CALS Farm and Industry Short Course Program: Farm Microbiology: Lecture Outlines

SECTION 6.
Microbial Diseases of Humans, Animals and Plants

PART ONE – BACKGROUND

  1. Concepts of host-parasite relationships.

    1. Parasite.

    2. Host.

    3. Infectious disease.

    4. Pathogenicity.

    5. Virulence.

    6. Contagious disease.

    7. Epidemic.

    8. Endemic.

    9. Host's natural resistance.

    10. Host immunity.

  2. Koch and his Postulates:

    1. Who was Koch?

    2. Koch's Postulates

      1. Infection.

      2. Isolation.

      3. Re-infection.

      4. Re-isolation.

  3. Pathogenic mechanisms of bacteria.

    1. Invasive qualities.

      1. Easy portals of entry for any potential pathogen.

      2. Colonization.

      3. Spreading factors.

      4. Resistance to host defenses.

    2. Toxin production.

      1. Endotoxins.

      2. Exotoxins.

      3. Enterotoxins.

  4. The Spread of Pathogens.

    1. Some examples of methods:

      1. Direct contact with individuals (with active disease or in carrier state)
      2. Food
      3. Water
      4. Soil
      5. Fomites (clothing, toys, bedding, tools, implements, etc.)
      6. Air
      7. Insects
      8. Mites & ticks

    2. Preventing the Spread of Pathogens.

      1. Control of insects, mites, ticks and protection against them.

      2. Treatment of sewage.

      3. Control of human carriers.

      4. Sanitation/sterilization of foods, water, infected materials.

      5. Slaughter and disposal of infected animals; destruction of infected plants.

      6. Ventilation, air purification.

      7. Adequate treatment of hosts.

      8. Breeding resistant strains or varieties.

      9. Quarantine.

  5. Host defense against pathogenic microorganisms.

    1. Natural (constitutive) defense.

      1. Skin and mucous membranes.

      2. Microbicidal substances.

        1. Lysozyme.

        2. Interferon.

        3. Complement.

      3. Normal flora.

      4. Inflammation and phagocytosis.

    2. Immune (inducible) defense.

      1. Two types of acquired immunity.

        1. Active.

        2. Passive.

      2. Antigens and antibodies.

        1. Definition of an antigen.

        2. Examples of antigens.

        3. Definition of an antibody.

        4. How antibodies protect host.

      3. Artificial immunization.

        1. History of "vaccination."

        2. Active: vaccine and toxoid.

        3. Passive: antitoxin, antiserum and immunoserum.

        4. Current and future vaccination procedures.

PART TWO – INFECTIOUS DISEASES

  1. Human Diseases.

    1. Examples. (* = in table below)

      1. Caused by invasive bacteria:  tuberculosis (Mycobacterium tuberculosis), bacterial pneumonia (Klebsiella pneumoniae, Streptococcus pneumoniae), cholera (Vibrio cholerae), Legionnaire's disease*, Lyme disease*, whooping cough (Bordetella pertussis), gonorrhea (Neisseria gonorrheae), meningitis (Neisseria meningitidis), strep throat (Streptococcus pneumoniae), gastric ulcers (Helicobacter pylori), gastrointestinal infections*, typhoid fever*, bubonic/pneumonic plague (Yersinia pestis). Also dental caries, boils, pimples, abscesses.

      2. Caused by toxigenic bacteria:  anthrax*, tetanus (Clostridium tetani), diphtheria (Corynebacterium diphtheriae), botulism*, staphylococcal food poisoning*, toxic shock syndrome (Staphylococcus aureus), hemolytic-uremic syndrome.*

      3. Caused by viruses:  common cold, influenza, viral pneumonia, measles, rubella, mumps, chickenpox, smallpox, poliomyelitis, herpes, hepatitis, AIDS, hantavirus pulmonary syndrome.

      4. Caused by fungi & protozoa (covered earlier):  blastomycosis, histoplasmosis; malaria, trypanosomiasis (sleeping sickness), amoebic dysentery, giardiasis, cryptosporidiosis.

