Germ Theory Of Disease

The ‘germ theory of disease’ has presented a great stimulus in Microbiology and medicine. Louis Pasteur and Robert Koch (1843 – 1910) were the national heroes. Preventive measures also supported the germ theory. Edward Jenner (1796) introduced vaccination (L . vacce, cow) against small pox, using material from lesions of a similar disease of cattle (cowpox). In 1860s Joseph Lister introduced antiseptic surgery, on the basis of Pasteur’s evidence for the ubiquity of airbone microbes.

Recognition of agenes of infection: first to be recognized were fungi. Agostinod Bassi (1836) demonstrated that a fungus was the cause of disease (of silk worm), the etiologic role of bacteria was established by Koch (1876) for anthrax. The pure culture preparation is the key to the identification. Koch perfected the technique of identification including the use of solid media and the use of stain. After identifying the tubercle bacillus Koch formalized the criteria, introduced by Henle in 1840 but known as Koch’s postulates, for distinguishing a pathogenic from an adventitious microbe:

1. – The organism is regularly found in the lesion of the disease.

2. – It can be isolated in pure culture.

3. – Inoculation of this culture produces a similar disease in experiments on animals.

These criteria have proceeded invaluable in identifying pathogens, but they cannot be met: some organisms such as viruses cannot grow on artificial media and some are pathogenic only for man.

Golden era of microbiology was established between 1860 and 1910 because of development of powerful methodology. Moreover, various members of the German school isolated (in addition to the tubercle bacillus), the Cholera Vibrio, Typhoid Bacillus, Diptheria, Bacillus, Pneumococcus, Staphylococcus, Streptococcus, Meningococcus, Gonococcus and Tetanus bacillus.


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