MC3 - Chapter 5 and 6

• 5 kingdom classifications by Robert Whittaker

  • Animalia
  • Plantae
  • Protista
  • Fungi
  • Monera
• infectious disease process - the interaction between the pathogenic microorganism, the environment, and the host
• 6 links of infection process

  • infectious agent
  • reservoir
  • portal of exit
  • mode of transmission
  • portal of entry
  • susceptible host
• this is the person who is at risk for infection because they are unable to fight the infection

  susceptible host
• this is the microorganism (germ or bug) that can cause harmful infections and make you ill

  infectious agent
• this is where the germ lives and grows

  reservoir
• the germ then needs to find a way out of the infected person so it can spread

  portal of exit
• once the germ is out, it can spread from one person to another by hands or on equipment such as a commode, in the air by coughing or contact with body fluids and blood

  mode of transmission
• the germ then needs to find a way into another person

  portal of entry
• How well any pathogen can thrive depends on three factors:

  • Pathogenicity
  • Degree of virulence
  • Invasiveness
• pathogenicity - its ability to produce disease
• virulence - its severity or harmfulness
• invasiveness - its tendency to spread
• reservoir - a principal habitat in which a pathogen lives, flourishes, and can multiply
• 2 forms of reservoir in humans:

  • acute clinical cases
  • carriers
• 4 main types of carriers:

  • incubatory
  • inapparent
  • convalescent
  • chronic
• incubatory carriers - people who are infectious even before their own symptoms start
• inapparent carriers - in which an individual is able to transmit an infection to others, without ever developing the infection themselves
• convalescent carriers - people who are in the recovery phases of their illness but who continue to be infectious
• chronic carriers - anyone who has recovered but who continues to be a carrier for infection
• zoonosis - any infectious disease that is transmitted under natural conditions from animal to human
• key portals of exit:

  • alimentary
  • genitourinary
  • respiratory
  • skin
  • trans-placental
• 2 modes of transmission

  • direct
  • indirect
• direct transmission - occurs when there is direct contact with the infectious agent; examples include tetanus, glandular fever, respiratory diseases and sexually transmitted diseases
• indirect transmission - can occur through animate mechanisms such as fleas, ticks, flies, or mosquitoes or via inanimate mechanisms such as food, water, biological products or surgical instruments, can also be airborne
• inhalation - portal of entry via the respiratory tract
• absorption - portal of entry via mucous membranes such as the eyes
• ingestion - portal of entry via the gastrointestinal tract
• inoculation - portal of entry as the result of an inoculation injury
• introduction - portal of entry via the insertion of medical devices
• susceptible host - the last link in the chain of infection
• pathogenicity - the capability of a microorganism to cause a disease in a host; an innate property
• virulence - the quantity of pathogenicity of a microbe or a measure of the ability of the microbe to cause disease
• virulence is determined by the factors of invasiveness and toxigenicity
• To cause disease, pathogens must penetrate the host tissues and multiply. Usually, they become localized and form a small focus of infection. In some cases, secretion is produced, and is called PYOGENIC infection.
• bacteremia - non-multiplying bacteria in the blood stream
• septicemia - reproducing bacteria
• adhesins - are specific virulence factors that enhance the ability of a microorganism to attach to the surface of mammalian
• invasiveness - the ability of microorganisms to invade human tissues and to reproduce or multiply within the cells and tissues of the human body
• Iron is needed by the bacteria for their growth.