Test Answers on Exam 3 – Microbiology – Flashcards
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| Mutualism- |
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| When both the host and organism benefit from the relationship i.e. bacteria in human colon |
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| Parasitism- |
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| When the organism benefits from the relationship and the host is harmed i.e. tuberculosis bacteria in the human lung |
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| Commensalism- |
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| When the host is not affected by the relationship and the organism is benefited i.e. Staphyloccus on skin |
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| Pathogenicity- |
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| Ability of a pathogen to cause disease in an organism |
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| Virulence- |
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| Describes the particular attributes of a specific microbe (species or strain) that promote pathogenicity; virulence can be a quantifiable term (avirulent, mildly virulent, and highly virulent). Virulence depends on virulence factors |
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| Describe the term “normal microbiota” |
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| Normal microbiota refers to the organism that colonizes the body’s surfaces without normally causing disease. In-utero, the fetus is free of normal flora in normal circumstances; the process of being colonized (establishment of microbial growth) with normal flora typically begins during the birthing process: MO of the GI tract MO of the skin MO of the genitourinary tract. Other forms of normal flora are acquired throughout the early years of life via environmental exposure: Food that we eat Person-to-person contact Environmental/airborne organisms |
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| Describe the terms resident and transient microbiota |
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| Resident microbiota permanently colonizes the host and is established during the first months of life. Transient microbiota colonizes the host for a short period of time and do not persist in the body due to the host’s defenses. |
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| List the areas on/in the human body that have normal microbiota and those areas that are axenic (considered to be sterile). |
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| Normal microbiota Eyes and skin Upper respiratory tract Upper digestive tract Lower digestive tract Female/male urinary and reproductive systems Axenic (sterile) Body fluids (CSF), organs and blood |
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| Describe probiotics and the benefits of having normal flora |
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| Probiotics are live microbes applied to or ingested into the body that intend to exert a beneficial effect. Normal flora provide dietary nutrients (e.g. vitamin k, B-12) Bacterial antagonism: (normal vs. normal and normal vs. transient): -Nutrient competition |
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| Describe three conditions that create opportunities for normal microbiota to become an opportunistic pathogen. |
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| 1. Immune suppression 2. Changes in the normal microbiota (changes in relative abundance of normal microbiota may allow opportunity for a member to thrive and cause disease) 3. Introduction of normal microbiota into sterile area of body (axenic environment) |
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| Contamination- |
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| Presence of microbes in or on the body |
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| Infection- |
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| Results when the organism has evaded the body’s external defenses, multiplied and become established in the body |
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| Disease- |
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| Results only if the invading pathogen alters the normal functions of the body; disease is also referred to as morbidity |
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| Describe the four portals of entry through which pathogens invade the body. |
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| Skin- Via openings or cuts, burrowing into or digesting the outer layers of skin Mucous membranes- Exposure to environment Parenteral route- Requires direct deposit onto tissues by punctures, cuts, bites, stab wounds, deep abrasions or surgery Placenta- From mother to fetus |
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| Discuss how the virulence factors help microbes establish disease in humans. |
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| Adhesion factors- Structures or proteins used for attachment of pathogen to host cell Biofilms- Community of glycocalyx attached to a surface within the host, they are extremely resistant to host defenses Extracellular enzymes- Enzymes secreted by the pathogen, dissolve structural chemical in the body and help the pathogen maintain infection, invade further and avoid body defenses Toxins- Chemicals that harm tissues or trigger host immune responses that cause damage. Antiphagocytic factors- Certain factors prevent phagocytosis by the host’s phagocytic cells Bacterial capsule is often composed of chemicals found in the body and not recognized as forgein Antiphagocytic chemicals some prevent fusion of lysosome and phagocytic vesicles and leukocidins directly destroy phagocytic white blood cells |
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| Differentiate between bacterial exotoxins and endotoxins. |
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| Exotoxins destroy host cells or interfere with host metabolism Endotoxins are released when bacteria dies (Lipid A) |
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| Differentiate between a sign, symptom and syndrome |
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| SIGN- Objective manifestations of disease that can be observed or measured by others SYMPTOM- Subjective characteristics of disease felt only by the patient SYNDROME- Group of symptoms and signs that characterize a disease or abnormal condition |
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| Describe the five stages of infectious diseases. |
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| Incubation period- No signs or symptoms Prodromal period- Vague general symptoms Illness- Most severe signs and symptoms Decline- Declining signs and symptoms Convalescence- No signs of symptoms |
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| Describe the reservoirs of infection and give an example of a disease that humans acquire from that reservoir. |
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| Reservoirs of infection- Continual source of infection where pathogens can persist and maintain their ability to infect. AIDS, gonorrhea, typhoid fever are asymptomatic infections or latent diseases that are reservoir infections. |
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| Explain how microbes are transmitted from one host to another via contact transmission. |
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| Contact transmission Direct contact e.g. handshaking, kissing, sexual intercourse, insect bites Indirect contact e.g. drinking glasses, toothbrushes, toys, punctures Droplet transmission e.g. droplets from sneezing (within 1 meter) |
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| Explain how microbes are transmitted from one host to another via vehicle transmission. |
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| Vehicle transmission Airborne e.g. dust particles Waterborne e.g. streams and swimming pools Foodborn poultry, sea food, meat |
