Flashcards in Chapter 14 Deck (82)
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pathology - also etiology & pathogenesis
scientific study of disease, including etiology (cause), pathogenesis (way a disease develops) and the structural and functional changes and their effects on the body caused by the disease.
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etiology
the cause of a disease
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pathogenesis
the way a disease develops
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pathogen
disease-causing microorganism
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infection
invasion and growth of pathogens in the body causing signs of illness, inflammation, and tissue damage
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colonization
the presence and growth of microorganisms WITHOUT signs or symptoms
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disease
abnormal state in which body is not performing its normal functions
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normal microbiota/flora & locations
microorganisms that reside permanently in or on the body but do not cause disease under normal conditions.
LOCATIONS include skin, eyes, nose/throat, mouth, large intestine, urinary and reproductive systems
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Normal microbiota: Skin
sweat & oil glands
keratin
moisture content
Most microbes don't become residents because secretions from sweat & oil glands have antimicrobial properties.
Keratin is also a resistant barrier, and low pH of skin inhibits many microbes.
Also, skin has a relatively low moisture content.
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Normal microbiota: Eyes
conjunctiva
tears/blinking
Conjunctiva is the continuation of the skin or mucous membrane, contains the same microbiota found on skin.
Tears and blinking eliminate some microbes or inhibit others from colonizing.
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Normal microbiota: Nose/throat
microbial antagonism
nasal secretion
mucus/ciliary action
Although some normal microbiota are potential pathogens, their ability to cause disease is reduced by microbial antagonism.
Nasal secretions kill or inhibit many microbes, and mucus and ciliary action remove many microbes.
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Normal microbiota: Mouth
Moisture, warmth, presence of food
biting, chewing, tongue movements, salivary flow
saliva
Moisture, warmth, and constant presence of food make the mouth an ideal environment that supports very large and diverse microbial populations on the tongue, cheeks, teeth and gums.
Biting, chewing, tongue movements, and salivary flow dislodge microbes.
Saliva contains several antimicrobial substances
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Normal microbiota: Large intestine
largest
mucus/shedding
mucosa
diarrhea
contains largest # of resident microbiota in the body b/c of available moisture and nutrients.
Mucus & periodic shedding of the lining prevent many microbes from attaching to the lining of the gastrointestinal tract, and mucosa produces several antimicrobial chemicals.
Diarrhea also flushes out some of the normal microbiota.
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Normal microbiota: Urinary and Reproductive systems
urethra
vag
mucus/shedding
cilia/mucus
Lower urethra in both sexes has resident population.
Vag has its acid-tolerant population of microbes b/c of the nature of its secretions.
Mucus and periodic shedding of the lining prevent microbes from attaching to the lining; urine flow mechanically removes microbes, and pH of urin and urea are antimicrobial.
Cilia and mucus expel microbes from cervix into the vag, and acidity of the vag inhibits or kills microbes.
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transient microbiota
microorganisms that are present in or on the body for a period of time and then disappear
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microbial antagonism/competitive exclusion
CCSS
by competing for resources and/or producing bacteriocins, the normal microbiota protect the host by preventing the colonization and overgrowth of harmful microorganisms.
Includes Candida albicans, Salmonella, Shigella, Clostridium difficile
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Microbial antagonism: Candida albicans
normal bacterial microbiota of the human vag is ~pH=4.
Presence of the normal bacterial microbiota inhibits growth of Candida albicans, which grows when balance between normal microbiota and pathogens is upset, and when pH is altered.
If population is eliminated by antibiotics, excessive douching, or deodorants, pH of vag reverts to neutral and C. albicans can flourish and become dominant microorganism there, which leads to vaginitis.
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Microbial antagonism: E. coli
Produces bacteriocins (inhibits growth of other bacteria of same or related species such as pathogenic Salmonella and Shigella).
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Microbial antagonism: Clostridium difficile
Normal microbiota of the large intestine effectively inhibit C. difficile, but if normal microbiota is eliminated (antibiotics), C. difficile can be a problem.
This microbe is responsible for nearly all gastrointestinal infections that follow antibiotic therapy, from mild diarrhea to sever or even fatal colitis (inflammation of colon).
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Symbiosis
relationship between 2 organisms in which at least 1 organism is dependent on the other, such as the normal microbiota and the host.
Includes commensalism, mutualism, parasitism
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Symbiosis: commensalism
one of the organisms BENEFITS, the other is unaffected.
EX: S. epidermidis on the surface of the skin (only bacteria benefits)
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Symbiosis: mutualism
both organisms BENEFIT.
EX: E. coli in the large intestine.
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Symbiosis: parasitism
one organism benefits at the expense of the other (many disease causing bacterias)
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Opportunistic pathogens
Do not cause disease in their normal habitat in a healthy person; may cause disease IF it gains access to other sites of the body, IF the host is weakened, IF they are present in large #s
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List Koch's postulates
Demonstrate a specific pathogenic microorganism is the cause of a specific disease.
1. pathogen must be present in every case of the disease.
2. pathogen must be isolated from the disease host and grown in pure culture.
3. the cultured pathogen must cause the disease when inoculated into a healthy, susceptible host.
4. same pathogen must be isolated from the inoculated host.
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symptom
changes in body function; not apparent to an observer
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signs
objective changes the physical can observe and measure
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syndrome
specific group of symptoms and signs accompany a particular disease
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communicable disease
disease that spreads from one host to another, directly or indirectly
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contagious diseases
disease that easily spreads from one person to another.
