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103 Cards in this Set
- Front
- Back
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Four outcomes of microorganism introduction to the body
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Transient; pass through
Colonize to become part of normal flora Establish infection Cause disease |
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Pathogenicity
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Ability of an organism to cause disease
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Pathogen
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Bacterium that can harm a normal host
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Opportunistic pathogen
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Harms a compromised host
ex. pseudomonas aeruginosa |
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Virulence
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# of bacteria needed to cause disease; determines extend of disease
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Virulent organism
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Causes disease in most individuals
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Avirulent organism
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Rarely, if ever causes disease in human beings
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Virulence factors
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Allow entrance to the host, colonization, resistance of immune defenses, causing damage
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Primary infection
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Initial, acute infection
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Secondary infection
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Later infection by opportunistic bacteria, after host defences are weakened by a primary infection
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Subclinical infection
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Has no apparent symptoms
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Nosocomial infection
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Acquired as a consequence of hospitalization
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Local infection
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Restricted to a small area of the body, typically caused by non-invasive organisms
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Systemic infection
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Spread throughout the body, typically caused by invasive organisms
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Focal infection
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Begins in a restricted area, spreads throughout the body
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Invasiveness of an organism
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Ability of the organism to invade beyond the original site of entry
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7 factors that can increase susceptibility
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Underlying disease
Stress Poor nutrition Age Immunosuppressive therapy Genetics Normal flora |
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Normal flora
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Colonize human body surfaces without causing disease
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Normal flora benefit by:
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Nutrient supply
Stable environment Mode of transport |
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Host benefits from normal flora
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Microbial antagonism, nutritional synergisms
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Harmful aspects of normal flora
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Pathogenic potential, production of intestinal gas
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Normal flora outcompete pathogens by (4)
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Occupying adherence sites
Utilizing nutrients Producing inhibitory byproducts Affecting pH |
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Normal flora help the host by (4)
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Producing excess Vitamin K, B12
Steroid metabolism Producing organic acids Glycosidase reactions |
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Hygiene hypothesis
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Kids aren't exposed to enough microorganisms; exposure later in life can result in allergies
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Factors affecting normal flora composition (3)
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Diet, infection, antibiotic therapy
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Plaque
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(dental), is a complex biofilm
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Dental caries
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Destruction of enamel, caused by strep. mutans, lactic acid bacteria
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Periodontal diseases
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Inflammation of supporting structures of the teeth
ex. gingivitis - inflammation of the gums |
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Gastric ulcers
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Caused by H. pylori, normal flora of the stomach
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SCIO
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Severe combined immune deficiency, lacks B cells and T cells
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Biofilms
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Organized communities of bacteria adhered to a surface
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EPS
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Extracellular polymeric substances - slimy substance produced by bacteria for biofilm
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EPS can provide
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Structure, controlled environment, protection
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Quorum sensing
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Detects concentration of autoinducers -> bacterial concentration to encourage biofilm formation
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Planktonic cell
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Single bacterial cell growing in liquid
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Benign biofilms
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Slipper coatings on rocks, etc. can cause industrial problems, but not usually associated with disease
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Pathogenic biofilms
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Can cause human infection and disease
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Biofilm formation process (3)
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Adherence
Growth, EPS production Dispersion of single cells |
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Pseudomonas aeruginosa
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Causes cystic fibrosis
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Persister cells
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Antimicrobial treatments may leave behind a few cells because of EPS presence -> can regrow into a new colony
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Lactoperoxidase
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Generates a toxic, singlet oxygen
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Lactoferrin
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Binds iron
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Lysozyme
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Cleaves glycosidic bonds in peptidoglycan, destroying the cell wall
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Antimicrobial peptides
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ex. beta defensins, LL-37
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Antiseptics
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Chemical agents applied to living tissues to kill or inhibit microorganism growth
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Disinfectants
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Chemical agents used on inanimate objects to kill microorganisms (too toxic to be used inside the body)
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Chemotherapeutic agents
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Can kill or inhibit bacteria without causing serious harm to the host, ex. antibiotics
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Broad-spectrum antibiotics
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Act on gram-positive and gram-negative bacteria, common
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Narrow spectrum antibiotic
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Acts only on a single group of organisms
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MDR pathogen
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Multi-drug resistant pathogen, develops due to abuse of antibiotics
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Active immunization
