Microbiology

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Microbiology Chapter 13

• Pathology Science of study of disease
• Etiology Cause of disease often microbial
• Flu etiological agent, Influenza virus
• Tb M. tuberculosis
• Pathogenesis development of disease in the host
  - Norwalk virus Fecal oral, diarrhea
• Disease altered state of health, host body is
  changed, upset of homeostasis

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Microbiology Chapter 13

• Epidemiology Science of the study of how
  diseases are acquired and spread in a population
• Outside assignment 3 Note that the last
  question has been changed to focus on MDR
  bacterial infections. Be sure to get a copy of
  the last page from instructor
• You may have to do some research ato answer
  all of the questions. Use other Micro. Books or
  other research tools.

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Microbiology Chapter 13

• Relationship between organisms
• Normal flora normal inhabitants of the host
• ex. S.epidermidis on skin, E.coli in intestine
• Commensalism One organism benefits the other
  unaffected can be opportunistic infector
• Mutualism both benefit E. coli makes us Vit.
  K We provide nice environment and food

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Microbiology Chapter 13

• Parasitism One benefits at the others expense
  tapeworm or leach
• Virulence potency how quickly they infect,
  spread, cause tissue damage or disease symptoms
  Influenza A H5N1, very virulent form of flu, or
  encapsulated pneumococci
• Virulence factors factors that cause disease or
  aid in spread of disease quickly in host or to
  other hosts (more later)

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Microbiology Chapter 13

• Pathogen actual agent of disease, MRSA S.
  aureus
• BACTERIAL, VIRAL, FUNGAL, HELMINTH
• Carrier Infected healthy individual, no
  symptoms (asymptomatic), or very mild form of
  disease, yet they both can spread disease to
  others many bacterial and viral pathogens
• Classic case was typhoid Mary (look it up)

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Microbiology Chapter 13

• Reservoir Where pathogen is maintained , can be
  in an organism (animal), in the environment
  (stagnant water - Legionella), or even in soil
  (Clostridia)
• Vector Agent that spreads pathogens from host
  to host
• 1. Arthropod flea mosquito, tick
• 2. Inanimate things, toys, dirty hands,
  needles, (sometimes called fomites)

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Microbiology Chapter 13

• Nosocomial infections hospital acquired
  infections see table in text and know it
• Next slide
• MRSA both HA and CA
• Pseudomonas - respiratory impaired, burn
  patients
• E. coli and Proteus UTI long term catheter
  patients

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Fig. 13.13
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Review Kochs postulates
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Microbiology Chapter 13

• Nine routes of infection
• Know this be able to list and give an
  example of each
• 1. Respiratory droplets cough sneeze, air born
  droplets
• Flu, colds, Strep throat even Staph infections
  of wounds

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Fig. 13.12
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Microbiology Chapter 13

• 2. Fomites
• Inanimate objects that spread disease agents
• Shared drinking cups, baby toys in a nursery,
  contaminated sharps
• add pictures

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Microbiology Chapter 13

• 3. Direct body contact- Oh what fun!!
• Person to person
• STD,
• Impetigo

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Microbiology Chapter 13

• 4. Fecal Oral
• Feces contamination of food water, even dirty
  hands (hands are a vector, or even a house fly or
  roach)
• Enteric diarrheal diseaseHelminth
• Protozoans Giardia, Balntidium

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Microbiology Chapter 13

• 5. Arthropod Vectors
• Flies, fleas, mosquito, tick

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Fig. 13.11
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Microbiology Chapter 13

• 6. Airborne
• Particles suspended in air (dry dust), travel
  long distances tb, anthrax spores (potential for
  WMD), Respiratory fungal infections (Histoplasma)

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Microbiology Chapter 13

• 7. Parenteral
• Direct transmission via blood universal
  precautions
• HIV, HVB, HVC

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Microbiology Chapter 13

• 8. Deep Wound trauma
• Gas gangrene and tetanus, even wound botulism
• Beamans world infant tetanus

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Microbiology Chapter 13

• 9. Horizontal Mother to infant
• Prenatal across the placenta HIV
• Perinatal at birth, STD like gonorrhea and
  syphilis, even Chlamydia blindness

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Microbiology Chapter 13

• 9. Horizontal Mother to infant
• Perinatal at birth, STD like gonorrhea and
  syphilis, even Chlamydia blindness

