Microbiology and Immunology

History of Public Health WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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the organism in pure culture. While limiting dilutions could

have been used (as described previously by Joseph Lister,

1827–1912), Koch promoted the use of solid media, giving

rise to separate colonies and the use of stains. In 1882, Koch

identified the tubercle bacillus and so formalized the criteria

of Henle for distinguishing causative pathogenic microbes.

This set of criteria is known as Koch’s postulates.

One of the most important applied developments in

microbiology was in understanding the nature of specific

acquired immunityto disease. That such immunity was possi-

ble was known for a long time, and the knowledge finally

crystallized with the prophylactic treatment for smallpox

introduced by Edward Jenner(1749–1823). Using cowpox,

Jenner introduced the first vaccination procedures in 1796.

This occurred long before the germ theory of disease had been

established. Later workers developed additional methods of

increasing the immunity of an individual to disease, but the

most dramatic triumph was the discovery of the diphtheriaand

tetanusantitoxins by von Behring and Kitisato in the 1890s.

This work later developed into a practical tool by Paul Ehrlich

(1854–1915) and it was now possible to cure a person suffer-

ing from these diseases by injecting some antitoxic serum pre-

pared by earlier immunizationof a horse or other large animal.

This led for the first time to rational cures for infectious dis-

eases, and was responsible for Ehrlich’s later conception of

chemotherapy. The antibiotics era, which followed the

groundbreaking work of Alexander Fleming(1881–1955) with

penicillin, was another important step in the understanding of

microbiology.

Most of the most recent work in the development of

microbiology has been in the field of microbial geneticsand

how it evolved into a separate discipline known as molecular

biology. This work really began in the 1940s, when Oswald

Avery, Colin MacLeodand Maclyn McCartydemonstrated that

the transforming principle in bacteria, previously observed by

Frederick Griffiths in 1928, was DNA. Joshua Lederbergand

Edward Tatumdemonstrated that DNA could be transferred

from one bacterium to another in 1944. With the determination

of the structure of DNA in 1953, a new and practical aspect of

microbiology suddenly became realised, and the foundations

of genetic engineering were laid. It is perhaps important to

realize that if it were not for bacteria and their characteristics,

genetic engineering would not be possible. The concept of

DNA transfer was essentially born in the 1940s. Later on, in

the late 1960s bacterial restriction enzymeswere discovered

and the possibilities of splicing and rearranging DNA

emerged. The advances in molecular biology following these

major breakthroughs have been immense but it is important to

realize that the field of microbiology lies at their root.

See also Antibiotics; Fermentation; Microscope and

microscopy; Vaccine

HHistory of Public HealthISTORY OFPUBLICHEALTH

Infections caused by microorganismsare often spread more

easily in an unsanitary environment. Even today, for example,

Escherichia coliinfections of food and between people are

still commonly caused by poor hygienic practices, such as the

failure to properly wash hands after toileting.

Because of the association between microbial infection

and sanitary conditions, many public healthinitiatives and

regulations have been instituted around the world. Before the

recognition that microbes caused infections, and even before

the realization that microbes existed, public health was a for-

eign concept. The history of public health parallels advances

in the understanding of microorganisms and disease.

Prior to the fourteenth century, public health was nonex-

istent. The sanitary environment in urban centers was appalling

by today’s standards. However, at that time there was no

knowledge that, for example, the flow of raw sewage alongside

streets was connected to illness. The occurrence of bubonic

plaguein Europe in 1348 began to change this view. Between

1348 and 1350, the infection caused by Yersinia pestiskilled

almost two-thirds of the population in the major urban centers

of Europe. In the aftermath of this devastation came an

increased awareness of the influence of health conditions and

disease. In the 1350s, Italian government initiatives sought to

improve sanitary and living conditions. These initiatives

occurred even though the existence of microorganisms was not

Robert Koch in his laboratory in the late nineteenth century.

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