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78 Cards in this Set
- Front
- Back
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Symbiosis |
Relationship between 2 organisms |
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Holobiont |
Human plus all the microbiota (microbiome) |
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Mutualism |
Both members benefit |
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Commensalism |
Commensal benefits and other is unharmed |
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Parasitism |
Parasite is dependent and benefits while the other is harmed |
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Goal of human microbiome project |
- To characterize the relationship between the human body and microbes - To determine how the microbiome differs in various diseases |
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Findings of human microbiome project |
- Some microbial proteins are enzymes that help us digest our foods - We have microbes and locations that were thought to be sterile like the lungs - Viruses are resident on the human body and large quantities and all do not cause illness - All healthy people contain pathogens in low numbers but the normal microbiota protect us - Gut microbiome can influence many aspects of the human health (heart disease, asthma, autism, diabetes, moods) |
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Function and role of normal microbiota |
- Prevent growth of pathogens and aid in digestion - Produce growth factors such as folic acid and vitamin K |
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How is normal microbiota acquired |
- In utero: womb has its own microbiota - Birth: vaginal/c-section deliveries contribute different initial microbiomes to baby - Milk: breast milk/formula have differing microbes in them - Caregivers: family, siblings, and others share microbes with baby - Environment: baby can pick up microbes from anything it comes in contact with |
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Pathogen |
Disease causing agent |
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Infection |
Growth of microbes on host |
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Host |
Where pathogen lives |
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Transient microbes |
Microbes acquired in our environment that have the potential to cause disease (removed easily by handwashing) |
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Opportunistic pathogens |
Microbes that only cause disease when their host is weakened |
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Disease |
Deviation from normal health that results when infection disrupts normal function of the body |
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Portals of entry and examples |
How pathogens gain entrance to human body Ex: skin, GI tract, respiratory tract, urogenital tract, endogenous biota |
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Pathogenicity |
Ability of a microbe to cause disease |
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Virulence |
Degree of pathogenicity |
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Virulence factors and examples |
Ways pathogens overcome our defenses (toxins, harmful enzymes, capsules, adhesins) |
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How microbes enter the human body and examples |
- Respiratory tract: microbes inhaled (Influenza virus) - GI tract: microbes enter by food, water, contaminated objects (Hepatitis A) - Urogenital tract: commonly sexually transmitted (Herpes, HIV) - Skin: through injured skin, sweat glands, hair follicles(Hepatitis B, Rabies virus) |
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Parenteral route and example |
When microbes enter injured skin or mucous membranes Ex. Injections, bites, cuts, surgery, burns, etc |
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Preferred portal of entry and example |
Many pathogens have a preferred portal of entry in order to cause disease; if access is gained by another portal, disease may not occur Ex. Clostridium tetani must enter through punctured skin to cause disease |
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ID50 |
Infectious dose Dose required to cause infection in 50% of test animals |
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LD50 |
Lethal dose Dose required to kill 50% of test animals |
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Adherence of bacteria |
Adhesins/ligands: bind to receptors on host cells (glycocalyx, fimbriae) Biofilms: microbes form communities Capsules Surface proteins Viral spikes |
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Evasive host defense mechanisms |
- Capsule - M proteins - Mycolic acid - Leukocidins - Collagenases - Hemolysins - Coagulases - Hyaluronidase |
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Capsule (evasive host defense mechanism) |
Glycocalyx around cell wall prevents phagocytosis Microbe: bacillus anthrasis, streptococcus pneumoniae |
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M proteins (evasive host defense mechanism) |
Heat/acid resistant protein found in some microbe that helps attach microbe to host/prevent phagocytosis Microbe: streptococcus pyogenes |
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Mycolic acid (evasive host defense mechanism) |
Waxy lipid found on certain genera that prevent phagocytosis Microbe: mycobacterium tuberculosis |
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Leukocidins (evasive host defense mechanism) |
Damage/kill leukocytes Microbe: staphylococcus, clostridium difficle |
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Collagenases (evasive host defense mechanism) |
Breaks down collagen Microbe: clostridium perfringes |
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Hemolysins (evasive host defense mechanism) |
Kill/damage erythrocytes by forming protein channels in cell membranes (alpha, beta, gamma) Microbes: S. mitis, S. pyogenes, S. epidermis |
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Coagulases (evasive host defense mechanism) |
Coagulates (clots) fibrin in the blood Microbe: staphylococcus aureus |
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Hyaluronidase (evasive host defense mechanism) |
Digests hyaluronic acid (holds cells together) Microbe: group A streptococci (necrotizing fascitis) |
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How do bacteria cause damage to host cells |
Use hosts nutrients Direct damage (lysis) Toxins (poisonous substance) Induce hypersensitivity reactions |
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Toxigenicity |
Ability to produce toxins |
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Toxin |
Poisonous substance |
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Toxemia |
Presence of toxins in blood |
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Antitoxin |
