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 Unit 12
   Tiny living organisms that we can not see
    but are everywhere
    –   On our skin
    –   In our mouths
    –   Within our bodies
    –   In and on food we eat
    –   On what we touch or handle
 Nonpathogens – do not produce disease,
  but help in many ways
 Pathogens – disease producers
 Grow   best in these conditions
  – Body temperature
  – Limited light
  – Where there is moisture
  – Where there is a food supply
  – Where oxygen needs are met
           – occur when pathogens
 Infections
 invade the body and cause disease
 Bacteria

 Viruses

 Fungi

 Protozoa
   Simple one-cell microbes
   Named according to shape and arrangement
   Cause infections in skin, respiratory tract, urinary
    tract, and bloodstream
   Shapes-
    – Coccus (cocci)- round or spherical
    – Bacillus (bacilli)- straight rod
    – Spirillum (spirilla) spiral, corkscrew, or slightly curved
   Arrangements –
    –   Single
    –   Pairs (diplo)
    –   Chains (strepo)
    –   Clusters (staphylo)
 Yeast   – single cell budding form of
  – Mouth/vagina- Candida albicans
  – Skin – Tinea capitis (ring worm)
  – Feet – Tinea pedis (athlete’s foot)
 Mold   –
  – Aspergillus infection in the lungs
 Parasites   –
  – Organisms that live in or on another
    living organism without benefitting the
   Smallest microbes has a variety of shapes
   Classified by
    – Type of nucleic acid (DNA or RNA)
    – Clinical properties
   Common types
    –   Hepatitis
    –   Herpes
    –   Acquired immune deficiency syndrome
    –   Chickenpox
    –   Influenza
    –   Common cold
    –   Measles
    –   Mumps
 Simple one-celled organism that live on
  living matter, true nucleus, classified by
  way move
 Diseases caused
    –   Malaria
    –   Toxoplasmosis
    –   African sleeping sickness
    –   Amebiasis
    –   S/S of parasitic infection
          Diarrhea
          Dysentery
          Encephalitis
         Chain of infection
 Conditions  that lead to infections
 Causative agent

 Reservoir or source

 Portal of exit

 Mode of transmission

 Portal of entry

 Susceptible host
 Where pathogen can survive
 Most common reservoirs
    –   Humans – active cases and carriers
    –   Animals
    –   Environment
    –   Fomites – contaminated objects
          Bedpans and urinals
          Doorknobs, faucet handles
          Linens
          Instruments
          Containers with specimens for laboratory analysis
          Human reservoirs
 Cases – people with acute illness including
  obvious S/S
 Carriers – those who have and transmit
  the disease organisms but have no
  symptoms, and do not display evidence of
  disease. Chronic and incubating.
  (indefinite period in humans- salmonella,
  hepatitis B, hepatitis C, HIV disease, and
         Portals of Entry or Exit
 Skin or mucous membranes
 Respiratory tract
 Genitourinary tract
 Gastrointestinal tract
 Circulatory system
 Transplacentral
 Excretions, draining wounds, urine,
  feces, blood, saliva, tears
       Transmission of disease
   Airborne –
    – small particles remain suspended in the air and
      move with air currents, or become trapped in
      dust. Pt breaths in the pathogen
   Droplet-
    – Moist particles produced by coughing,
      sneezing, talking, laughing, or sneezing.
      Transmitted into air, usually travel only three
      feet from source
   Contact
    – Direct or indirect contact with the source of the

 Does  not have enough resistance to
  the infectious agent
 Risk factors
  – Number and strength of infectious agent
  – General health of person
  – Age, sex, and heredity of individual
  – Condition of person’s immune system
  – Emotional stress and fatigue also play a
         Types of infection
 Localized(confined to one area)
 Generalized

 Systemic - widespread through the
               Body flora
 Disrupted   by
  – Pathogenic organisms
  – Normal flora become pathogenic
  – Flora from one area transferred to a
    different area
  – Drugs that upset normal conditions
      Ways produce disease
 Attack  and destroy cells
 Produce toxins

