Chapter 13

• True Pathogen


  Have the potential to cause disease in healthy people with normal immune defenses
• Opportunistic Pathogens


  Have the potential to cause disease when a person is immunocompromised or if microbes that are residents of one part of the body but move to another part of the body cause disease
• Opportunistic Pathogens


  • E. coli moving to the urinary tract and causing a UTI
• Virulence


  The ability for a microbe to establish itself in the host and for it to cause damage
• Portal of entry


  A way for microbes to enter the body and get to a place within the body that will cause disease
• Infectious Dose


  The concentration or number of microbes within a dose that will cause infection
• Colonization


  Microorganisms that are normally part of the microbiota for long periods and do not cause harm
• Infection


  Microbes get past the body's natural defenses and enter the body tissues and multiply. We may or may not be aware of the infection
• Disease


  The effects of the infection damage or disrupt the body's tissues and organs
• Virulent Factors


  • Toxins
  • Growth factors in the biofilm
  • Bind to host cell
  • Make changes and damage to the host cell
  • Excessive host response
  • Go deeper into host cell
  • Inhibit phagocytosis
• Endotoxins


  Composed of LPS which is shed by the outer membrane of gram-negative bacteria. Dead bacteria can be a threat if the outer membrane contains LPS
• Antibiotic treatment of endotoxins

  Bacteria does not need to be alive to release the endotoxin, it can be released during lysis as well
• Biofilms


  • Can cause chronic infections
  • Are resistant to antibiotics
  • Are resistant to host defenses
  • The protective film does not allow for the easy penetration of the antibiotics and the engulfment of phagocytes
  • Are composed of multiple microbes, if more than one is causing virulence then it is harder to treat because antibiotics cannot target all types of bacteria
• Endotoxins


  Secreted only by gram negative bacteria and both living and dead bacteria cells, causes systemic symptoms such as fever and inflammation, is composed of LPS, stable at 60 degrees, cannot be converted to a toxoid, and does not stimulate antitoxins
• Exotoxins


  Secreted by only living cells and both gram positive and negative bacteria, can be toxic within minutes, is specific to a cell type, is made of small proteins, is unstable at 60 degrees, can be converted to a toxoid, stimulates antitoxins, and does not induce a fever
• Ways microbes cause damage

  • Enzymes and toxins
  • Growth and multiplication
  • Cell lysis
  • Damage to the immune system
• Virulent factor examples are toxins, growth factors in the biofilm, bind to host cell, make changes and damage to the host cell,  excessive host response, go deeper into host cell, and inhibit phagocytosis. 
• Factors that influence if an individual will become infected is the microbes virulence, portal of entry and infectious dose. 
• Endotoxins are composed of LPS which is shed by the the outer membrane of gram-negative bacteria. Dead bacteria can be a threat if the outer membrane contains LPS. 
• Antibiotic treatment of endotoxin producing bacteria because the bacteria does not need to be alive to release the endotoxin, it can be released during lysis as well.