Lecture #28

Lecture #28 - Lecture 28 Pathogenesis P h Koch's Postulates...

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11/11/2007 1 Lecture 28 Pathogenesis Koch’s Postulates Binding of Pathogens to Host Surfaces. Invasion of Host Cells by Pathogen Invasion of Host Cells by Pathogens Readings: Chapter 1.6 Chapter 21.1, 21.6-21.8, 21.14 Treat culture with a chemical mutagen or UV light Clarification of Lecture 25
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11/11/2007 2 Koch’s Postulates (Section 1.6) Applied by Koch to anthrax, tuberculosis, cholera. Limitations of Koch’s Postulates: 1. Sometimes hard to find the organism in the host (few in number, hard to stain). 2 Often “carrier” hosts exist 2. Often carrier hosts exist, healthy animals that nevertheless harbor the organism. 3. Some pathogens are obligate parasites, unable to grow outside the body. 4. Ethical limitations. Infection directly through epidermis is rare (Section 21.2, Fig 21.2). Skin is inhospitable Layers of dead skin cells at epidermis highly Skin is inhospitable. Layers of dead skin cells at epidermis, highly desiccating. Areas of high moisture encourage colonization. Most skin-colonizing bacteria are gram-positive, dessication resistant. Staphylococcus spp. (boils) Streptococcus spp. (boils) Proprionibacterium acnes (acne). Apocrine sweat glands actually encourage colonization.
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11/11/2007 3 Mechanical puncturing of skin. Puncture wounds can lead to tetanus and gangrene ( Clostridium tetani (tetatus) and Clostridum perfringens (gangrene) are soil organisms). Animal bites. Hypodermic needles Hypodermic needles. Insect transmission (see Chapter 27.3 - 27.6, but you won’t need all the
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Lecture #28 - Lecture 28 Pathogenesis P h Koch's Postulates...

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