Bio2051ch25 - Chapter25 Chapter25MicrobialPathogenesis

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Chapter 25   Chapter 25 Microbial Pathogenesis   Host-Pathogen Interactions Infection = ENTRY OF PARASITE OR PATHOGEN INTO HOST  Infection doesn’t always cause disease  Most infections removed by immune disease  Primary pathogens  Have ability to penetrate host defenses  Opportunistic pathogens  Cause disease only in compromised host  Immune system defective  Break in tissue allows organism access to new site  Loss of other microflora allows organism to bloom  Pathogenicity of organism  Measure of ability to cause disease  Determined by genetic makeup of organism  Infectious dose = ID50  Number of organisms to colonize 50% of hosts  Virulence  Rate of lethal infections  Lethal dose = LD50  Number of organisms to kill 50% of hosts Infection Cycle  Spread by direct contact  Spread by indirect contact  Contact with fomites - inanimate objects that carry infectious microbes   Horizontal transmission via vectors (organism)  Mosquitoes - yellow fever, malaria   Reservoir for disease organism  1
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May not show disease symptoms  Mode of entry depends on pathogen  Mucosal surfaces, wounds, insect bites   Virulence Factors Virulence genes Encode factors allowing pathogen to invade host  Toxins, attachment proteins, capsules   Pathogenicity   Section of genome  Contain multiple virulence genes  Often encode related functions  E.g., protein secretion system, toxin production  Transferred as a block from other organisms   Virulence Factors Adhesion- ability to adhere to mucus  membranes   2
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This note was uploaded on 11/18/2010 for the course BIOL 2051 taught by Professor Brininstool during the Spring '07 term at LSU.

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Bio2051ch25 - Chapter25 Chapter25MicrobialPathogenesis

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