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Copyright © 2010 Pearson Education, Inc. MICROBIAL MECHANISMS OF PATHOGENICITY Chapter 15
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Copyright © 2010 Pearson Education, Inc. Mechanisms of Pathogenicity Pathogenicity: The ability to cause disease Virulence: The extent of pathogenicity, the amount of “damage” done
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Copyright © 2010 Pearson Education, Inc. Portals of Entry Mucous membranes- nose/ mouth/ lungs/ intestines Skin Parenteral route- injection/ IV/ wound Preferred portal of entry
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Copyright © 2010 Pearson Education, Inc. Portals of Entry Streptococcus pneumoniae if inhaled can cause pneumonia if enters the G.I. Tract, no disease Salmonella typhi if enters the G.I. Tract can cause Typhoid Fever if on skin, no disease
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Copyright © 2010 Pearson Education, Inc. Portal of EntryID 50 Skin10–50 endospores Inhalation10,000–20,000 endospores Ingestion250,000–1,000,000 endospores Bacillus anthracis
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Copyright © 2010 Pearson Education, Inc. Portal of EntryID 50 Botulinum0.03 ng/kg Shiga toxin250 ng/kg Staphylococcal enterotoxin1350 ng/kg Toxins Shiga:1/160 th of human hair
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Copyright © 2010 Pearson Education, Inc. Adherence Adhesins/ligands bind to receptors on host cells Glycocalyx: Streptococcus mutans Fimbriae: Escherichia coli M protein: Streptococcus pyogenes Form biofilms
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Copyright © 2010 Pearson Education, Inc. Adherence Figure 15.1
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Copyright © 2010 Pearson Education, Inc. Adherence Figure 15.1
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Copyright © 2010 Pearson Education, Inc. Adherence Figure 15.1
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Copyright © 2010 Pearson Education, Inc. Capsules Prevent phagocytosis Streptococcus pneumoniae Haemophilus influenzae Bacillus anthracis
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Copyright © 2010 Pearson Education, Inc. Cell Wall Components M protein resists phagocytosis Streptococcus pyogenes Opa protein inhibits T helper cells Neisseria gonorrhoeae Mycolic acid (waxy lipid) resists digestion Mycobacterium tuberculosis
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Copyright © 2010 Pearson Education, Inc. Enzymes Coagulase: Coagulates fibrinogen Kinases: Digest fibrin clots Hyaluronidase: Hydrolyzes hyaluronic acid Collagenase: Hydrolyzes collagen IgA proteases: Destroy IgA antibodies
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Copyright © 2010 Pearson Education, Inc. Membrane Ruffling Figure 15.2
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Copyright © 2010 Pearson Education, Inc. Antigenic Variation Alter surface proteins Figure 22.16
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Copyright © 2010 Pearson Education, Inc. Invasins Salmonella alters host actin to enter a host cell Use actin to move from one cell to the next Listeria Penetration into the Host Cell Cytoskeleton Figure 15.2 Salmonella
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Copyright © 2010 Pearson Education, Inc. Direct Damage Disrupt host cell function Produce waste products Toxins
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Copyright © 2010 Pearson Education, Inc. The Production of Toxins Toxin: Substance that contributes to pathogenicity Toxigenicity: Ability to produce a toxin Toxemia: Presence of toxin in the host's blood Toxoid: Inactivated toxin used in a vaccine Antitoxin: Antibodies against a specific toxin
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Copyright © 2010 Pearson Education, Inc. Figure 15.4 Exotoxins and Endotoxins
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Copyright © 2010 Pearson Education, Inc. Exotoxins Specific for a structure or function in host cell Figure 15.4a
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Copyright © 2010 Pearson Education, Inc. Membrane-Disrupting Toxins Lyse host’s cells by Making protein channels in the plasma membrane –Leukocidins –Hemolysins –Streptolysins Disrupting phospholipid bilayer
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Copyright © 2010 Pearson Education, Inc. Superantigens Cause an intense immune response due to release of cytokines from host cells Symptoms: fever, nausea, vomiting, diarrhea, shock, and death
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Copyright © 2010 Pearson Education, Inc. Endotoxins and the Pyrogenic Response Figure 15.6
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Copyright © 2010 Pearson Education, Inc. LAL Assay Limulus amoebocyte lysate assay Amoebocyte lysis produces a clot Endotoxin causes lysis
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Copyright © 2010 Pearson Education, Inc. Pathogenic Properties of Fungi Fungal waste products may cause symptoms Chronic infections provoke an allergic response Tichothecene toxins inhibit protein synthesis Fusarium Proteases Candida, Trichophyton Capsule prevents phagocytosis Cryptococcus
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Copyright © 2010 Pearson Education, Inc. Pathogenic Properties of Fungi Ergot toxin Claviceps Aflatoxin Aspergillus Mycotoxins Neurotoxins: Phalloidin, amanitin Amanita
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Copyright © 2010 Pearson Education, Inc. Pathogenic Properties of Protozoa Presence of protozoa Protozoan waste products may cause symptoms Avoid host defenses by Growing in phagocytes Antigenic variation
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Copyright © 2010 Pearson Education, Inc. Pathogenic Properties of Helminths Use host tissue Presence of parasite interferes with host function Parasite's metabolic waste can cause symptoms
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Copyright © 2010 Pearson Education, Inc. Pathogenic Properties of Algae Paralytic shellfish poisoning Dinoflagellates Saxitoxin Figure 27.13
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Copyright © 2010 Pearson Education, Inc. Portals of Exit Respiratory tract Coughing and sneezing Gastrointestinal tract Feces and saliva Genitourinary tract Urine and vaginal secretions Skin Blood Biting arthropods and needles or syringes
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Copyright © 2010 Pearson Education, Inc. Mechanisms of Pathogenicity Figure 15.9
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