 magnification; Jenner in 1976 showed that smallpox could be prevented by inoculation with cowpox; Pasteur in 1867-1888 developed methods of culturing bacteria and established the principles of vaccines; Koch’s postulates in 1876 (see below); Lister (1867) – prevention of wound sepsis by antiseptic techniques

Koch’s Postulates (1876):
1. The causative organism must be present in every case of the disease and not be present in healthy cases
2. The causative organism must be isolated from diseased cases and grown in culture
3. The same disease must be produced when the causative organism is inoculated into healthy cases
4. The same causative organism must be recoverable from the inoculated cases and grown in culture

Not easy to apply these postulate to many disease states:
• Many people carry pathogens, but have no symptoms
• Some microbes can not be grown in culture (eg viruses)
• If disease is to be produced, the host must be susceptible to the pathogen
• Some diseases only develop when the host is weakened

Improved living conditions and better standards of nutrition in developed countries have lead to the conquest of epidemic and fatal infectious diseases with an increase in the life span. However infections are far from being defeated with an estimated 25% of all general medical consultations being related to infection.

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