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What does it take to get an infection? What are some things required to get one?
- Infection- a condition in which pathogenic microbes penetrate host defenses, enter tissues, adn multiply
- 1. contact - microbes adhere to exposed body surface
- 2. colonization with flora
- 3. invasion - microbes cross lines of defense and enter sterile tissue
- 4. infection - pathogenic microbes mulitply in the tissues
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What are other terms/words used to describe flora?
- Most areas of the body in contact with the outside enviornment harbor resident microbes; Internal organs, tissues, and fluids are microbe-free
- Transients - microbes that occupy the body for only short periods of time
- Residents - microbes that become established
- Indingenous flora
- Microflora
- Biota
- Commensuals
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In order to get an endogenous infection, what has to occur?
They occur when normal flora is introduced to a site that was previously sterile
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When do you start picking up germs? (as part of life in normal flora)
- Uterus and contents are normally sterile and remain so until just before birth
- Breaking of fetal membrane exposes the infant; all subsequent handling and feeding continue to introduce what will be normal flora
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Where can you find resident flora?
- Skin is the largest and most accessible organ
- 2 cutaneous populations. Transients - influences by hygiene and Resident - stable, predicatable, less influenced by hygeine.
- Can also find in GI tract, upper respiratory tract, genital tract, urinary tract, eyes and ears
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What are some of the virulence factors? Examples
- Virulence factors - traits used to invade and establish themselves in the host, also determine the degree of tissue damage that occurs, severity of disease. Any characteristic or structure of a microbe that contributes to the disease state.
- Exoenzymes - dissolve extracellular barriers and penetrate through or between cells
- Toxigenicity - capacity to produce toxins at the site of multiplication. 1. Endotoxin - toxin not secreted but is released after the cell is damaged. 2. Exotoxin - toxin molecule secreted by a living bacterial cell into the infected tissue
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Know the stages of illness. 4 Stages
- 1. Incubation period - time from the initial contact w/ the infectious agent to the appearance of first symptoms; agent is multiplying but damage is insufficent to cause symptoms; several hours to several years
- 2. Prodromal stage - vague feelings of discomfort; nonspecific complaints
- 3. Period of invasion - multiples at high levels, becomes well-established; more specific signs and symptoms
- 4. Convalescent period - as person begins to respond to the infection, symptoms decline
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Localized infection, Secondary infection, mixed infection and acute infection?
- 1. Localized infection - microbes enter the body and remains confined to a specific tissue
- 2. Secondary infection - another infection by a different microbe
- 3. Mixed infection - several microbes grow simultaneously at the infection site
- 4. Polymicrobial
- 5. Acute infection -comes on rapidly, with severe but short-lived effects
- 6. Systematic infection - infection spreads to several sites and tissue fluids usually in the bloodstream
- 7. Focal infection - when infetious agent breaks loose from a local infection and is carried to other tissues
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What's the definition of a sign? Symptoms?
- Earliest symptoms of disease as a result of the activation of the body defenses. Fever, pain, soreness and swelling
- Signs of inflammation
- Edema - accumulation of fluid
- Granulomas and abscesses - walled-off collections of inflammatory cells and microbes
- Lymphadenitis - swollen lymph nodes
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What's a syndrome?
When a disease can be identified or defined by a collection of signs or symptoms
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What are the signs of inflammation?
- Edema - accumulation of fluid
- Granulomas and abscesses - walled-off collections of inflammatory cells and microbes
- Lymphadenitis - swollen lymph nodes
- Fever, pain soreness and swelling
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Know what immunology is? Epidemiology is?
- Immunology - the study of body's second and third lines of defense
- Epidemiology - the study of the frequency and distribution of disease and health-related factors in human populations
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What is W.H.O?
- World Health Organization
- Specialized agency of the United Nations that acts as a coordinating authority on internationl public health
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What is CDC?
- Center for Disease Control and Prevention
- A Federal agency in the Dept of Health and Human Services; located in Atlanta -investigates and diagnoses and tries to control or prevent diseases
- (esp new and unusual diseases)
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What is incidence rate? Prevalence rate?
- Incidence - a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period.
- Prevalence - which is a measure of the total number of cases of disease in a population, rather than the rate of occurrence of new cases
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17. What are things like endemic, how is that different from epidemic? Or pandemic?
- Endemic - disease that exhibits a relatively steady frequency over a long period of time in a particular geographic locale
- Sporadic - when occasional cases are reported at irregular intervals
- Epidemic - when prevalence of a disease is increasing beyond what is expected
- Pandemic - epidemic across contients
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What is a reservoir?
- Primary habitat of pathogen in the natural world.
- Human or animal carrier, soil, water, plants
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A carrier of fomite?
