Scientific contribution in Microbiology

SCIENTIFIC DEVELOPMENT OF MICROBIOLOGY

Scientific development of microbiology was ushered by Louis Pasteur , perfection on microbiological studies by Robert Koch , the introduction of antiseptic surgery by Lord Lister and the contributions of Pad Ehrlich in chemotherapy .

A. Louis Pasteur (1822-1895) He was a trained chemist of France. His studies on fermentation led him to take interest in microbiology, He established that fermentation was caused by microbial agents. He further noted that different types of fermentations were associated with different kinds of microorganisms . He is also known as father of microbiology.

Important Contributions of Louis Pasteur in Microbiology

1. Development of methods and techniques of bacteriology.

2. Proved conclusively that all forms of life , even microbes , arose only from their like and not de novo . 3. Pasteur also had to face challenge from Pouchet, who was a proponent of spontaneous generation theory of microbe. Pasteur disproved the view by demonstrating the ubiquity of microorganisms in the air by his experiments performed in the swan-necked flasks.

4. Introduction of sterilization techniques and development of steam steriliser, autoclave and hot air oven.

5. Studies on anthrax, chicken cholera and hydrophobia. During studies on rabies , though Pasteur could not isolate any microorganism from man and dog but suggested that the causative agent of rabies was too small to be seen by microscope .

6. Live vaccine : He introduced attenuated live vaccine for prophylactic use. An accidental observation that chicken cholera bacillus cultures left for several weeks lost their pathogenicity but retained their ability to protect the birds against subsequent infection by them led to the concept of attenuation and development of live vaccines. He attenuated the anthrax bacillus by incubation at high temperature ( 42–43 °C ) and proved that inoculation of such bacilli in animals induced specific protection against anthrax . He convincingly demonstrated the protective role of anthrax vaccine in a public experiment (1881) where vaccinated sheep, goats and cows were challenged with a virulent anthrax bacillus culture. All the vaccinated animals survived while an equal number of unvaccinated control animals died . Pasteur coined the term vaccine for such prophylactic preparations to commemorate the first of such preparations , namely , cowpox , employed by Jenner for protection against smallpox . Pasteur's development of a vaccine for hydrophobia marked a milestone in development of immunization in medicine. He obtained the fixed virus of rabbits by serial intracerebral passage in rabbits. The rabies vaccine was prepared by drying pieces of spinal cord from rabbits infected with fixed virus. This work was acclaimed throughout the world. The Pasteur Institute , Paris , was built by public contribution for the preparation of vaccines and for the investigation of infectious diseases .

B. Joseph Lister (1827–1912)

He was a Professor of Surgery in Glasgow Royal Infirmary. He applied Pasteur's work and introduced antiseptic techniques in surgery (1867) effecting a pronounced drop in mortality and morbidity due to surgical sepsis. It was a milestone in the evolution of surgical practice from the era of ' laudable pus ' to modern aseptic techniques. His antiseptic surgery involved the use of carbolic acid. He is known as father of antiseptic surgery.

C. Robert Koch (1843–1910)

Robert Koch was a German general practitioner. He is also known as the father of bacteriology. His contributions are as follows:

1. Perfected bacteriological techniques and introduced methods for isolation of pure strains of bacteria.

2. Introduced methods of obtaining bacteria in pure cultures using solid media.

3. Introduced staining techniques.

4. Discovered the anthrax bacillus (1876), tubercle bacillus (1882) and the cholera vibrios (1883).

5. Koch's postulates : According to Koch's postulates , a microorganism can be accepted as the causative agent of an infectious disease only if the following conditions are fulfilled. (i) The organism should be constantly associated with the lesions of the disease.

(ii) It should be possible to isolate the organism in pure culture from the lesions of the disease.

( iii ) The isolated organism ( in pure culture ) when inoculated in suitable laboratory animals should produce a similar disease .

(iv) It should be possible to re-isolate the organism in pure culture from the lesions produced in the experimental animals.

An additional criterion introduced later requires that specific antibodies to the organisms should be demonstrable in the serum of patients. These postulates have proved to be useful in confirming doubtful claims made regarding the causative agents of infectious diseases. However, it may not always be possible to satisfy all the postulates in every case. An important example of not fulfilling the Koch's postulates is lepra bacillus.

6. Koch's phenomenon: Robert Koch observed that guineapigs already infected with tubercle bacillus responded with an exaggerated inflammatory response when injected with the tubercle bacillus or its protein. This hypersensitivity reaction is called Koch's phenomenon.

D. Paul Ehrlich ( 1854-1915 )

Paul Ehrlich was a German scientist and is also known as father of chemotherapy . His contributions are as follows:

1. Applied stains to cells and tissues for study of their functions.

2. Reported the acid - fast nature of tubercle bacillus.

3. Proposed ' side chain theory ' of antibody production.

4. Discovered salvarsan, an arsenical compound, sometimes called the ' magic bullet '. It was capable of destroying the spirochaete of syphilis. Later on he discovered ' neosalvarsan ' and thus created a new branch of medicine known as chemotherapy.

5. Introduced methods of standardizing toxin and antitoxin.

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