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etiology, pathogenesis, infection, infectious disease
- etiology: study of cause of disease
- pathogenesis: development of disease
- infection: colonization of body by pathogen
- infectious disease: can be transmitted from one individual to another
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communicable disease, noncommunicable dissease, contagious disease
- communicable disease: can spread from one host to another
- noncommunicable dissease: not transmitted from one host to another
- contagious disease: easily spread from one host to another
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signs, symptoms, syndrome
- signs: change in body that can be measure or observed (fever, rash)
- symptoms: change in body function felt by the host
- syndrome: specific group of signs and symptoms that accompany a disease
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sporadic disease, endemic disease, epidemic disease, pandemic disease
- sporadic disease: occurs only occasionally in a population (Typhoid fever)
- endemic disease: constantly present in a population (common cold)
- epidemic disease: acquired by many hosts in a given area in a short time (influenza)
- pandemic disease: worldwide epidemic (AIDS)
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acute disease, chronic disease, subacute disease, latent disease
- acute disease: develop rapidly and lasts only a short time (influenza)
- chronic disease: develops slowly, less severe but lasts for a long time (TB, hep B) - typically more fatal
- subacute disease: intermediate between acute and chronic (sclerosing panencephalitis)
- latent disease: period of no symptoms when the pathogen is inactive (shingles
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local infection, systemic infection, focal infection
- local infection: limited to a very small area of the body (boils, abscesses)
- systemic infection: infection throughout body (measles)
- focal infection: systemic infection that began as local infection (gets into blood stream)
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bacterermia, septicemia, toxemia, viremia
- bacterermia: bacteria in blood stream
- septicemia: multiplication of pathogens in the blood stream
- toxemia: toxins in blood
- viremia: viruses in blood
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primary infection, secondary infection, subclinical infection
- primary infection: actue infection that causes initial illness
- secondary infection: opportunistic infection after a primary (predisposing) infection; more serious
- subclinical infection: no noticeable signs or symptoms (inapparent infection)
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Period of incubation, prodromal period, period of illness, period of decline, period of convalescence
- Incubation period: (no signs or symptoms) Time from which you are infected to when symptoms begin
- Prodromal period: (mild signs or symptoms) Begin to show signs/symptoms
- Period of illness: (most severe signs/symptoms) Sick, immune system kicks in
- Period of decline: (signs and symptoms) Occurs if body overcomes pathogen
- Period of convalescence: body returns to normal (days to weeks)
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Define/explain microbial antagonism
- Normal microbiota compete with pathogens to prevent overgrowth/infection
- Compete for nutrients, space (competitive exclusion - C. difficile completely line the GI tract so pathogens literally cannot attach)
- Produce substances harmful to invader (acids or bacteriocins)
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Describe symbiosis and the types
- Symbiosis: living together of two different organisms
- Commensalism: one organism benefits with the other is unaffected (Staphylococcus epidermidis on the skin)
- Mutualism: both organisms benefit (E. coli bacteria in the large intestine)
- Parasitism: one organism benefits while the other is harmed (H1N1 virus)
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Differentiate between normal flora and transient microbiota
- Normal microbiota
- Reside permanently in/on body [FOR LIFE]
- Normally do NOT produce disease
- Are aquired young (lactobacilli from vag, breathing, breast feeding, etc)
- Transient microbiota
- Present for a while then disappear [DAYS to YEARS]
- Normally do not produce disease (unless they go where they "aren't supposed to")
- Acquired from being kissed, touched, etc
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What is an opportunistic pathogen?
