Transcript Microorganisms and Disease

Microorganisms and Disease
How does the human body and
various microorganisms interact in
terms of disease?
Virulence of Organisms
• virulence: “relative power of an organism to
produce disease”
• resistance
• host
• pathogen
• contamination: “the act of introducing
disease germs or infectious material into an
area or substance”
Virulence (cont’d)
• true pathogen: “an organism that due to its
virulence is able to produce disease:
• attenuation: “dilution or weakening of
virulence of a microorganism, reducing or
abolishing pathogenicity”
• pathogenicity: “the state of producing or
being able to produce pathological changes
and disease”
Virulence (cont’d)
• indigenous flora: “synonymous with normal
flora, indicates the microbial population that
lives with the host in a healthy condition”
• opportunists: “an organism that exists as part
of the normal flora but may become
pathogenic under certain conditions”
• drug-fast: “resistant, as in bacteria, to the
action of a drug or drugs”
• Readings question #1:
Define local, focal, and general infections, and give
an example of each.
Infections (cont’d)
• primary: “the first infection that a host has
after a period of health”
• secondary: “infection caused by a different
organism than the one causing the primary
infection
• mixed: “infection caused by two or more
organisms”
• blood: viremia; bacteremia
• Readings question #2:
Define septicemia and toxemia and include an
example of each. What are the
symptoms/characteristics for septicemia and
toxemia?
Factors Influencing Virulence
• Readings question #3:
Describe toxins, exotoxins, and endotoxins, and
give an example of each.
Capsules and Endospores
Transmission of Infections
• Direct: viral respiratory disease, staphylococcal
infections, hepatitis A, measles, scarlet fever,
STDs, AIDS, infectious mononucleosis
- hand washing, gloves etc.
• Indirect:
Readings question #4: Describe the four
primary mechanisms of indirect contact.
Include examples with each mechanism.
What are fomites?
• Readings question #5:
• What is a vector? What are biological and
mechanical vectors? Give an example of each.
Resistance of the Host
• mechanical defenses
• physiological defenses
• chemical defenses
Mechanical Defenses
• Skin: epithelium (epidermis), sebaceous
glands, dryness, “necrobiosis”
• Eyes: lacrimal apparatus
• Saliva: cleansing action
• Respiratory Tract: mucus, ciliated epithelium
• Urinary Tract: flushing action
Physiological Defenses
• Inflammation: pus
• Fever: 102-104 degrees
• Phagocytosis: phagocyte ingests material
Chemical Defenses
• Lysozome: enzyme that breaks down cell
walls of gram-positive bacteria and some
gram-negative bacteria
• Sebum: sebaceous glands, oily substance,
protective film, lowers skin pH
• Gastric Juice: HCl, enzymes, mucus, acidic
• Interferon: eukaryotic cells, surface receptors
Immunology
• Latin immunis “to exempt”
• Why is it that some people tend to be sick
more often than others?
• Why can two people eat the same infected
chicken, and only one person contracts food
poisening?
• children, elderly, immunocompromised
Antigens
• “a foreign substance that stimulates the
formation of antibodies that react specifically
with it”
• substance that provoke a specific response
• Antibodies: “glycoprotein substance
developed by the body in response to, and
interacting specifically, with an antigen. Also
known as immunoglobulin.”
Antigen-Antibody Reactions
• 1) destroy pathogens by neutralizing the
toxins the pathogen produces
• 2) coat the pathogen with a substance that
attracts phagocytes by forming a substance
that clumps the antigens together
• 3) prevent the pathogen from adhering to the
body’s cells
Types of Immunity
• Natural (Innate)
• Acquired: Naturally Acquired – active, passive
Artificially Acquired
- active: vaccines
- passive: antibodies
immune serums
Hypersensitivity
(Allergy)
• “an acquired, abnormal immune response to a
substance (allergen) that does not normally
cause a reaction”
• Immediate: 2 – 30 minutes
– systemic (shock, breathing difficulties)
– Localized (hay fever, asthma, hives)
• Delayed: 1-2 days
– TB skin test, contact dermatitis