Transcript Microorganisms and Disease

Microorganisms and Disease
How does the human body and
various microorganisms interact in
terms of disease?
Infectious Disease
• skin, mucous membranes, antibodies
• bacteria can produce capsules, enzymes, and
toxins
• infectious disease is the primary cause of
death world-wide
• 1918-1919: influenza pandemic killed more
than 20 million people world-wide and
500,000 people in the United States
• Readings question #1:
Describe the “chain of infection”.
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
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
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”
MRSA
• Methicillin-resistant Staphylococcus aureus
MRSA
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2005: 94, 360 people; 18,650 died (CDC)
85%- healthcare
66% outside of hospital
“colonized” but not infected
invasive medical procedures, weakened
immune systems
• sepsis, surgical site infections, pneumonia
MRSA (cont’d)
• mode: human hands
• staph generally harmless unless they enter
through a cut or wound
• 1990: CA-MRSA (community-associated)
• preventable
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
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”
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
• Readings question #2:
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 #3:
Define septicemia and toxemia and include an
example of each. What are the
symptoms/characteristics for septicemia and
toxemia?
Factors Influencing Virulence
• Readings question #4:
Describe toxins, exotoxins, and endotoxins, and
give an example of each.
Capsules and Endospores
Sources of Infection
• Human Reservoirs: “carriers”
Universal Precautions
• Animal Reservoirs: “zoonoses”
• Environmental Reservoirs: Vibrio cholera
Salmonella typhi
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?
Portal of Entry
• 5 portals of entry:
1) skin and mucous membranes
2) respiratory tract
3) digestive tract
4) genito-urinary tract
5) placenta
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
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
Digestive Tract
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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
Genitourinary Tract
• pathogens that are contracted sexually
• genital warts, chlamydia, herpes
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+
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
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
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
Number of Organisms Present
• Third factor
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