 Allergies
           Body defenses
 Mucous membranes
 Cilia
 Coughing and sneezing
 Hydrochloric acid of stomach
 Tears
 Fever
 Phagocytes
 Inflammation
 Immune response
    Immunity and immunizations
 Immunity- ability to fight off disease
  caused by microbes
 Antigen
 Antibodies
 Immunizations – artificial defense to
  protect against specific pathogens
 Vaccines – artificial or weakened antigens
  that help the body develop antibodies
  before need arises
 Available for most childhood diseases,
  pneumonia, influenza, hepatitis B
 Body’s immune system is inadequate and
  fails to respond to challenge of infectious
  disease organisms. More likely to develop
 Factors that can lead to
    –   Advanced age
    –   Frailty
    –   Drug therapy
    –   Infection with HIV
    –   Injury or removal of spleen
    –   Radiation therapy
             Bacterial infections
 Culture and sensitivity
 Methicillin resistant Staphylococcus aureus
 Vancomycin-resistant enterocci (VRE)
 Other bacterial
    –   Pseudomonas aeruginosa
    –   Escherichia coli
    –   Streptococcus A
    –   Salmonella
    –   Mycobacterium tuberculosis
 Antibiotic use in 1950s caused number of
  cases and deaths to drop
 Since 1985 number infected has increased
  along with increased in those at risk
    – HIV positive
    – Infected but fail to take treatment correctly
    – Live in poverty and malnourished
    – Immigrated to US from countries where TB still
    – Have inactive TB and have grown older and
      inexperience increased disability
             TB continued
 TB infection occurs when bacterium enters
  the body, body develops protective barrier
  called a tubercle to keep infection from
  rest of body. Person is not contagious
 TB disease- tubercle breaks down or more
  tuberculosis bacteria enter body. Multiply,
  tissue damage increases, bacteria spreads
  to other parts of body
 S/S- fatigue, loss of appetite and weight,
  weakness, elevated temperature in
  afternoon and evening, night sweats,
  hemoptysis, coughing
                TB continued
   Diagnosis
    – Sputum culture
    – Chest x-rays
    – Positive skin test (Mantoux test)
   Treatment
    – Selected antibiotic or combination of antibiotics
    – Becomes noncontagious within two to three
    – Treatment continues six months to two years
         Escherichia coli 0157:H7
   Found in intestines of some cattle. Contaminate
    meat especially ground beef.
   Best way to prevent spread good handwashing
    and food preparation practices
   S/S watery diarrhea, nausea, vomiting, and
    cramping. 2 days bloody diarrhea, abdomen
    distended and very tender. Dehydration,
    swelling, petechiae. Damage to mucous
    membranes allows bacteria to enter bloodstream
   Leads to renal problems possible failure, mental
    confusion, seizures, muscle weakness, pain and
    numbness in feet and legs
          E. Coli continued
 Tx-
  – Contact isolation until diagnosis.
    Diapered or incontinent persons in
    contact for duration of illness. Standard
    precautions for others
  – Care is supportive with careful
    monitoring. Many drugs increase risk of
    kidney damage. Fluid intake carefully
    monitored. Vital signs carefully
   Pseudomembranous Colitis
 Serious condition in which diarrhea is
  caused by Clostridium difficile(C Diff)
 Pt has been on antibiotics. C difficile
  breeds rapidly produces toxins
 Common in health care facilities
 s/s can occur weeks or months
  following antibiotic treatment. Toxin
  causes inflammation of bowel which
  produces sudden, severe, foul-
  smelling, watery diarrhea
     Diagnosis and treatment
 Stool cultures
 Stop antibiotic if possible, treat with
 Yogurt to eat and other medications
  to increase balance of bacteria in
 Contact precautions until 72 hours
  after stools return to normal

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