Introduction to Microbiology and Epidemiology

Quote by Louis Pasteur: "C’est les microbes qui auront le dernier mot." (It is the microbes who will have the last word).
Welcome to BIO 014, the introductory course on microbiology.

Data regarding atmospheric CO_2 levels from the years 1960 to 2000, known as the Keeling Curve, illustrates a steady increase:
- 1960: 320 \text{ ppm}
- 1970: 332 \text{ ppm}
- 1980: 350 \text{ ppm}
- 1990: 361 \text{ ppm}
- 2000: 370 \text{ ppm}
Graph Presentation:
- The x-axis represents the independent variable (Year).
- The y-axis represents the dependent variable (CO_2 levels in ppm).

Significant questions posed by early microbiologists include:
- Where does life come from?
- What causes disease?
- How are diseases transmitted?
Historical Context:
- Human history shows a profound impact of infectious diseases on society, with specific reference to:
- Smallpox: Caused by the Variola virus; responsible for millions of deaths until its eradication.
- Malaria: A mosquito-borne disease caused by Plasmodium parasites.
- Influenza: Respiratory infections that caused major pandemics, such as the 1918 outbreak.
- Bubonic Plague: Caused by Yersinia pestis, it decimated European populations in the 14th century.
Theories of disease causation:
- Miasma theory: Suggested diseases were caused by "bad air" or decaying organic matter (e.g., the term "malaria" translates to "bad air" in Italian).
- Societal beliefs: Included ideas such as witchcraft, divine retribution, and the imbalance of bodily humors (blood, phlegm, yellow bile, and black bile).

Notable contributions:
- Often called the "Father of Microbiology."
- Developed high-quality magnifying lenses to create early microscopes.
- First to observe and describe "animalcules" (microorganisms), as well as red blood cells.

Contributions:
- Published Micrographia in 1665.
- First to view and name –cells– after observing the structure of cork, which reminded him of small rooms in a monastery.

Spontaneous Generation (Abiogenesis):
- Hypothesis that living organisms arise from nonliving matter through a "vital force." This theory was widely accepted for centuries.
- Francesco Redi (1668): Challenged this by showing maggots only appeared on meat when flies could lay eggs.
Biogenesis:
- Hypothesis that living organisms arise only from preexisting living organisms.
- Rudolf Virchow (1858): Formalized the concept that all cells come from cells.

Contributions:
- Swan-Neck Flask Experiment: Decisively disproved spontaneous generation by showing that sterilized broth remained sterile unless exposed to contaminated air particles.
- Conducted research on yeast and fermentation, proving that microbes cause spoilage.
- Developed vaccines for chicken cholera, anthrax, and rabies.
- The Golden Age of Microbiology (1857-1914): A period of rapid advancement in identifying pathogens.
- Germ Theory of Disease: Highlighted the role of microbes in causing disease and spoilage, noting that:
- Certain chemicals can kill microbes.
- Infection could lead to immunity.

Recognized as the "Father of Modern Surgery."
Implemented Pasteur's ideas by introducing chemical disinfectants to reduce surgical infection rates.
Utilized carbolic acid (phenol) to clean wounds and surgical instruments, preventing sepsis.

"Father of Modern Bacteriology."
Identified specific causal agents (etiologic agents) of diseases like anthrax, tuberculosis, and cholera.
Koch’s Postulates: A framework used to establish a causal relationship between a microbe and a disease:
1. The organism must always be present in every case of the disease.
2. It must be isolated from a diseased host and grown in pure culture.
3. Samples from the culture must cause the same disease when introduced to a healthy host.
4. It must be re-isolated from the inoculated host and shown to be the same.
Exceptions to Koch's Postulates:
- Some microorganisms (like viruses) cannot be grown in pure culture.
- Different microorganisms can cause similar symptoms.
- Some pathogens cause multiple different diseases.
- Ethical restrictions on testing pathogens that only infect humans.
Molecular Koch's Postulates (Stanley Falkow, 1988): Focuses on the presence of virulence genes rather than the whole organism.

The study of the distribution, patterns, and determinants of health and disease in specific populations.
Identifies associations between health factors/behaviors (e.g., smoking, radiation) and disease outcomes.

Investigated a cholera outbreak in London, mapping cases to a single water pump on Broad Street.
Proved cholera was a waterborne disease rather than airborne.

Pioneered an epidemiological study of puerperal fever (childbed fever) in clinics.
Observed higher infection rates in clinics where doctors moved from autopsies to child delivery without washing.
Intervention: Introduced mandatory handwashing with a chlorinated lime solution.
Result: Mortality rates plummeted from over 10\% to less than 1\%.
Earned the title: "The Savior of Mothers."