Microbiology - Chapter 14

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Microbiology - Chapter 14

• Non-Specific defenses to invasion and infection
• Lines of defense against infection or invasion
  both non-specific and
• specific

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Microbiology - Chapter 14

• Know for test

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Microbiology - Chapter 14

• 1st body systems that normally keeps microbes
  out of tissue and prevent
• disease
• a. intact skin
• 1. outer epidermis of dead epithelium cells,
  dry and unfavorable environment
• 2. keratin protein resist invasion
• 3. normal flora of skin microbes only a
  threat if skin is damaged (opportunists)

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Microbiology - Chapter 14

• b. mucous membranes and secretions
• 1. epithelium tissue lining the respiratory, GI
  tract, and genitourinary tract
• 2. have specialized goblet cells that secrete
  stick substance
• called mucous
• 3. respiratory tract have ciliated epithelial
  cells that move
• mucous up mucous traps microbes and particles,
  cilia move
• the material up - ciliary escalator-very
  efficient at protecting
• delicate tissues that are more easily invaded

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Microbiology - Chapter 14

• 4. sweat glands on skin produce perspiration that
  wash the skin
• 5. lysozyme in the sweat breaks down cell wall of
  gram
• positives
• 6. sebum in the skin is acidic-oily substance, pH
  of 3 to 5,
• inhibits growth of some microbes
• 7. stomach secretions, very acidic, kills most
  pathogens, some toxins are resistant

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Microbiology - Chapter 14

• c. normal microbial flora microbial antagonism,
  ecosystem on cellular level,
• 1. normal balance, keeps pathogens in check
• 2. if upset in balance, then microbe imbalance
  can result in problems yeast infections, or in
  broad spectrum antibiotics, organisms grow that
  usually wouldnt grow C.difficile, diarrhea

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Microbiology - Chapter 14

• Clostridium difficile is a bacterium that can be
  found in the colon. It can cause low-grade
  Diarrhea or severe colitis. It most commonly
  occurs when an individual is placed on
  antibiotics. The antibiotics kill off the good
  bacteria in the colon, and allow room for
  Clostridium difficile bacterium to grow. In
  addition, it can be contagiously spread from one
  person to another, especially in hospital and
  nursing homes

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Microbiology - Chapter 14

• 2nd line of defense, system elements,
  non-specific, go into action if 1st line is
• breached
• a. PHAGOCYTES VERY IMPORTANT, these cells
  engulf and destroy invaders and particulate
  matter
• 1. All of the phagocytes are types of white
  blood cells
• 2. circulating in the blood and found to some
  extent in tissue (modified forms), ready to
  respond to invasion
• 3. more later

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Microbiology - Chapter 14

• b. Inflammation and fever if tissue is damaged,
  inflammation reaction occurs and it is
  characterized by redness, pain, heat, swelling
• 1. non-specific response to tissue damage or
  invasion to limit and stop the infection or
  damage
• 2. many things cause an inflammation reaction
  infection, injury, even chemical action
• 3. purpose of inflammation reaction
• a. to destroy and remove the disease agent if
  possible
• b. limit the effect of the invading agent
• c. repair the damage at the site of injury

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Microbiology - Chapter 14

• 4. Several specialty proteins are involved at the
  injury site that aid in the processes that limit
  the invader and help destroy the invader, even
  help clean up and repair the damage
• complement, kinins, interferon, fibrin
• Blood cell formation illustrated on next slide

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Microbiology - Chapter 14

• 3rd line of defense - this is specific, a
  production of specific counteracting
• chemicals, called antibodies that can recognize
  and act on invaders to
• destroy them
• a. usually proteins
• b. produced by specialized lymphocytes (B and T
  cells)
• c. Cover in detail in chapter 15

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Microbiology - Chapter 14

• Process of Phagocytosis simplify into 4 stages
• 1. Chemotaxis phagocytes are chemically
  attracted to a site where invaders are present
• a. chemotactic mediators peptides from damaged
  tissues, microbial waste products, components
  from white blood cells
• b. these chemicals released at site of infection
  or injury attract the phagocytes (some in the
  tissue already, some circulating in the
  bloodstream)

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Microbiology - Chapter 14

• 2. Adherance attachment of phagocyte to invader
  or particle,
• a. opsonization some particles or agents are
  coated with serum proteins, thus allowing the
  phagocyte to more easily attach, some of the
• complement proteins act as opsonins
• b. some microbes produce capsules or proteins
  that
• resist phagocytic adherance, more virulent

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Microbiology - Chapter 14

• 3. Ingestion pseudopods of phagocytes surround
  invader or particle, once completely surrounded,
  the particle is said to be enclosed in a
  phagosome
• 4. Digestion a cellular organelle, a lysosome,
  fuses with the phagosome and the digestive
  enzymes of this new phagolysosome kill the
  microbe quickly (lipases, proteases, lysozyme,
  other digestive enzymes, plus strong oxidants and
  other radicles that can kill the microbe and
  break it down)
• a. the waste products are kept packaged
• b. the waste particles are expelled
• c. some microbes survive inside the phagocyte,
  get a free ride and phagocyte may actually help
  spread the agent to other tissues
• Shigella and Listeria, HIV virus, tubercle
  bacilli

