Infectious Diseases Unit 2 Lesson 4 plan

Do Now What is the difference between correlation and causation? How could you prove causation?

Robert Koch – connecting the dots to disease Bacillus anthracis

Identifying the infectious agent – Koch’s postulates 1.Association – It must always be present in every case – but not in healthy animals. 2.Isolation – It must be isolated from the sick animal into pure culture. 3.Causation – The pure microbe must cause the disease in a healthy animal. 4.Re-isolation - When the microbe is re-isolated from the sick animal it must be the same as the original.

Applying Koch’s postulates to cholera! 1.Association – It must always be present in every case – but not in healthy animals. 2.Isolation – It must be isolated from the sick animal into into pure culture. 3.Causation – The pure microbe must cause the disease in a healthy animal. 4.Re-isolation - When the microbe is re-isolated from the sick animal it must be the same as the original. Sack et al., 2004

Applying Koch’s postulates to cholera! 1.Association – It must always be present in every case – but not in healthy animals. 2.Isolation – It must be isolated from the sick animal into into pure culture. 3.Causation – The pure microbe must cause the disease in a healthy animal. 4.Re-isolation - When the microbe is re-isolated from the sick animal it must be the same as the original. Sack et al., 2004 Vibrio cholera

Applying Koch’s postulates to cholera! 1.Association – It must always be present in every case – but not in healthy animals. 2.Isolation – It must be isolated from the sick animal into into pure culture. 3.Causation – The pure microbe must cause the disease in a healthy animal. 4.Re-isolation - When the microbe is re-isolated from the sick animal it must be the same as the original. Vibrio cholera

Applying Koch’s postulates to cholera! 1.Association – It must always be present in every case – but not in healthy animals. 2.Isolation – It must be isolated from the sick animal into into pure culture. 3.Causation – The pure microbe must cause the disease in a healthy animal. 4.Re-isolation - When the microbe is re-isolated from the sick animal it must be the same as the original. Vibrio cholera Sack et al., 2004

Wrap up: Sometimes Koch’s postulates can’t be fulfilled! 1.Association – It must always be present in every case – but not in healthy animals*. 2.Isolation – It must be isolated from the sick animal into pure culture**. 3.Causation – The pure microbe must cause the disease in a healthy animal. 4.Re-isolation - When the microbe is re-isolated from the sick animal it must be the same as the original. *Typhoid Mary. **Leprosy or the plague.

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