Microbiology – Chapter 13 Pathology: Science of study of disease

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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

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. ***

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

Microbiology – Chapter 13

  • Parasitism: One benefits at the other’s 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)

Microbiology – Chapter 13

  • Pathogen: actual agent of disease, MRSA – S. aureus


  • 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)

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”)

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

Fig. 13.13

Review Koch’s postulates

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

Fig. 13.12

Microbiology – Chapter 13

  • 2. Fomites

  • Inanimate objects that spread disease agents

  • Shared drinking cups, baby toys in a nursery, contaminated sharps

  • ** add pictures**

Microbiology – Chapter 13

  • 3. Direct body contact- Oh what fun!!

  • Person to person:

  • STD,

  • Impetigo

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 disease;Helminth

  • Protozoans: Giardia, Balntidium

Microbiology – Chapter 13

  • 5. Arthropod Vectors

  • Flies, fleas, mosquito, tick

Fig. 13.11

Microbiology – Chapter 13

  • 6. Airborne

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

Microbiology – Chapter 13

  • 7. Parenteral

  • Direct transmission via blood: universal precautions


Microbiology – Chapter 13

  • 8. Deep Wound trauma

  • Gas gangrene and tetanus, even wound botulism

  • Beaman’s world infant tetanus

Microbiology – Chapter 13

  • 9. Horizontal: Mother to infant

  • Prenatal: across the placenta; HIV

  • Perinatal: at birth, STD like gonorrhea and syphilis, even Chlamydia blindness

Microbiology – Chapter 13

  • 9. Horizontal: Mother to infant

  • Perinatal: at birth, STD like gonorrhea and syphilis, even Chlamydia blindness

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

Fig. 13.4

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

Other Adhesions

  • SEM of Pseudomonas, Gram (-)

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.

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

Fig. 13.6

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.

Virulence Factors

  • Enzymes: Collagenase, Hyaluronidase

Virulence Factors

Microbiology – Chapter 13

  • Evading defenses – Once in tissue some organisms can “evade” the natural defense of a host.

    • Capsule – Phagocytes can’t 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)

Virulence Factors

  • Evade defenses: Capsule – resisting phagocytosis, Strep.

Virulence Factors

  • Adherence: Glycocalyx (capsule)

Virulence Factors

  • Surface proteins : Leukocydin, S. aureus

  • (MRSA) – Attacks WBC’S

M. tuberculosis inside lung macrophage

Virulence Factors

Evading immune response

  • Influenza

Virulence Factors

  • Evade immune response : Influenza A

  • H5N1 – “Bird Flu”

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)

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