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Inject the vaccine into humans to induce an antibody response
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Passive immunization
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Inject preformed antibodies into an infected person
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General purpose media
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Used for growth of most bacteria
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Enriched media
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Used for growth of metabolically intensive bacteria, with specific growth factors
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Selective media
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Has compounds that inhibit the growth of certain bacteria
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Differential media
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Indicator dye allows identification of bacteria based on appearance
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Zone of inhibition is dependent on (3)
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Degree of sensitivity, growth rate of bacterium, diffusion rate of antibiotic
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Agglutination assays
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Recognize antigen group
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Fluorescently labelled antibodies
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Recognize surface antigens
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Serological assays
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Growth-independent measures
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Epidemiology
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Where and when diseases occur and how they are spread
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Incidence of disease
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Fraction of population that acquires the disease during a time period
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Prevalence of disease
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Fraction of a population with symptoms during a time period, including established cases
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Sporadic disease
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Occurs occasionally, recorded as individual cases in separate areas (not related)
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Endemic disease
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Occurs continually at a low level; may be due to a weak pathogen or population immunity
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Epidemic disease
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Occurs continually at a low level, but sporadically at an elevated level
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Pandemic disease
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Widely distributed epidemic
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Disease outbreak
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Number of disease cases in an area increases when there were only sporadic cases previously
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Reservoirs
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Sites in which viable infectious agents remain
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Symptomatic reservoir
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Currently have a disease
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Convalescent reservoir
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Human recovering from the disease but still harboring the infectious agent
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Carriers
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Have no disease symptoms, but carry the pathogen
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Acute carrier
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Carrier state is transient, ex. human was never sick but carries the disease
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Chronic carriers
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Individuals that have recovered from the disease, but still have the infectious agent (or have it in their normal flora)
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Zoonoses
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Diseases that occur primarily in animals but can be transmitted to humans
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Contact transmission
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Direct human contact
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Common vehicle transmission
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Transmission by inanimate objects, ex. food, water, blood, drugs
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Airborne transmission
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Transmission by droplets, dust ex. respiratory pathogens
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Vector transmission
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Transmission by living agents, ex. insects, ticks, mites, fleas, rodents; often skin or blood-borne
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Infectious dose
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Number of bacteria required to produce disease
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Lethal dose
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Number of bacteria required to kill
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Endogenous infection
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Caused by normal flora
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Exogenous infection
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Transmitted from another individual
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Iatrogenic infection
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Results from surgery, invasive diagnostic procedures, medical implant devices
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Bacteremia
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Bacteria presence in the blood
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Septicemia
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Evidence that bacteria is multiplying in the blood; can trigger a fatal immune response
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Bacterial adhesion is mediated by
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Receptor on host surface membrane, adhesin on bacterial surface
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Example of host receptor
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Glycoproteins, glycolipids
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Examples of bacterial adhesin
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Pili, capsule
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Toxins
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Microbia products that can damage the host
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Exotoxins
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Secreted proteins; heat labile, immunogenic
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Cytolytic toxins
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Attack cell constituents, causing lysis
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Neurotoxins
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Interfere with nerve cell function
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Enterotoxins
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Affect lining of the GI tract, causing diarrhea
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Toxoid
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Toxins treated with heat or chemicals to eliminate toxicity to the patient, but can still stimulate an immune response
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Endotoxins
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Produced when a bacteria dies or is digested; typically related to LPS (or LTA); non-protein; non-immunogenic
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Endotoxin shock
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Results from high dose of endotoxin: circulatory system damage, fluids leak out, blood coagulates, organs can fail
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Facultative pathogens
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Live within or outside cells
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Obligate pathogens
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Can only live within cells
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Bioterrorism
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Use of biological agents to cause damage, death or fear
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Serotype
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Classification of a bacteria by serovar
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Biovar
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Strains that are differentiated by biochemical or non-serological means
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Serovar
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Strain of bacteria differentiated by serological means
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