Germ Theory

1. Germ Theory

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

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

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

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

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

7. 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

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

9. 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)

10. 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

11. 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

12. 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

13. 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

14. 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

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

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

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

18. 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

19. 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

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

21. 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

22. 1880: Published on bacteria found in surgical infections • 1882: Discovered M. tuberculosis • 1883: Dicovered V. cholerae

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

24. 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

25. 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

26. Decline of the theory of predisposition

27. 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

28. 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

29. 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

30. 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

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

32. 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