Normal microbiota do not causes disease in their normal habitat, but do so when in a different environment (Streptococcus epidermidis on skin is no big, but in cuts = you're fucked)
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List the locations of normal flora
- Nose
- throate
- lungs
- any air-exposed part of body
- eye
- mouth
- skin
- large intestine (MANY)
- small intestine (few)
- urinary tract
- reproductive system
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Discuss the benefits and possible dangers of normal flora including microbial antagonism/synergism
- Benefits
- Protects host by microbial antagonism (competitive exclusion)
- Synthesize B vitamins and K vitamins for host (we can't)
- Stimulate immune response (keeps it "sharp")
- Dangers
- Opportunism (cause disease in different habitat)
- Microbial synergism (two microbes act together to produce a greater effect eg. Streptococci and periodontal pathogens)
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Describe predisposing factors for disease
- Short urethra in females
- Inherited trades (sickle cell gene)
- Climate and weather (common cold)
- fatigue (stress)
- age (very young and very old are most susceptable)
- lifestyle
- chemotherapy
- antibiotic therapy
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Explain three general methods of disease transmission and give one example of each
- CONTACT
- Direct: requires close association or physical contact
- Indirect: spread by means of fomites
- Droplets: discharged from sneezing, coughing, etc
- VEHICLE - Transmission by inanimate reservoir
- Waterborne: sewage contaminated water
- Foodborned: incompletely cooked, poor storage, unsanitary conditions
- Airborne: droplets, dust, dirt
- VECTORS - Arthropods carry pathogens from one host to another
- Mechanical transmission: houseflies (typhoid fever, bacillary dysentery)
- Biological transmission: mosquitoes (malaria)
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List several methods of disease transmission in hospitals and explain how nosocomial infections can be prevented
- Direct contact: patient to patient, staff ot patient, visitors to patient
- Indirect contact: fomites, hospital venitalation system
- Nosocomial infections can be prevented by use of aseptic techniques, education about infection control, hand washing, and use of isolation rooms/wards
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List several approaches that will break the chain of transmission in an epidemic
- Remove reservoirs
- Water purification
- Vector control (insect, rodent, arthropod)
- Isolation
- Treat carriers
- Safe sex
- Proper food handling
- Hand washing (#1)
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List and describ Koch's postulates, their significance/applicibilty
- Koch's postulates demonstrate that a specific pathogen cause a specific disease
- 1. Microorganisms are isolated from a diseased or dead animal
- 2a. The microorganisms are grown in pure culture
- 2b. The microorganisms are identified
- 3. The microorganisms are injected into a healthy laboratory animal
- 4. Disease is reprooduced in a laboratory animal
- 5a. The microorganisms are isolated from this animal and grown in pure culture
- 5b. Microorganisms are identified (must be same as 2b)
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Describe the limitations to Koch's postulates
- Some causative agents cannot be cultured on existing articifical media (viruses, Micobacteria lepriae)
- Some diseases are not clear-cut (various pathogens causing similar signs and symptoms)
- Some pathogens may cause several disease conditions
- Infecting humans with infections agents is unethical, may not be pathogenic in other organisms
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Define reservoir. List/describe the types of reservoirs and portals of exit
- Reservoir of infection: continual source of pathogens
- Living
- Human: harbor and transmit pathogens to others; carriers (AIDS, gonorrhea)
- Animal: carry pathogens that causes disease in humans (rabies, lyme disease)
- *Zoonoses - animal diseases that may be transmistted to humans
- NONLIVING
- Soil: fungal (mycoses); bacterial (botulism, tetanus)
- Water: cause gastrointestinal infections (cholera, amoebic dysentary)
- Food: inadequately cooked, improperly prepared, or stored (Tricinella, food poisoning)
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List the 3 major determinantos of nosocomial infections
- Susceptibility of host (broken skin, compromised immune system)
- Microorganisms in hospital environment (reservoirs for pathogens, patients/staff/visitors, hospital microbes tend to be more resistant to drugs)
- Chain of transmission (direct contact between patients and staff, fomites)
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List and describe the sources of microorganisms involved in nosocomial infections
- Endogenous: patients themselves (touching a cut)
- Exogenous: staff, visitors, or other patients
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List and describe the common bacterial causes of nosocomial infections
- Urinary tract infections
- Surgical site infections
- Lower respiratory tract infections
- Bacteremia transmitted primarily by IV catheterizations
- Cutaneous infections
- Other
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Define epidemotiology, descriptive epidemiology, analytical epdimediology, experimental epidemiology
- epidemiology: Study of where and when diseases occur
- descriptive epidemiology: collection and analysis of data (mapped occurrence of cholera to a specific well in London)
- analytical epdimediology: comparison of a diseased group and a healthy group (improved sanitation decreased incidence of epidemic typhus)
- experimental epidemiology: controlled experiments (handwashing decreased incidence of puerperal fever)
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