    2. Some specific human diseases caused by bacteria:
    disease causative agent bacterial characteristics transmission symptoms
    Clostridium perfringens food infection Clostridium perfringens gram-positive, strictly anaerobic, endospore-forming rod food-borne cramps, diarrhea
    Staphylococcus aureus food poisoning Staphylococcus aureus gram-positive, facultatively anaerobic coccus food-borne toxin rapid onset of nausea, vomiting and cramping
    Salmonella food infection (gastroenteritis) many Salmonella serotypes gram-negative, facultatively anaerobic rod food-borne cramps, nausea, vomiting, diarrhea
    Typhoid fever Salmonella serotype Typhi gram-negative, facultatively anaerobic rod food, water  
    Shigellosis Shigella gram-negative, facultatively anaerobic rod food, water dystentery (bloody diarrhea)
    Hemolytic-uremic syndrome Shiga toxin-producing strains of Shigella and E. coli gram-negative, facultatively anaerobic rod food, water anemia, kidney failure, nervous system injury
    Anthrax Bacillus anthracis gram-positive, facultatively anaerobic, endospore-forming rod food, inhalation, through opening in skin tissue swelling, hemorrhage, circulatory failure
    Lyme disease Borrelia burgdorferi gram-negative, microaerophilic spirochete ticks (mice and deer are among the animal reservoirs) stage I: rash, flu-like symptoms with fever & chills, joint pains; stage II: acute effects on heart and nervous system; stage III: chronic arthritis and impairment of the nervous system
    Legionnaire's disease Legionella gram-negative rod water flu-like symptoms leading to major complications

  2. Animal Diseases.

    1. Examples. (* = in table below)

      1. Caused by bacteria:  brucellosis*, mastitis*, tuberculosis*, Johne's disease (Mycobacterium paratuberculosis), anthrax*, Salmonella infections*, actinomycosis (Actinomyces israelii), scours, foot rot.

      2. Caused by viruses:  foot and mouth disease (covered earlier), hog cholera, Newcastle disease of poultry, rabies, pseudorabies of swine, canine distemper.

      3. Caused by prions (covered earlier):  mad cow disease, scrapie of sheep.

    2. Prevention and control.

      1. Sanitation and confinement.

      2. Vaccination.

      3. Antibiotics.

      4. Quarantine.

    3. Some specific animal diseases caused by bacteria:
    disease causative agent bacterial characteristics transmission symptoms
    Brucellosis,
    Bang's disease,
    undulant fever    		 species of Brucella gram-negative rod directly thru mucous membranes, skin abrasions, ingestion of infected milk affects cattle, dogs, goats, pigs, humans, bison, elk, moose, caribou & reindeer; affects mammary glands & uterus in animals; in humans causes recurring fevers and may lead to bone infection
    Mastitis Staphylococcus aureus, Streptococcus agalactiae gram-positive cocci (S. aureus = fac. anaerobe; Strep. agalactiae = aerotolerant anaerobe) direct contact infection of mammary glands
    Tuberculosis
    (bovine)    		 Mycobacterium bovis gram-positive, strictly aerobic, acid-fast rod ingestion (transmitted to humans in milk) infection and tissue nodulation in intestinal tract, lymph nodes, bones & joints
    Anthrax Bacillus anthracis gram-positive, facultatively anaerobic, endospore-forming rod as for humans (above table)
    Salmonella
    diseases of
    poultry    		 Salmonella serotypes Pullorum and Gallinarum (would be classified as one serotype, but different biochemical reactions and disease symptoms require separation) gram-positive, facultatively anaerobic, endospore-forming rod direct contact and transmission thru eggs/into embryos pullorum disease: high mortality with white diarrhea in young chicks & poults; fowl typhoid: high mortality with yellow diarrhea in young and adult poultry

  3. Plant Diseases.

    1. Examples.

      1. Caused by bacteria:  soft rots (Erwinia) and wilts (Erwinia, Pseudomonas, Burkholderia, Ralstonia, Xanthomonas) of vegetables, galls (Agrobacterium tumefaciens), common potato scab (Streptomyces scabies).

      2. Caused by viruses and viroids:  mosaic diseases of cucumber, potato and bean; also peach yellows, aster yellows, curly top of sugar beets, potato spindle tuber viroid.

      3. Caused by fungi:  late blight of potato, powdery mildews, corn smut, Dutch elm disease, cereal rusts, white pine blister rust.

      4. Caused by abiotic factors:  nutritional deficiencies, mineral toxicities, toxicity due to pollutants (including pesticides).

    2. Prevention and control.

      1. Difficulties in controlling bacterial plant diseases.

        1. Organisms often overwinter in protected places.

        2. They can spread rapidly through direct contact.

        3. They can spread in wind.

        4. They can enter damaged plants fast.

        5. They can multiply rapidly once in compatible host.

      2. Sanitation.

      3. Crop-rotation.

      4. Chemical treatment.

      5. Development of resistant varieties.

      6. Elimination of insect vectors.

    3. Symptoms of plant diseases caused by bacteria.


      Generalized Diagram of Plant Diseases.

      1. Rots.

      2. Wilts.

      3. Leaf spots and blights.

      4. Cankers and blights of woody tissue.

      5. Galls.

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Page last modified on
3/9/05 at 3:30 PM, CST.
John Lindquist, Dept. of Bacteriology,
University of Wisconsin – Madison