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noncommunicable disease
ex
disease that does not spread from one host to another: it is caused by one's own microbiota (pnemonias), or when external microorganisms are introduced into the body (Clostridium tetani)
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incidence
#
common
probability
1. number of NEW cases of a disease in a population during a particular time period;
2. indicates how common a disease occurs during the time period;
3. indicator of a person's probability of developing the disease during the time period
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prevalence
#
proportion
impact of disease on a population
probability of having the disease
1. the TOTAL number of cases of a disease in a population at a specific time (either time point or time period);
2. represents the proportion of population with the disease;
3. useful for assessing the impact of a disease on a population and a person's probability of having a disease.
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sporadic disease
occurs occasionally;
ex: typhoid fever in the US
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endemic disease
constantly present in a population; ex: common cold
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epidemic disease
many people in a given area get it in a relatively short period of time;
ex: influenza
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pandemic disease
epidemic disease that occurs worldwide
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acute disease
develops rapidly but does not last
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chronic disease
develops slowly and may last or recur for a long time
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subacute disease
intermediate between acute and chronic diseases
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latent disease
disease that the pathogen remains inactive for a period of time before becoming active
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herd immunity
when the majority of a population have immunity against an infectious disease, the chance of the nonimmunized individuals to contract the disease is little: "community immunity"
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local infection
invading microorganism are limited to a small area of the body
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systemic infection
microorganism or their products are spread throughout the body by the blood or lymph
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focal infection
infection originated from a local infection, later the pathogen or its products spread from local infection area to the other parts of the body
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sepsis
toxic inflammatory condition arising from the spread of microbes
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septicemia
blood poisoning, systemic infection arising from multiplication of pathogens in the blood; common example of sepsis.
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bacteremia
presence of bacteria in the blood
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toxemia
presence of toxins in the blood
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viremia
presence of viruses in the blood
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primary infection
acute infection that causes the initial illness
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secondary infection
caused by opportunistic pathogen after primary infection has weakened the body's defenses
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subclinical (inapparent) infection
inapparent infection; does not cause any noticible disease
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5 sequential stages of infectious diseases
IPIDC -->
incubation period,
predromal period,
period of illness,
period of decline,
period of convalescence.
Patient can be infectious during every stage; infections can be spread even during incubation and convalescence.
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incubation period
interval btw initial infection and first appearance of signs or symptoms
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prodromal period
short period following the incubation period in some diseases; not all diseases have it; early, mild symptoms of disease, such as aches and malaise
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period of illness
most severe stage; apparent signs and symptoms of disease; usually when a patient goes to a physician; immune system has not fully responded to pathogens; WBCs may increase/decreases; treatments and patient's defense end of the period of illness, or patient dies during this period
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period of decline
signs and symptoms subside; immune response and products of imune response peak in this stage
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period of convalescence
tissues repaired; patient regains strength and recovers
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reservoir of infection
sites, living or nonliving, where pathogens are maintained as a continual source of illness. 3 types: Human, animal and nonliving
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Human reservoir
HUMAN: people with signs and symptoms or carriers (show no sign of illness);
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Animal reservoir
ANIMAL: zoonoses are diseases transmitted from animals to humans;
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Nonliving reservoir
NONLIVING: soil, water, foods
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3 principle routes of disease transmission; examples
contact, vehicle, vector
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direct contact transmission; examples
person-to-person physical contact; touching, kissing, sex.
Common diseases: cold, flu, staph infections, hep A, measles, STDs
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indirect contact transmission; examples
mediated through a nonliving object called a fomite.
Examples: tissues, handkerchiefs, towels, bedding, diapers, drinking cups, eating utensils, toys, money, thermometers. AIDS, hep B, tetanus
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droplet transmission; examples
Microbes in droplet nuclei (mucus droplets) discharged through coughing, sneezing, talking, etc.
Travels <1 meter.
Examples: cold, flu, pneumonia, pertussis (whooping cough)
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waterborne; examples
spread by water contaminated with untreated/poorly treated sewage.
EX: cholera
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foodborne; examples
transmitted in foods incompletely cooked, poorly refrigerated, or prepared under unsanitary conditions.
EX: food poisoning, tapeworm manifestation
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airborne; examples
spread of agents of infection by droplet nuclei in dust that travel > 1 meter from reservoir to host.
EX: measles, tuberculosis
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vector transmission; examples
animals that transmit diseases from one host to another. - mechanical or biological transmission
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mechanical transmission; examples
passively carries the pathogens such as on insect's feet or other body parts. Generally not a host for the multiplication of the pathogen (vs biological transmission)
EX: housefly can transfer pathogens of typhoid fever and bacillary dysentery (shigellosis) from feces of infected people to food
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biological transmission; examples
transmit pathogens and serves as host for the multiplication of pathogens.
EX: arthropod bites infected person or animal and ingests infected blood. Pathogen reproduces in vector, increasing the number of pathogens which increases possibility that it will be transmitted to another host.
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nosomial infection
infection acquired in hospital, nursing home, health care facilities.
Does not show any evidence of being present or incubating at the time of admission to a hospital; it is acquired as a result of the hospital stay. Important to wash your hands.
Nosocomial infections generally result from:
microorgs in the hospital environment,
compromised/weakened status of host,
and chain of transmission in the hospital.
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emerging infectious disease
new or changing, showing an increase in incidence recently or potentially in the near future.
75% of EIDs are zoonotic, viral, and vector-borne
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epidemiology
3 investigators SSN
3 types of investigation DAE
study of when and where diseases occur and how they are transmitted in populations.
3 investigators: John Snow, Ignas Semmelweis, Florence Nightingale.
3 types of investigation: descriptive, analytical, experimental
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descriptive epidemiology
collect all data that describe occurrence of the disease
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analytical epidemiology
analyze a particular disease to determine its probable cause, mode of transmission, and possible means of prevention
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experimental epidemiology
test a hypothesis concerning the cause of a disease
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morbidity
incidence of specific notifiable diseases
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mortality
number of deaths from these diseases
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