Germ Theory

Acceptance of germ theory highly significant for medicine Reformation of both theory and practice Immunology Antiseptic/aseptic surgery Public health Made medicine more effective

Refuting Spontaneous Generation Bacteriology began in 17th century No one knew if bacteria had a biological function Commonly believed the putrefaction (spoilage) generated bacteria

Based on older belief in spontaneous generation Mice Maggots Francisco Redi (c.1621 – c.1697) Proved maggots were not sponanteously generated

People still assumed bacteria could spontaneously generate John Tuberville Needham (1731-1781) Apparently proved this hypothesis Bacteria appeared in sterilized broth

Lazzaro Spallanzani (1729-1799) Sealed flasks after sterilizing broth No bacteria

Claimed to have disproved spontaneous generation Critics claimed all it proved was that spontaneous generation could not occur without air Debate not resolved until the 19th century

Louis Pasteur (1822-1895) Disagreed with theory of spontaneous generation Strongly influenced by his religious beliefs

Those who opposed Darwin’s theory also opposed spontaneous generation Appeared to threaten human morality Pasteur’s work in the wine industry caused him to believe that bacteria caused fermentation (not vice versa)

Pasteur was opposed by Felix Pouchet (1800-1872) Demonstrated that even carefully sterilized infusions would spoil if exposed to oxygen Declined to enter into a public contest with Pasteur

In fact, Pouchet might have won No one knew about heat resistant (spore forming) bacteria In later years, Pasteur was forced to admit that these organisms could threaten sterilizing techniques

Today, scientists believe that life did arise spontaneously on early Earth So, was Pasteur correct or not? By 1890s, spontaneous generation rejected as an explanation for putrefaction

Accepting Contagion Theory Prior to 19th century, contagion theory not accepted Some observed facts seemed to fly in face of contagion Diseases could break out in widely separated areas of the country

People who attended the sick didn’t always succumb to the disease Miasma (bad air) a common experience in crowded urban environments where disease broke out

Also evidence that supported contagion theory Sometimes attendants did get sick Outbreaks often followed trade routes

Debate divided 19th century medical community Had huge implications for disease control Quarantine Public health policy

John Snow (1813-1858) Transmission of cholera Traced 1854 outbreak to a water pump on Broad St.

Cholera transmissible in water William Budd announced similar conclusion days later Did not know what spread the illness Budd speculated that it was a fungus

Next step in acceptance of germ theory was to establish that bacteria passed from one victim to another Casimir-Joseph Davaine (1812-1882) Studied anthrax in cattle Identified large microbes in blood of infected animals

This discovery received little attention Robert Koch (1843-1910) Intrigued by Davaine’s findings

Discovered that anthrax bacteria formed spores Able to relate this finding to the epidemiological facts surrounding outbreaks Published findings in 1876; one year before Pasteur

1880: Published on bacteria found in surgical infections 1882: Discovered M. tuberculosis 1883: Dicovered V. cholerae

Success based on exceptional technical expertise Development of solid culture media .Germ theory commonly accepted by medical community

1880-1900 golden age of bacteriology New bacterial diseases identified at rate of 1/yr Gonococcus Syphilis Child bed fever Fuelled hopes that diseases such as cancer also caused by germs

Impact of Germ Theory Dramatic consequences for public health Emphasis on breaking chain of infection Discovery of healthy carriers Typhoid fever Story of typhoid Mary Germ phobia & changes in hygienic practices

Decline of the theory of predisposition

Immunology Based on the fact that living entities have immune systems Can artificially produce immunity Artificial passive immunity Artificial active immunity Smallpox & artificial active immunity already discussed

Immunology After Vaccination Several other vaccines were produced in the late 19th century Produced by manipulating organisms so that they lose virulence, but retain capacity to produce antibodies Attenuated vaccines Killed vaccines

Pasteur played significant role Accidental attenuation of chicken cholera organism Discovered it rendered chickens immune to the virulent organism Used this model to develop anthrax vaccine

Also developed rabies vaccine Pasteur criticized by some of his contemporaries and present day historians Used unproven vaccine on Joseph Meister Appropriated techniques developed by other researchers Was not completely honest about how he produced anthrax & rabies vaccine

Stakes were very high for these researchers General public desperate for solutions Koch and development of tuberculin another example

Other impacts of germ theory Impact of vaccines Mortality due to contagious diseases fell dramatically Mortality shifted to chronic diseases Other impacts of germ theory Search for specific remedies Abandonment of general therapies Reduced mortality after introduction of aseptic techniques