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Microbiology - Chapter 14

• 5. Expulsion End products are expelled and
  filtered out and removed by other organ (liver)
• See next slide for diagram

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Process of phagocytosis
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Microbiology - Chapter 14

• Acute Inflammation Remember this is a
  non-specific reaction to the breach of the body
  primary defense barriers. The reaction is general
  and can be used to combat
• most all of the body invaders (bacteria, viruses,
  helminthes, protozoans)
• see slide to follow we will follow that diagram
• 1. injury or invasion, at site chemical signals
  are released
• 2. blood vessels dilate, opening up of diameter
  of blood vessel, increase blood flow,
• causing redness (erythema) and heat
• 3. Vasodilation and increased permeability of
  blood vessels are caused by chemicals
• released by damaged tissues

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Microbiology - Chapter 14

• i. histamine- found in mast cells of connective
  tissue, ad other tissue elements
• (a histamine reaction can be very serious in
  hypersensitivity reactions
• more later)
• ii. kinins several varieties, also increase
  permeability and vasodilation
• iii. prostaglandins are also released by damaged
  cells these chemicals allow more phagocytes to
  be attracted to the site and they in turn produce
  more chemicals that attract more phagocytes to
  the damaged area (mobilization of
• defenders) The movement into the damaged tissues
  of these cells is vital to stop the invaders at
  the local site.

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Microbiology - Chapter 14

• iv. Leukotrienes Chemicals produced by mast
  cells and basophils, they increase permeability
  of blood vessels (more phagocytes can leave blood
  to get into tissue that has the invader). They
  also help the phagocyte to attach to
• the invader cells.
• v. increased permeability allows blood elements
  that result in clot formation to exit into tissue
  to wall off area and prevent further invasion or
  tissue damage (fibrin net)
• vi. pus forms collection of dead cells and
  tissue fluid
• vii. localization of the site and walling off to
  prevent the spread of infection often produces an
  abscess (like a boil, or pustule) (remember what
  a fire ant bite looks like)

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Microbiology - Chapter 14

• 4. This acute inflammation activity, producing
  swelling , redness, pain, heat etc. limits and
  stops the invasion. The cells that migrate to the
  site then destroy the invaders
• and even begin the process of clean up repair.
  Ultimately healing of the site occurs.
• a. Mast cells (fixed tissue macrophages, contain
  histamine, very important in inflammation and
  repair of damaged tissue) are real involved in
  clean up and repair.

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Microbiology - Chapter 14

• b. Role of the group of chemicals called
  generally Complement.
• Complement is a series of proteins found
  circulating in blood plasma.
• These chemicals are inactive until needed and
  then activated to perform their role in helping
  prevent further invasion by microbes. Injury or
  infection triggers their activation. They then
  help trigger the bodys inflammation reaction.

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Microbiology - Chapter 14

• Complement
• 1. affect blood vessels permeability and
  dilation
• 2. actually attract leukocytes (phagocytes),
  activate phagocytes
• 3. produce inflammatory mediators
• 4. actually can act on microbes and cause them to
  lyse (rupture) cytolysis
• 5. the activation of complement is complicated
  and proceeds in a step wise
• process called a cascade see pg 441,
• 6. The complement cascade happens quickly and
  then is quickly shut off to prevent host cell
  damage.
• 7. Opsonization one complement cascade results
  in a fragment that attaches to invader cells and
  oposonizes them making them easier for
  phagocytes to attach to and thus destroy them

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Microbiology - Chapter 14
INTERFERONS non-specific antiviral proteins
produced by host cells when host is infected by a
virus 1. general not specific 2. 3 types -
alpha, beta, gamma 3. alpha and beta IF cause
uninfected cells to produce antiviral proteins
(inhibit some function of the virus mRNA
synthesis, or viral protein synthesis 4. gamma IF
can cause neutrophils to kill bacteria 5.
Recombinant DNA technology, production of
interferon by bacteria in pure form and in large
quantities to treat some diseases (herpes,
hepatitis B and C)
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INTERFERONS non-specific antiviral proteins
produced by host cells when host is infected by a
virus 1. general not specific 2. 3 types -
alpha, beta, gamma 3. alpha and beta IF cause
uninfected cells to produce antiviral proteins
(inhibit some function of the virus mRNA
synthesis, or viral protein synthesis 4. gamma IF
can cause neutrophils to kill bacteria 5.
Recombinant DNA technology, production of
interferon by bacteria in pure form and in large
quantities to treat some diseases (herpes,
hepatitis B and C)
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