Immunology/Germ Theory

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 (17311781) – Apparently proved this hypothesis – Bacteria appeared in sterilized broth







Lazzaro Spallanzani (17291799) 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

century

not resolved until the 19th







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

morality

 Pasteur’s

to threaten human

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,  By

was Pasteur correct or not?

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  Outbreaks

routes

attendants did get sick

often followed trade

 Debate

divided 19th century medical community

 Had

huge implications for disease control – Quarantine – Public health policy







John Snow (18131858) 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

 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