Antibodies produced by host against specific toxins |
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Toxoid |
Altered (inactivated) exotoxin that can be injected as a vaccine |
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Exotoxins |
Toxin released directly into bloodstream, made of protein, mainly in Gram + bacteria |
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A-B toxins (exotoxin) |
Most common A - active enzyme portion B - binding portion Ex. Clostridium botulinum/tetani |
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Membrane disrupting toxin (exotoxin) |
Cause lysing of host cells by disrupting cell membrane (leukocidins, hemolysins) Ex. Clostridium perfeinges/difficle |
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Superantigen (exotoxin) |
Antigens that provoke an intense immune response and signal T cell production Ex. Staphylococcus aureus |
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Neurotoxin (exotoxin) |
Attack nerve cells Ex. Clostridium tetani |
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Enterotoxin (exotoxin) |
Affects GI tract Ex. Staphylococcus aureus |
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Cytotoxin (exotoxin) |
Lysis of host cells Ex. Clostridium perfringes |
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Endotoxins vs. Exotoxins |
Endo: - toxin in lipid part of LPS of cell wall and released when cell wall is damaged - only gram - produce them - all produce same symptoms in varying degrees Exo: - released directly into bloodstream - mainly in gram + bacteria - produce specific disease symptoms |
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Localized infection and example |
Microbe confined to a specific tissue Ex. Warts, boils, skin infections |
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Systemic infection and example |
Spread throughout bloodstream to a variety of body systems Ex. Measles, chickenpox, anthrax |
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Latent infection and example |
Host doesn't have any signs or symptoms Ex. Nonactive herpes |
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Acute infection and example |
Rapid onset and progression Ex. Influenze virus |
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Chronic infection and example |
Slower onset of symptoms Ex. Mononucleosis, HIV |
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Signs |
Can be measured (objective) Ex. Fever, swelling, rash, vomiting |
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Symptoms |
Cannot be measured (subjective) Ex. Pain, nausea, fatigue |
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Stages of infection and disease |
1. Incubation phase: initial contact to first symptoms 2. Prodromal stage: onset of symptoms 3. Acute phase: height of infection 4. Convalescent period: decline in symptoms, strength returns, may still be contagious |
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Epidemiology |
Studies patterns in disease incidence and control/prevention Uses Kochs postulates |
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Etiological agent |
Causative agent of an infectious disease |
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Kochs postulates |
1. Same organisms must be present in every case of disease 2. Organism must be isolated from diseases host and grown as a pure culture 3. Isolated organism should cause disease in question when introduced to a susceptible host 4. Organism must be resonated from inoculated/diseased animal |
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Reservoir of infection and example |
animate/inanimate habitat where the pathogen is normally found Ex. Human, animal, soil, water |
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Source and example |
Individual or object from which infection is actually acquired (more specific than reservoir) Ex. Unsafe water or food, saliva, sputum |
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Mode of transmission and example |
How disease is transferred Ex. Vertical (parent to offspring), horizontal (person to person) |
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Types of reservoirs |
Animals: bats and rabies Human: actively ill (indirect/direct transmission), carriers Arthropods: mosquitoes, fleas, ticks |
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Zoonotic and example |
Spread of disease from animals to humans Ex. Malaria and mosquitoes |
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Vector and example |
Live animal that transmits an infectious agent from one host to another Ex. Fleas, mosquitoes, ticks, flies, birds |
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Nonliving reservoir |
Soil (clostridium tetani/botulium) Fomites |
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Fomite |
Inanimate objects that transmit microbes |
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Noncommunicable and example |
Not spread from one person to another Ex. Clostridium tetani and tetanus |
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Communicable and example |
Microbe transmitted from human to human Ex. Influenza, common cold |
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Contagious and example |
Communicable disease easily transmitted from one human to another Ex. Measles, influenza, COVID19 |
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Asymptomatic carriers |
Can transmit pathogen but does not have any symptoms of disease Ex. Typhoid Mary |
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Direct contact transmission |
Person to person: saliva, touching, sex Animal: bite, touching Environment: swimming, soil Vertical: in utero, vaginally delivery, breast milk |
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Indirect contact transmission |
Airborne: respiratory aerosols, windborne, stirred up animal droppings Vehicle: foodborne, contaminated water/needles Biological vector: mosquito/tick/flea bite Mechanical vector: flies, cockroaches |
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Endemic and example |
Constantly present in a population or region with relatively low spread Ex. Malaria |
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Pandemic and example |
Sudden increase in cases across several countries, continents, or the world Ex. COVID 19 |
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Sporadic and example |
Occurring at irregular intervals or only in a few places Ex. Tetanus, E. coli, salmonella |
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Dr. Ignaz Semmelweis |
Linked handwashing to prevention of disease |
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Healthcare associated infections (nosocomial) and their transmission, diseases, prevention |
Disease that develops from Healthcare worker/environment Transmission: fomites, hospital personnel Diseases: clostridium difficle, UTI's, MRSA Prevention: handwashing, gloves, mask, gowns |
