Chapter15 - Definitions Chapter 15 Pathogenicity = the...

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1 Chapter 15 Mechanisms of Pathogenicity Definitions Pathogenicity = the ability to cause disease Virulence = degree of pathogenicity Measuring Pathogenicity ID 50 = infectious dose for 50% of a population LD 50 = lethal dose for 50% Legionella ID 50 = 1 cell Salmonella ID 50 = 10 5 cells Which is more virulent? Practice Problem Passengers on a plane were accidentally served water from the taps instead of bottled water. A few hours later, many of them were sick. The water was tested and found to be contaminated with 100 cfu of Shigella sonnei per ounce. What is the ID 50 of Shigella sonnei in these circumstances? Ounces of water People who drank that much water People who got sick 0 40 0 4 10 2 8 20 10 12 8 6 Questions Answered in Ch. 15 How do pathogens get into the body? How do they evade the immune system? How do they harm you? How do they move to the next host? Portals of Entry How pathogens get into the body Mostly, by mucous membranes Some go through skin
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2 Access by Mucous Membranes Respiratory tract: inhalation Cold, flu, pneumonia, TB, measles, etc. Gastrointestinal tract: ingestion
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This note was uploaded on 04/18/2011 for the course MICR 130 taught by Professor Umemoto during the Fall '09 term at University of Hawaii, Manoa.

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Chapter15 - Definitions Chapter 15 Pathogenicity = the...

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