A plethora of observant researchers had already conceptualized and opined rather vehemently
the much applauded and widely accepted ‘germ theory’ of disease even before Pasteur established
experimentally that microbes (or bacteria) happen to be the root cause of several human dreadful
diseases. Later on various other scientists supported and proved the aforesaid ‘germ theory’ in one way
or the other as stated under :
Girolamo Fracastro (1483–1553) : advocated that certain diseases might be caused by virtue of
invisible organisms transmitted from one subject to another.
Plenciz (1762) : stated that the living microbes (or agents) are the ultimate cause of disease but
at the same time aired his views that different germs were responsible for different ailments.
Oliver Wendell Holmes (1809–1894) : suggested that puerperal fever** was highly contagious
in nature ; besides, it was perhaps caused by a germ carried eventually from one mother to another
either by midwives or physicians.
Ignaz Philipp Semmelweis (1818–1865) : pioneered the usage of antiseptics specifically in the
obstetrical practices.
Joseph Lister (1890) : made known in England the importance of antisepsis, which was subsequently
fully appreciated by the medical profession all and sundry.
Robert Koch (1843–1910) : discovered the typical bacilli having squarish ends in the blood
sample of cattle that had died due to anthrax.*
Koch’s Modus Operandi — Koch adopted the following steps to isolate microbes causing anthrax
:
(1) First of all these bacteria were duly grown in cultures in the laboratory.
(2) Bacteria examined microscopically so as to ascertain only one specific type was present.
(3) Injected bacteria into other animals to observe whether they got also infected, and subsequently
developed clinical symptoms of anthrax.
(4) Isolated microbes from experimentally infected animals squarely matched with those obtained
originally from sheep that died due to infection of anthrax.
Koch’s Postulates : The series of vital observations ultimately led to the establishment of Koch’s
postulates, that essentially provided four vital guidelines to identify the particular causative agent for an
infectious disease, namely :
(a) A particular microbe (organism) may invariably be found in association with a given disease.
(b) The organism may be isolated and cultivated in pure culture in the laboratory.
(c) The pure culture shall be able to cause the disease after being duly inoculated into a susceptible
animal.
(d) It should be quite possible to recover conveniently the causative organism in its pure culture
right from the infected experimental animal.
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