MICROBIO 310: EXAM 3
19 Cards in this Set
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• Define pathogens, pathogenicity, virulence, and opportunistic pathogen.
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-Pathogens: microbial parasites
Pathogenicity: ability to inflict damage to host
Opportunistic pathogen: causes disease only in the absence of normal host resistance
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• Where does microbial infection frequently begin?
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-At breaks or wounds in the skin or on the mucous membranes of the respiratory, digestive, or genitourinary tract.
-Bacteria or viruses able to initiate infection often adhere to epithelial cells through specific interactions between molecules on the pathogen and molecules on the host ce…
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• What is adherence?
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-The start site of a pathogen invasion.
-The pathogen may then spread throughout the host via the circulatory or lymphatic systems.
-Adherence is specific (host range).
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• What can bacterial adherence be facilitated by?
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-Extracellular macromolecules that are not covalently attached to the bacterial cell surface.
-Examples include: slime layers (loose network of polymers extending outward from a cell) and capsules (a polymer coat consisting of a dense, well-defined polymer layer surrounding the cell).
-…
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• What is colonization?
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-The phase after infection where a pathogen must multiply and colonize in the tissue.
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• What are important factors for colonization and infection?
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-The pathogen must find appropriate nutrients and environmental conditions in the host.
-The availability of microbial nutrients is most important, but temperature, pH, and the presence or absence of oxygen also affects pathogen growth.
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• What is invasion?
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-The ability of a pathogen to enter into host cells or tissues, spread, and cause disease.
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• What are virulence factors?
rmal host defense mechanisms.
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-A pathogen's means of indirectly or directly enhancing invasiveness by promoting pathogen colonization and growth.
-Many are in the form of enzymes
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• What enzymes are used by pathogens during invasion?
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-Enzymes that enhance virulence by breaking down or altering host tissue to provide access to nutrients.
-Enzymes that protect the pathogen by interfering with no
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• What are exotoxins?
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-Toxic proteins released from the pathogen cell as it grows.
-Exotoxins fall into 3 categories: cytolytic toxins, the AB toxins and the superantigen toxins.
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• Describe cytolytic toxins.
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-Work by degrading cytoplasmic membrane integrity, causing cell lysis and death.
-Toxins that lyse red blood cells are called hemolysins.
-Staphylococcal α-toxin kills nucleated cells and lyses erythrocytes.
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• Describe AB toxins.
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-Inhibit protein synthesis
-Examples include:
• diphtheria toxin
• tetanus toxin
• botulinum toxin
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• What are neurotoxins? What are some examples?
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-Toxins that affect nervous tissue.
-Clostridium tetani and Clostridium botulinum are two examples that produce potent AB exotoxins.
-Botulinum toxin consists of several related AB toxins that are the most potent biological toxins known; tetanus toxin is also an AB protein neurotoxin.
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• What are enterotoxins?
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-Exotoxins of the small intestine, causes vomiting and diarrhea.
-Example: cholera toxin.
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• What are endotoxins?
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-Toxic lipopolysaccharides that are part of the outer layer of most gram-negative Bacteria's cell envelope.
-This becomes a toxin when solubilized.
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• How do endotoxins differ from exotoxins?
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-Endotoxins are cell bound and released in larger amounts only when cells lyse, versus exotoxins, which are the secreted products of living cells.
-Endotoxins are generally less toxic than exotoxins.
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• How can the presence of endotoxins be detected?
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-By the Limulus amoebocyte lysate (LAL) assay.
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• What is the type III secretion system?
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-A translocase system for toxin excretion.
-The secreted protein is trans-located from the bacterial cell directly into the host cell.
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• Type III secretion from the slides:
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-Effectors
-Actin polymerization/entry
-Transcriptional activators/take over
-Induce apoptosis/exit
-Y pestis- plague, zoonotic (fleas)
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Microbio 310: Exam 1