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Microbiology Chapter 13

• Virulence factors
• Virulence factors factors that aid or enhances
  the microbes ability to invade and spread within
  the host (know for test) Ex. List the
  categories of virulence factors in microbes
  explain each category, and give an example of a
  disease causing agent for each category.
• Adherence In order for a microbe to cause
  disease it first must adhere to a host surface.
  Some microbes produce materials or structures
  that allow them to adhere (stick) to membranes
  or surfaces, and thus escape defenses
• Pili (fimbriae) Neisseria gonorrhea, if a
  strain has no pili it is not pathogenic. The
  chemicals that allow such attachment are called
  adhesins They are often glycoproteins or
  protein that bind to receptors on host cell
  surfaces.
• Glycocalyx The capsule again is a tightly
  bound polyscaccharide material on the outside of
  certain bacterial cells (part of a bacterial
  envelope). Streptococcus pneumoniae is good
  example. Virulent strains are encapsulated
  non-virulent strains are not. Recall the
  classic Griffith experiment from chapter 9?
  Transformation?
• Spikes Viral envelopes of some viruses,
  Influenza a, H5N1

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Fig. 13.4
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Microbiology Chapter 13

• Other adhesions
• N. menigitidis (bacterial meningitis agent)
  produces protein a, a surface adhesion on the
  pili
• Mycoplasma pneumonia (atypical bacterial
  pneumonia) has a surface adhesion that binds to
  receptor on mucus membrane lining of the
  respiratory tract

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Other Adhesions
Virulence Factors

• SEM of Pseudomonas, Gram (-)

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Microbiology Chapter 13

• Toxins Poisonous microbial bypoducts that are
  produced by the microbe and diffuse into tissues
  causing damage/ enhance invasion/ avoid defenses
• Exotoxins excreted outside of cell, both Gram
  and Gram bacteria produce some of these highly
  destructive proteins.
• Staphylococcus aureus - Staph exotoxin that
  causes FBI
• Another causes SSSS Staph Scalded Skin
  Syndrome (exfoliate)
• C. botulinum most powerful neurotoxin, - a
  taste can kill you
• Streptococcus pyogenes - has several tissue
  destroying toxins Necrotoxin of flesh eating
  Strep would be a good example.
• Endotoxin Released by many Gram (-) bacteria
  when cells lyse, Examples
• Lipid A, lps in many pathogenic enteric
  bacteria like Shigella, can cause high fevers
  and even shock.

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• Endotoxin - Lipid A raises fever, and shock in
  Gram (-) pathogens

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Endotoxin - Lipid A raises fever, and shock in
Gram (-) pathogens
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Fig. 13.6
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Microbiology Chapter 13

• Enzymes that help invasion
• Collagenase breaks down collagen, the protein
  holding cells together, thus allows spreading.
  Clostridia that invade tissue can produce these
  proteases to digest connective tissue elements
  (C. perfringens)
• Hyaluronidase breaks down hyaluronic acid, the
  polysachharide that may hold some cells together,
  S. pyogenes produces such an enzyme
• Causes necrosis and blackening of tissue (inches
  of progression in hours)
• Coagulase Affects the fibrin in blood causing
  it to clot, Staph aureus produces one and maybe
  prevents phagocytosis.
• Hemolysin This exotoxin is an enzyme and lyses
  RBC. S. pyogenes
• Alpha and Beta Hemolysis of the Strep.

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Virulence Factors

• Enzymes Collagenase, Hyaluronidase

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Virulence Factors

• Enzymes Hemolysin lyse RBC

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Microbiology Chapter 13

• Evading defenses Once in tissue some organisms
  can evade the natural defense of a host.
• Capsule Phagocytes cant engulf the pathogen
  S. pneumoniae
• Surface proteins Proteins prevent phagocytosis
  (leukostatin, leukocydins of Staph and Strep)
• Survive inside phagocyte Get a free ride and
  spread (Tubercle bacillus, Listeria bacillus, and
  others)
• Evade immune response - Genetic variability
  occurs and the result is that antibodies lose
  effectiveness quickly genetic shift/drift of
  the antigenic nature of the Influenza A virus,
  (FDA today is meeting to SWAG for next years
  vaccine)

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Virulence Factors

• Evade defenses Capsule resisting
  phagocytosis, Strep.

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Virulence Factors

• Adherence Glycocalyx (capsule)

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Virulence Factors

• Surface proteins Leukocydin, S. aureus
• (MRSA) Attacks WBCS

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M. tuberculosis inside lung macrophage
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Virulence Factors

• Survive inside phagocyte, tubercle bacillus

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Evading immune response

• Influenza

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Virulence Factors

• Evade immune response Influenza A
• H5N1 Bird Flu

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Microbiology Chapter 13

• Iron binding Iron is tightly bound in our
  bodies and microbes need it to grow,
• Those organisms that can acquire it have and
  advantage and can spread faster
• more virulent Cholera is an example, HIB (H.
  influenza B)