Chapter 18

• What are the five required steps for a pathogen to cause disease in its host (pathogenesis)?


  1.) Entry into host

  2.) Attachment and colonization

  3.) Avoidance of host immunity

  4.) Host damage

  5.) Exit from host
• What are virulence factors?


  Factors that contribute to the ability of a pathogen to cause disease.
• What happens when horizontal gene transfer transfers virulence factors?


  It enables bacteria to enter and survive in a host
• What is a genomic island?

  Genomic island: a distinct region in a genome that has been acquired through horizontal gene transfer.
• What is a pathogenicity island?

  Genomic region but if it increases the fitness of a microbe
• What is the Griffith Experiment?


  Experiment in 1928 that found that mice injected with dead virulent pneumococcus were killed and transformation occured
• How did transformation occur in the Griffith experiment?


  DNA from dead cells transformed the living cells
• What are adhesins?


  Any microbial factor that promotes attachment
• What does the protein pilin do?


  Assembles into adhesion molecules called pili or fimbriae
• How does pili mechanism work?


  The tip of the pili is assembled first at the cell surface and is the adhesin protein that binds to its host receptors
• How is the tip of the pili pushed further from the surface?


  Pilin protein subunits are assembled at the cell surface to form a cylindrical structure
• What is the difference between Type 1 Pili and Type 4 Pili?


  Adhesion vs. twitching motility and adhesion
• What are biofilms?

  Aggregations of microorganisms that form a protective matrix on surfaces.
• Pathogens must acquire what when attatched?

  Nutrients and growth
• What is quorum sensing?


  Cell-cell communication
• How do biofilms lead to chronic infections?

  Bacteria in biofilm infections resist host defenses and antimicrobial compounds
• How does chronic inflammation work when biofilms are present?


  It activates toll-like receptors and triggers inflammation
• How does biofilms develop?

  Pili-mediated adhesion to the host triggers biofilm development
• What are the steps in bacterial pathogenesis? (*extracellular bacteria)


  1.) entry into body

  2.) adhesion to host surface or tissue

  3.) colonization

  4.) biofilm development
• What are the steps in intracellular bacterial pathogenesis?


  1.) adhesion to host surface or tissue

  2.) entry into cells

  3.) colonization

  4.) biofilm development
• How do pathogens know when virulence genes should be expressed?


  They use environmental clues
• How do pathogens sense they are in our bodies?

  They sense environmental conditions like temp and pH
• What are capsules?


  They coat bacterial walls that masked PAMPs and antigens, and prevent phagocytes from binding
• What do cell surface proteins do?

  Cell surface proteins like protein A can make antibodies by binding the Fc region and secrete fake cytokines
• How do pathogens manipulate host immune cells?

  By producing cytokines or using quorum sensing to induce virulence factor gene expression
• What can avoid innate and humoral immune mechanisms by living inside host cells?

  Intracellular pathogens
• What do facultative intracellular pathogens do?

  They can invade host cells but also survive outside the host cell
• What are obligate intracellular pathogens?

  They invade and reproduce inside a host cell
• What is fate 1?

  Can survive and replicate within phagolysosomes
• What is fate 2?

  Can prevent lysosome fusion and persist in phagosome by using exocytosis to expel bacteria into extracellular space or using phagocytes to ingest pathogens and deliver them to lymph nodes
• What is fate 3?

  Can break out of phagosome and move throughout cytoplasm and adjacent cells
• What is endotoxin?


  AKA lipopolysaccharide, is an important virulence factor common to all Gram-negative bacteria
• What is endotoxin composed of?


  Lipid A
• What does an endotoxin do?


  It activates troll-like receptors to cause a cytokine storm, contributing to signs and symptoms of sepsis
• What are exotoxins?


  Toxins released or secreted by bacteria.
• How are exotoxins transported out of the cell?


  Using secretion systems
• Both Gram-positive and Gram-negative use what to move many proteins across the cytoplasmic membrane?

  General secretion pathway
• What can use specialized type II, III, IV secretion systems to export what?

  Gram-negative rods to export exotoxins out of the cell
• How do Gram-positive cells use the GSP? (Type II SS)


  It transports proteins outside the cell and into the periplasm for Gram-negative cells
• How do Gram-negative cells use the GSP? (Type II S)

  It acts as the piston that uses ATP to push proteins outside of the cell