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90 Cards in this Set
- Front
- Back
Normal.microbiota (normal flora) are organisms that |
–routinely reside on body’s surfaces |
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Relationship is delicate balance; |
•some can cause disease should opportunity arise (opportunistic) |
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Weaknesses or defects in innate or adaptive defenses |
•can leave individuals vulnerable to.invasion–Individuals said to be immunocompromised |
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Anatomical Barriers as Ecosystems |
•Skin, mucous membranes are barriers
–Also host complex ecosystem of microorganisms “living together” or symbiosis
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•Normal microbiota |
Resident microbiota and Transient.microbiota –Important to human health
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Resident microbiota inhabit |
sites for extended periods |
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Transient microbiota inhabit |
temporarily |
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Normal Microbiota havea protective role, Significant contribution is |
protection against pathogens |
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–protection against pathogens via |
•Covering of binding sites prevents attachment •Consumption of available nutrients •Production of compounds toxic to other bacteria |
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•Oral antibiotics can inhibit |
intestinal microbiota,allow overgrowth of toxin-producing Clostridium difficile.` |
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NormalMicrobiota also havea protective role via |
–Stimulation of adaptive immune system |
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–Stimulation of adaptive immune system |
•Mice reared in microbe-free environmenthave greatly underdeveloped mucosal-associated lymphoid tissue (MALT);antibodies against normal microbiota bind to pathogens as well |
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–Important in development of oraltolerance |
•Immune system learns to lessen response to many microbes that routinely inhabit gut as well as food–Basis of hygiene hypothesis, which proposes insufficient exposure to microbes can lead to allergies |
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–Healthy human fetus sterile until just before birth |
•Exposed to microbes during passagethrough birth canal •These take up residence; others fromfood, humans, environment soon also become established on newborn |
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–Composition of normal microbiotais dynamic |
Changes occur in response tophysiological variations within host (e.g., hormonal changes) and as result ofactivities of host (e.g., consuming food |
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•Westerndiet |
–characterized by high fat and renedcarbohydrate and sugar content –Correlated to increasing rate of obesity in the population –Sugar substitutes are also increasing (i.e., aspartame) |
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Gutmicrobiota from obese mice differs |
from lean mice |
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Wildtype(+/+) mouse |
•(consideredlean) |
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+/obmouse |
(consideredlean) |
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•ob/obmouse |
?????? |
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•ob is agenetic knockout that create a mice that is obese. |
–Consume more food–Have higher body fat content/weight |
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ob/ob mice have a different microbioat than |
+/+mice |
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ob/ob mice |
•Increasein the genus Firmicutes ,decrease in the genus Baceteriodetes
•Ob/ob miceare more efficient at harvesting energy from food |
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•An intestine from a person who consumes a Western-diet has a microbiome enriched in genes encoding pathways related |
–Phosphotransferase systems –Fructose and mannose metabolism, –Glycolysis/gluco-neogenesis, –But depleted of genes required for starch and sucrose metabolism •These changes may be associated with increase in energy entering into the host buthow?
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Shifting diversity/types of bacteria leads to increase energy uptake by host hypothesis |
•is that the ability to metabolizes and uptake fructose (a main sugar in Westerndiet) by bacteria is very low •This stimulates the the production of short chain fatty acids, which is sensed by the the human body •In response, the human body secretes leptin,which slows the movement of food through the intestine and activates fructose transporter •Leads to increased absorption of energy from food passing through intestine
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–Epidemiology |
•Howinfectious agents spread from person to person (place to place) Trackingthe spread of the disease •study of disease patterns in populations |
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–Infectious disease |
•Examining infections once they have occurred•Treating infection once they have occurred•Mechanistic understanding of both sides |
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Epidemiologists |
–collect,compile data about sources of disease and risk factors •Design infection control strategies,prevent or predict spread of disease •Use expertise in diverse disciplines including ecology, microbiology, sociology, statistics, and psychology •Many of our daily habits (handwashing, waste disposal) based on work |
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Two types of infectious agents in epidemiology |
•Communicable (contagious) diseases and •Non-communicable diseases |
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•Communicable (contagious) diseases |
–Transmitted from one host to another •e.g.,measles, colds, influenza –Transmission determined by interactionsbetween environment, pathogen, and host •Control of any of these factors may breakinfection cycle |
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•Non-communicable diseases |
–Do not spread from host to host
•Microorganisms most often arise from individual’s normal microbiota or environment |
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•Rates of Disease in a Population |
Attackrate Incidencerate Prevalence |
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Attack rate |
–is percentage of people who become ill inpopulation after exposure •Reflects infectious dose, immune statusof population |
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Incidencerate |
–is number of new cases/time/population •Measure of risk of an individualcontracting a disease |
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Prevalence |
–is total number of cases at any time orfor a specific period in a given population •Reflects overall impact of disease on society; includes old and new cases, as well as duration of disease Both expressed as cases per 100,000people |
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Morbidity |
–is incidence of disease in population atrisk•Contagious diseases (e.g., influenza)often have high morbidity rate: infected individual may transmit to several |
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Mortality |
–is overall death rate in population •In developed countries, most oftenassociated with non-communicable diseases (e.g., cancer, heart attack) •Communicable diseases major cause ofdeath in developing countries |
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Case-fatality rate |
–is percentage of population that diesfrom a specific disease
•Plague, Ebola feared because of very highrate |
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Endemicdiseases |
–constantly present in population•E.g., common cold, measles in UnitedStates |
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Epidemic |
–is unusually large number of cases •Can be from introduced or endemic disease |
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Outbreak |
–is group of casesat specific time and population |
