Understanding the Principles of

							Understanding the Principles of
Infection Control
(How Disease is Transmitted and What Are the Main
Ways to Prevent It)
Microorganism (aka Microbe)
   Small living plant or animal
    ◦ Not visible to the naked eye
    ◦ Must be viewed under a microscope
 Found everywhere in the environment,
  including on and in the human body
 Many microbes are part of normal flora of
  the body
    ◦ Beneficial in maintaining certain body
      processes
    ◦ Called nonpathogens
Microorganism (aka Microbe)
   Other microbes cause infection and
    disease
    ◦ Called pathogens or germs
   At times, a microbe that is beneficial in
    one body system can become pathogenic
    in another body system
    ◦ Bacteria called Escherichia coli (E. coli) is part
      of the natural flora of the large intestine
    ◦ If E. coli enters the urinary system it causes an
      infection (UTI)
Classifications of Microbes
 Bacteria
 Protozoa
 Fungi
 Rickettsiae
 Viruses
Bacteria
 Simple one-celled plants that multiply
  rapidly
 Classified by shape and arrangement (pg
  269)
    ◦ Cocci
    ◦ Bacilli
    ◦ Spirilla
Bacteria - Cocci
 Round or spherical in shape
 Diplococci
    ◦ Cocci that occur in pairs
    ◦ Cause diseases such as gonorrhea, meningitis,
      and pneumonia
   Streptococci
    ◦ Cocci that occur in chains
    ◦ Causes diseases such as strept throat and
      rheumatic fever
Bacteria - Cocci
   Staphylococci
    ◦ Cocci occur in clusters or groups
    ◦ Most common pyogenic microbe (pus
      producing)
    ◦ Causes infections such as boils, wound
      infections, and toxic shock
Bacteria - Bacilli
 Bacteria that are rod-shaped
 Can occur singly, in pairs, or in chains
 Many bacilli contain flagella that allow the
  organism to move
 Bacilli have ability to form spores or thick
  walled capsules when growing conditions
  are poor. Spores are extremely difficult to
  kill
 Causes diseases such as tuberculosis,
  tetanus, botulism, and pertussis
Bacteria - Spirilla
 Bacteria that are spiral in shape
 Also included the comma-shape (vibrio)
  and corkscrew shaped (spirochete)
 Causes diseases such as syphilis and
  cholera
Protozoa
 One-celled animals
 Often found in decayed materials and
  contaminated water
 Some protozoa are pathogenic and cause
  diseases such as malaria, amebic
  dysentery, trichomonas, and African
  sleeping sickness
Fungi
 Simple plantlike organisms
 Live on dead organic matter
 Yeasts and molds are two common forms
  of fungi that can be pathogenic
 Often found in decayed materials and
  contaminated water
 Causes diseases such as ringworm,
  athlete’s foot, histoplasmosis, yeast
  vaginitis, and thrush
Rickettsiae
   Parasatic microorganisms
    ◦ Cannot live outside the cells of another living
      organism
    ◦ Commonly found on fleas, lice, ticks, and mites
    ◦ Transmitted to humans by the bites of these
      insects
   Causes diseases such as Lyme Disease
    and Rocky Mountain spotted fever
Viruses
 Smallest microbe – visible only in an
  electron microscope
 Cannot reproduce unless they are inside
  another living cell
 Spread from human to human by blood
  and body secretions
 Very difficult to kills b/c resistant to many
  disinfectants and usually not affected by
  antibiotics
Viruses
 Causes diseases such as common cold,
  measles, chickenpox, herpes, warts, and flu
 Also causes the two diseases that are of
  major concern to health care workers
    ◦ Hepatitis B
    ◦ Acquired Immune Deficiency Syndrome
      (AIDS)
Hepatitis B
 Caused by the HBV
 Transmitted by blood and body secretions
 Affects the liver and can lead to
  destruction and scarring of liver cells
 Vaccine consisting of a series of 3
  injections has been developed to protect
  individuals
Hepatitis B
 Under federal law, employers must
  provide the vaccination at no cost to any
  health care worker with occupational
  exposure to blood or other body
  secretions
 Individual does have the right to refuse
  the vaccination, but a written record must
  be kept proving that the vaccine was
  offered
AIDS
 Caused by the HIV (Human
  Immunodeficiency Virus)
 Suppresses the immune system
 Individuals cannot fight off many cancers
  and infections that would not affect a
  health person
 No cure or vaccine
 Important to take precautions to prevent
  the spread of this disease
Factors Required for Microbe
Growth
   Microbes need certain things to grow and
    reproduce
    ◦ Most microbes prefer warm (body temp is
      perfect)
    ◦ Most microbes prefer darkness as many are killed
      quickly by sunlight
    ◦ Source of food and moisture is needed
    ◦ Need for oxygen varies
      Aerobic organisms require oxygen to live
      Anaerobic organisms live and reproduce in the absence
       of oxygen
   Human body is ideal supplier of all of the
    requirements
How Pathogens Cause Infection and
Disease
   Some pathogens produce poisons (toxins)
    which harm the body
    ◦ Ex. Bacillus tetanus – produces toxins that
      damage central nervous system
   Some pathogens cause an allergic reaction
    resulting in a runny noise, watery eyes, and
    sneezing
   Some pathogens attack and destroy the
    living cells that they invade
    ◦ Ex. Protozoa that causes malaria – invades red
      blood cells and causes them to rupture
Classifications of Diseases and
Infections
 Endogenous
 Exogenous
 Nosocomial
 Opportunistic
Endogenous Diseases and Infections
 Means the infection or disease originates
  within the body
 Includes metabolic disorders, congenital
  abnormalities, tumors, and infections