- Carrier - an individual who inconspicuously shelters a pathogen and spreads it to others; may or may not have experienced disease due to the microbe
- Fomite - any inanimate object/substance capable of carrying infectious organisms and hence transferring them from one individual to another. It can be anything from a cloth to a mop head.
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Difference between carrier and vector?
- Carrier - an individual who inconspicuously shelters a pathogen and spreads it to others; may or may not have experienced disease due to microbe
- Vector - A live animal (other then human) that transmits an infectious agent from one host to another
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Whats the difference between aerosols and mechanical vectors?
- Aerosol - airborne infectious that are caused indirectly stuff like, TB, Influenza virus, hantavirus
- Mechanical - not necessary to the life cycle of an infectious agent and merely transports it without being infected
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Whats a drop of nuclei?
- Indirect contact pattern of transmission - passes from infected host to intermediate conveyor and then to another host
- Airborne - droplet of nuclei, aerosols
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What's a biological vector?
Biological vectors - actively participate in a pathogen's life cycle
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Know the different ports of entry, whats the most common?
Respiratory tract
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Know examples of the first line of defense
- Skin and mucous membranes of respiratory, urogenital, eyes and digestive tracts
- Outermost layer of skin is composed of epithelial cells compacted, cemented together and impregnated w/ keratin; few pathogens can penetrate if intact
- Flushing effect of sweat glands
- Damaged cells are rapidly replaced
- Mucous coat impedes attachment and entry of bacteria
- Blinking and tear production
- Stomach acid
- Nasal hair traps larger particles
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Know the difference between the first and second line of defense
- First line of defense - any barrier that blocks invasion at the portal of entry - nonspecific
- Second line of defense - protective cells and fluids; inflammation and phagocytosis - nonspecific
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For WBC's, know the different functions of it? Which are numerous and which are least?
- Neutrophils - 55-90% - lobed nuclei w/ lavender granules; phagocytes
- Eosinophils - 1-3% - orange granules and bilobed nucleus; destroy eukaryotic pathogens
- Basophils - 0.5% - constricted nuclei, dark blue granules; release potent chemical mediators. Mast Cells: nonmotile elements bound to connective tissue
- Lymphocytes - 20-35% - specific immunte response. B humoral immunity - activated B cells produce antibodies. T Cells - Activated T cells modulate immune functions and kill foreign cells.
- Monocytes, macrophages - 3-7% - largest of WBC's, kidneyshaped nucleus; phagocytic
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What is diapedesis? What is hemopoiesis?
- Diapedesis - migration of cells out of blood vessels into the tissues
- Hemopoiesis - production of blood cells
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What are plasma cells?
.92% water, metabolic proteisn, globulins, clotting factors, hormones, and all other chemicals and gases to support normal physiological functions
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What is the RES? What does it do?
- Reticuloendothelial System: network of connective tissue fibers that interconnects other cells and meshes with the connective tissue network surrounding organs.
- Inhabited by phagocytic cells - mononuclear phagocyte system - maacrophages ready to attack and ingest microbes that passed the first line of defense
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Know the different lymph organs, which ones are going to filter your blood?
- Spleen - structurally similar to lymph node; filters circulating blood to remove worn out RBC's and pathogens
- Thymus - high rate of growth and activity until puberty, then begins to shrink; site of T-cell maturation
- Lymph nodes - small, encapsulated, bean-shaped organs stationed along lymphatic channels and large blood vessels of the thoracic and abdominal cavities
- Misc - GALT, Peyers patch
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Inflammation, know the general properties of this
- Classic signs and symptoms characterized by:
- Redness - increased circulation and vaso dilation in injured tissues in response to chemical mediators and cytokines
- Warmth - heat given off by the increased blood flow
- Swelling - increased fluid escaping into the tissue as blood vessels dilate - edema; WBC's microbes, debris and fluid collecting to form pus; helping prevent spread of infection
- Pain - stimulation of nerve endings
- Possible loss of function
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What chemicals begin a fever response?
- Initiated by circulating pyrogens which reset the hypothalamus to increase body temperature; signals muscles to increase heat production and vasoconstriction.
- Exogenous pyrogens - products of infectious agents
- Endogenous pyrogens - liberated by monocytes, neutrophils, and marcophages during phagocytosis; interleukin-1 (IL-1) and tumor necrosis factor TNF
- Benefits of fever:
- Inhibits multiplication of temperature - sensitive microorganisms
- Impedes nutrition of bacteria by reducing the available iron
- Increases metabolism and stimulates immune reactions and protective physiological processes
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What is the third line of defense?
Third line of defense - acquired w/ exposure to foreign substance; produces protective antibodies creates memory cells - specific
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