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CHAPTER 15 MICROBIOLOGY

CHAPTER 15 MICROBIOLOGY - • PATHOGENITY the ability to...

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Unformatted text preview: • PATHOGENITY: the ability to cause disease • VIRULENCE: the extent of pathogenity • For a pathogen to cause disease it must: o Have access to host, adhere to host, colonize host, damage host • PORTALS OF ENTRY o Mucous membranes respiratory tract, gastrointestinal tract, urogenital tract, conjunctiva o Skin includes hair follicles and sweat gland ducts o Parenteral route deposited directly under skin – cuts, bites, injections, surgery **PREFERRED PORTAL OF ENTRY: many pathogens have a preferred portal of entry that is a prerequisite to their being able to cause disease **some organisms have MULTIPLE PORTS OF ENTRY • PORTALS OF EXIT o Respiratory tract- Coughing, sneezing o Gastrointestinal tract- Feces, saliva o Genitourinary tract o Urine, vaginal secretions o Skin o Blood- Biting arthropods, syringe needles ** Generally the same as the portal of entry for a given microbe • ID 50 : infectious dose for 50% of the test population; measures virulence o Examples: Skin: 10-50 endospores Inhalation: 10,000-20,000 endospores Ingestion: 250,000-1,000,000 endospores • LD 50 : lethal dose (of a toxin) for 50% of the test population o The lower the LD-50 number, the higher the potency ADHERENSE • How pathogens adhere to host o Almost all pathogens have some means of attaching themselves to host tissue @ portal of entry. o The Attachment between pathogen & host is accomplished by means of surface molecules on the pathogen called ADHESIONS or LIGANDS that bind specifically to complementary surface RECEPTORS on the cells of certain host tissue.RECEPTORS on the cells of certain host tissue....
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CHAPTER 15 MICROBIOLOGY - • PATHOGENITY the ability to...

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