  caused by microbes within the body
Exogenous Diseases and Infections
 Means the infection or disease originates
  outside the body
 Includes pathogenic organisms that invade
  the body, radiation, chemical agents,
  trauma, electric shock, and temperature
  extremes
Nosocomial Diseases and Infections
 Infections acquired by an individual in a
  health care facility
 Usually present in facility and transmitted
  by health care workers to the patient
 Many of the pathogens transmitted in this
  manner are antibiotic-resistant and can
  cause life-threatening infections
 Includes methicillin-reisistant
  Staphylococcus aureus (MRSA) and
  Clostridium difficile (C. diff)
Opportunistic Diseases and
Infections
 Infections that occur when the body
  defenses are weak
 Diseases do not usually occur in
  individuals with an intact immune system
 Includes Kaposi’s sarcoma and
  Pneumocystis carinii pneumonia in
  patients with AIDS
Chain of Infection
   6 factors that must exist for disease to
    occur and spread from one person to
    another
    ◦   Causative agent
    ◦   Reservoir
    ◦   Portal of exit
    ◦   Means of transmission
    ◦   Portal of entry
    ◦   Susceptible host
Chain of Infection – Causative Agent
   Pathogen such as a bacteria or virus
Chain of Infection – Reservoir
 Place where causative agent can live
 Common reservoirs include human body,
  animals, environment, fomites, or objects
  contaminated with infectious material
  that contains pathogens (ex. Bedpans,
  urinals, linens, instruments, and specimen
  containers)
Chain of Infection – Portal of Exit
 Way for causative agent to escape from
  the reservoir
 Pathogens can leave the body through
  urine, feces, saliva, blood, tears, mucous
  discharge, sexual secretions, and draining
  wounds
Chain of Infection – Mode of
Transmission
 Pathogen must be transmitted to another
  reservoir or host where it can live
 Can be transmitted in 2 different ways
    ◦ Direct contact
    ◦ Indirect contact
Chain of Infection – Mode of
Transmission
   Direct contact
    ◦ Person-to-person, spread by physical or
      sexual contact
    ◦ Contact with a body secretion containing
      pathogen
    ◦ Contaminated hands are one of the most
      common sources of direct transmission
Chain of Infection – Mode of
Transmission
   Indirect contact
    ◦ Pathogen is transmitted from contaminated
      substances such as food, air, soil, insects, feces,
      clothing, instruments and equipment
    ◦ Touching contaminated equipment and
      spreading the pathogens on the hands
    ◦ Breathing in droplets carrying airborne
      infections
    ◦ Receiving the bite of an insect carrying a
      pathogen
Chain of Infection – Portal of
Entry
 Way to enter a new reservoir or host
 Different portals of entry
    ◦   Breaks in the skin or mucous membrane
    ◦   Respiratory tract
    ◦   Digestive tract
    ◦   Genitourinary tract
    ◦   Circulatory system
Chain of Infection – Susceptible
Host
 Individual who can contract the disease
 Usually humans can fight off causative
  agent and not contract a disease due to
  body defenses
 Human becomes susceptible host in some
  instances
    ◦ Large numbers of the pathogen invade the
      body
    ◦ Body defenses are weak
Chain of Infection – Susceptible
Host
   Common body defenses
    ◦ Mucous membrane that lines the respiratory,
      digestive, and reproductive tract and traps pathogens
    ◦ Cilia lining the respiratory tract to propel pathogens
      out of the body
    ◦ Coughing and sneezing
    ◦ Hydrochloric acid in the stomach to destroy
      pathogens
    ◦ Tears in the eye that contain bactericidal chemicals
    ◦ Fever
    ◦ Inflammation resulting in leukocytes or white blood
      cells destroying pathogens
    ◦ Immune response where the body produces
      antibodies (protective proteins that combat
      pathogens)
Ending the Chain of Infection
 If any part of the chain can be eliminated, the
  spread of disease of infection will be stopped
 Follow practices to interrupt or break this
  chain
 Prevent transmission of disease
 Important to remember that pathogens are
  everywhere
 Preventing pathogen transmission is a
  continuous process
 See page 272 for ways to break the chain
Aseptic Techniques
   A major way to break the chain of
    infection
    ◦ Asepsis: absence of disease-producing
      microorganisms or pathogens
    ◦ Contaminated: any object or area that may
      contain pathogens
   Aseptic techniques are directed toward
    maintaining cleanliness and eliminating or
    preventing contamination
Common Aseptic Techniques
 Handwashing and good personal hygiene
 Using disposable gloves when contacting
  body secretions or contaminated objects
 Proper cleaning of instruments and
  equipment
 Thorough cleaning of the environment
Levels of Aseptic Control
 Antisepsis
 Disinfection
 Sterilization
Antisepsis
 Antiseptics prevent or inhibit the growth
  of pathogenic organisms
 Usually not effective against spores and
  viruses
 Can usually be used on the skin
 Examples: alcohol and Betadine
Disinfection
 Process that destroys or kills pathogenic
  organisms
 Not always effective against spores and
  viruses
 Chemical disinfectants can irritate or
  damage the skin and are mainly used on
  objects.
 Examples: bleach and aldehydes
Sterilization
 Process that destroys ALL
  microorganisms – pathogenic and
  nonpathogenic, including spores and
  viruses
 Examples: steam under pressure, gas,
  radiation, and certain chemicals
 Autoclave is the most common
  equipment used