1. Microorganisms and Disease
How does the human body and various microorganisms interact in terms of disease?

2. Infectious Disease skin, mucous membranes, antibodies
bacteria can produce capsules, enzymes, and toxins
infectious disease is the primary cause of death world-wide
: influenza pandemic killed more than 20 million people world-wide and 500,000 people in the United States

3. Readings question #1:
Describe the “chain of infection”.

4. Infection vs. Disease
Infection: “the entry, establishment and multiplication of pathogenic organisms within a host”
Disease: an abnormal state in which part or all of the body is not properly adjusted or is incapable of performing normal functions; any change from a state of health

5. Factors that Influence the Occurrence of Disease
1) virulence of the organisms
2) portal of entry of the pathogen
3) number of organisms present
4) the resistance of the host

6. 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”

7. 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”

8. 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”

9. MRSA
Methicillin-resistant Staphylococcus aureus

10. MRSA 2005: 94, 360 people; 18,650 died (CDC)
85%- healthcare % outside of hospital
“colonized” but not infected
invasive medical procedures, weakened immune systems
sepsis, surgical site infections, pneumonia

11. MRSA (cont’d) mode: human hands
staph generally harmless unless they enter through a cut or wound
1990: CA-MRSA (community-associated)
preventable

12. Types of Infections and Diseases
exogenous infections: “originating outside an organ or part”
endogenous infections: “produced or arising from within a cell or organism”
acute diseases: symptoms develop rapidly but may only last for a short period of time
chronic diseases: develop slowly and are likely to continue or recur for long periods of time

13. Infections and Diseases (cont’d)
communicable diseases: “a disease that may be transmitted directly or indirectly from one individual to another”
endemic: “disease that occurs continuously in a particular region, but has low mortality”
epidemic: “appearance of an infectious disease or condition that attacks many people at the same time in the same geographical area”

14. Infections and Disease (cont’d)
pandemic: “a disease affecting the majority of the population of a large region or one that is epidemic at the same time in many different parts of the world”
sporadic: “a disease which occurs occasionally or in scattered instances”
noncommunicable diseases: do not spread from one host to another

15. Readings question #2:
Define local, focal, and general infections, and give an example of each.

16. 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

17. Readings question #3:
Define septicemia and toxemia and include an example of each. What are the symptoms/characteristics for septicemia and toxemia?

18. Factors Influencing Virulence
Readings question #4:
Describe toxins, exotoxins, and endotoxins, and give an example of each.
Capsules and Endospores

19. Sources of Infection Human Reservoirs: “carriers”
Universal Precautions
Animal Reservoirs: “zoonoses”
Environmental Reservoirs: Vibrio cholera
Salmonella typhi

20. 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 #5: Describe the primary mechanisms of indirect contact. Include examples with each mechanism.
What are fomites?

21. Portal of Entry 5 portals of entry: 1) skin and mucous membranes
2) respiratory tract
3) digestive tract
4) genito-urinary tract
5) placenta

22. Skin and Mucous Membranes
membranes line the respiratory tract, gastrointestinal tract, genitourinary tract, and conjunctiva
skin is one of the largest organs of the body
- hair follicles and sweat gland ducts
parenteral route: microorganisms are deposited directly into the tissues

23. Respiratory Tract easiest and most frequently traveled portal of entry
airborne pathogens
sneezing, coughing, touching contaminated surfaces and then touching the mouth or nose, dust particles
pathogenic bacterial spores may be inhaled

24. Digestive Tract Food, water, contaminated fingers
HCl and enzymes in the stomach
bile and enzymes in the small intestine
poliomyelitis, hepatitis A, typhoid fever, amoebic dysentery, giardiasis, shigellosis, cholera

25. Genitourinary Tract pathogens that are contracted sexually
genital warts, chlamydia, herpes

26. Placenta CMV: cytomegalovirus
10% infants: premature delivery, jaundice, enlarged liver and spleen, microcephaly, seizures, rash, feeding difficulties
hearing, vision, neurologic, and developmental problems
no vaccine
hand washing, not sharing eating utensils, avoid kissing or intimate contact with CMV+

27. Portals of Exit secretions, excretions, discharges, shed tissue
related to the infected part of the body
microbe generally uses the same portal for entry and exit
respiratory: TB, whooping cough, pheumonia, scarlet fever, meningococcal meningitis, chickenpox, measles, mumps, small pox, influenza

28. Portals of Exit (cont’d)
gastrointestinal: feces- salmonellosis, cholera, typhoid fever, shigellosis, amoebic dysentery, poliomyelitis
saliva - rabies, mumps, infectious mononucleosis
genitourinary: secretions from penis and vagina- STDs
urine- tyhphoid fever brucellosis

29. Portals of Exit (cont’d)
skin or wound infections - impetigo, skin ringworm, herpes simplex, warts
Infected blood: insects, contaminated needles and syringes
insects – yellow fever, plague, tularemia, malaria
con. needles & syringes – AIDS, hepatitis B

30. Number of Organisms Present
Third factor

31. Resistance of the Host mechanical defenses physiological defenses
chemical defenses

32. Mechanical Defenses
Skin: epithelium (epidermis), sebaceous glands, dryness, “necrobiosis”
Eyes: lacrimal apparatus
Saliva: cleansing action
Respiratory Tract: mucus, ciliated epithelium
Urinary Tract: flushing action

33. Physiological Defenses
Inflammation: pus
Fever: degrees
Phagocytosis: phagocyte ingests material

34. 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

35. 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

36. 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.”

37. 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

38. Types of Immunity Natural (Innate)
Acquired: Naturally Acquired – active, passive
Artificially Acquired
- active: vaccines passive: antibodies
immune serums

39. 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