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Pandemic |
–is global •(e.g., AIDS) |
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•Reservoirs of Infection |
–Natural habitat in which pathogen lives •In or on animal, human, or in environment(soil, water) •Identification important in disease control |
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–Human Reservoirs |
•May be exclusive or exist in other animals, environment •Often easier to control–E.g., smallpox
•Symptomatic or asymptomatic |
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Symptomatic infections |
obvious source of pathogens |
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Asymptomatic infections |
•harder to identify, may not realize, canspread to others –Up to 50% of women infected with Neisseria gonorrhoeae are asymptomatic, easily transmit –Many people carry Staphylococcus aureus |
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–Non-HumanAnimal Reservoirs |
•Zoonoses(zoonotic diseases) primarily exist in animals but can be transmitted to humans(e.g., plague, rabies) |
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–EnvironmentalReservoirs |
•Difficult or impossible to eliminate(e.g., Clostridium) |
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Mechanismsof transmission (2) |
Verticaltransmission and Horizontaltransmission |
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Verticaltransmission |
–is pregnant woman to fetus or mother toinfant during childbirth, breast feeding |
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Horizontaltransmission |
is person to person via air, physicalcontact, ingestion of food or water, or vector |
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DirectContact |
–handshake, sexual intercourse •Infectious dose important (e.g., for Shigella is 10–100 cells, can happen fromhandshake)•From hands, can be ingested: fecal-oraltransmission •Handwashing considered single most important measurefor preventing spread of infectious disease |
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IndirectContact |
inanimate objects, or fomites •Clothing, table-tops, doorknobs, drinkingglases |
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Mechanismsof transmission (3) |
DropletTransmission Food and Water Air |
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DropletTransmission |
–respiratory droplets generally fall toground within a meter from release -Densely populated buildings (schools,military barracks) -Spread minimized by covering mouth whensneezing |
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Foodand Water |
–can become contaminated•Animal products (meat, eggs) fromanimal’s intestines•Cross-contamination: transfer from one food to another |
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Air: |
–: respiratory diseases commonlytransmitted•Particles larger than 10 µm usually trapped by mucus •Smaller particles can enter lungs, carrypathogens •Talking, laughing, singing, sneezing,coughing generate |
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Vectors |
–living organisms that can carry pathogen •Most commonly arthropods: mosquitoes,flies, fleas, lice, ticks; can carry internally or externally•Can be mechanical or biological •Vector control important in preventingdiseases |
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Onekey parameter in an epidemiology is |
•Ro |
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•Ro |
•Describeshow many infections will originate from one infected individual |
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Ro<1 |
infectionwill not spread |
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Ro>1 |
•infectionwill spread |
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Vaccines :•Basedon the principles of herd-immunity•Stopthe spread of infectious diseases from |
–individualsthat cannot be vaccinated –Immunocompromisedindividuals –Veryyoung children and the elderly |
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Inmodeling, vaccination tends to |
•reduceRo and will break links betweenpeople in a population |
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Colonization refers to |
microbe establishing itself on bodysurface |
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–Term infection can be used to refer to pathogen |
•Can be subclinical: no or mild symptoms •Infectiousdisease yields noticeable impairment–Symptoms are subjective effects experienced bypatient (e.g., pain and nausea) –Signs are objective evidence (e.g., rash, pusformation, swelling) •Initial infection is primaryinfection –Damage can predispose individual todeveloping a secondaryinfection |
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Primarypathogen |
–is microbe or virus that causes diseasein otherwise healthy individual •Diseases such as plague, malaria,measles, influenza, diphtheria, tetanus, tuberculosis, etc. |
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Opportunisticpathogen |
–(opportunist) causes disease only whenbody’s innate or adaptive defenses are compromised or when introduced intounusual location •Can be members of normal microbiotaor common in environment (e.g., Pseudomonas) |
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Virulence |
refers to degree of pathogenicity |
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Virulencefactors |
–are traits that allow microorganism tocause disease |
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Communicable or contagious diseases |
–easily spread |
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Infectiousdose is |
number of microbes necessary to establishinfection |
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ID50 is |
number of cells that infects 50% ofpopulation |
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Shigellosis results from |
~10–100 ingested Shigella |
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Salmonellosis results from |
many as 10^6 ingested Salmonella entericaserotype Enteritidis–Difference partially reflects ability tosurvive stomach acid• |
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Incubationperiod |
–time between infection and onset •Varies considerably: few days for commoncold to even years for leprosy Depends on growth rate, host’s condition,infectious dose |
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Illness: |
–signs and symptoms of disease May be preceded by prodromal phase (vague symptoms) |
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Convalescence |
recuperation, recovery from disease |
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Carriers |
–may harbor and spread infectiousagent for longperiods of time inabsence of signs or symptoms |
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Localizedinfection |
–microbe limited to small area (e.g., boilcaused by Staphylococcus aureus) |
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Systemicinfection |
–agent disseminated throughout body (e.g.,measles) |
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Suffix -emiameans |
–in the blood” |
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Bacteremia |
•bacteria circulating in blood –Not necessarily a disease state (e.g.,can occur transiently following vigorous tooth brushing |
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Toxemia |
toxins circulating in bloodstream |
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Viremia |
viruses circulating in bloodstream |
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Septicemia or sepsis |
acute, life-threatening illness caused byinfectious agents or products in bloodstream |
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•Pathogenesis•Several general patterns–Produce toxins that are ingested |
E.g., Clostridiumbotulinum, Staphylococcusaureus |
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–Colonize mucous membranes, produce toxins |
•E.g., Vibriocholerae, E.coli O157:H7, Corynebacterium diphtheriae |
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–Invade host tissues, avoid defenses |
–E.g., Mycobacteriumtuberculosis, Yersiniapestis, Salmonellaenterica |
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–Invade host tissues, produce toxins |
•E.g., Shigella dysenteriae,Clostridium tetani• |