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| Explain how microbes are transmitted from one host to another via vector transmission. |
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| Vector transmission Mechanical e.g. insect bodies (fleas, roaches) Biological e.g. lice, mites, mosquitoes and ticks |
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| Distinguish between the following terms used to classify infectious diseases. Acute vs chronic |
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| Acute- Disease in which symptoms develop rapidly and that run its course quickly Chronic- Disease with usually mild symptoms that develop slowly and last a long time |
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| Distinguish between the following terms used to classify infectious diseases Communicable vs contagious vs noncommunicable |
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| Communicable disease- Disease transmitted from one host to another Contagious disease- Communicable disease that is easily spread Noncommunicable disease- Disease arising from outside of hosts or from opportunistic pathogen |
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| Epidemiology- |
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| The study of where and when disease occurs and how they are transmitted in a population |
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| Incidence vs prevalence- |
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| Incidence- Number of new cases of a disease in a given area during a period of time Prevalence- Number of total cases of a disease in a given period of time |
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| Endemic vs epidemic vs pandemic |
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| Endemic- Disease that is constantly present in a population in a geographic location but numbers/severity is too low to pose threat Epidemic- Disease acquired by many hosts in a given area in a short time (higher than normal incidence) Pandemic- Worldwide epidemic |
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| Etiologic agent- |
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| Cause of disease |
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| Morbidity vs mortality |
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| Morbidity- Incidence of a specific notable disease, number of people affected/total population in a given time period Mortality- Deaths from notable disease, number of disease/total population in a given time |
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| Define three types (sources) of nosocomial infections and explain how health care workers can decrease the risk of these infections in patients. |
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| Exogenous- Pathogen acquired from the health care environment Endogenous- Pathogens arise from normal microbiota due to factors within the health care setting Latrogenic- Results from modern medical procedures |
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| 17. Describe three factors that influence the development of nosocomial infections. |
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| Presence of microorganisms in the hospital environment Immunocompromised patients Transmission of pathogens between staff and patient and among patients |
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| 1. Explain the difference between fungi and bacteria in regard to cell type, cell wall composition, spore production and sensitivity to antibiotics. |
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| Fungi Cell type: Eukaryotic Cell wall composition: Sterols present Spore production: Produce a wide variety of sexual and coexual reproductive spores Sensitivity to antibiotics: Often sensitive to polyenes, imdazoles and griseofulvin Bacteria Cell type: Prokaryotic Cell wall composition: Peptidoglycan Spore production: Endospores (not for reproduction) and some asexual reproductive spores Sensitivity to antibiotics: Often sensitive to penicillins, tetracyclines and aminoglycosides |
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| Discuss the optimal growth temperature, cellular and colonial morphology of yeast and molds |
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| Yeast Optimal growth temperature 37 C Cellular morphology Unicellular Colonial morphology Oval, white colonies Mold Optimal growth temperature 25 C Cellular morphology Multicellular Colonial morphology Both vegetative and aerial hyphae |
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| Differentiate between aerial and vegetative hyphae. |
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| Aerial hyphae Hyphae that is above the nutrient surface Vegetative hyphae Hyphae that is below the nutrient surface |
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| Define “dimorphism” and list the five dimorphic fungi that cause disease in humans |
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| Dimorphic: Are yeast at 37 C (in the body) and mold at 25 C (in nature) Sporothrix schenkii causes rose thorn disease or gardener’s disease Coccidioidomycosis San Joaquin valley fever Histoplasmosis Ohio valley fever Blastomycosis Chicago disease or North American Blastomycosis Paracoccidiodomycosis South American Blastomycosis |
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| Classify fungus by their sexual means of sporulation (produce aerial hyphae). |
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| Zygomycete: produce zygospores i.e. Rhizopus (bread mold) Ascomycete: produce ascospores i.e. penicillium, saccharomyces Basidiomycte: produce basidiospores i.e. mushrooms, crytococcus Deuteromycete: reclassified using DNA technology i.e. stachybotrys, pneumocystis |
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| Recognize the asexual spores produced by fungus (used to classify in clinical lab). |
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| Sporangiospores: form in sac called sporangium Conidiospores: no sac, form at tip or side of hyphae Chlamydospore: thickened cell wall inside hyphae |
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| Name the classification of fungal diseases based on the location in the body. |
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| Systemic mycoses: Deep within the body Subcutaneous mycoses: Beneath the skin Cutaneous mycoses: Affect hair, skin and nails Skuperficial mycoses: Localized on the outermost skin layers/hair shafts Opportunistic mycoses: Caused by normal microbiota or fungi that is normally nonpathogenic |
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| Discuss the causative agent (name of the fungus that causes the disease), geographic location, and route of transmission of the following diseases Coccidioidomycosis (San Joaquin Valley fever) |
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| Name of fungus: Coccidioidomycosis immitis Geographic location: Thrives in areas with sandy alkaline soils, very high temperatures, Low rainfall, and low elevation Route of transmission Airborne arthrospore is inhaled |
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| Discuss the causative agent (name of the fungus that causes the disease), geographic location, and route of transmission of the following diseases: Histoplasmosis (Ohio Valley fever) |
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| Name of fungus: Histoplasmosis capsulatum Geographic location: Mostly in eastern United States but also in Africa and Asia Route of transmission: Inhalation of spores into the lungs |
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| Discuss the causative agent (name of the fungus that causes the disease), geographic location, and route of transmission of the following diseases: Blastomycosis (Chicago disease, North American Blastomycosis) |
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| Name of fungus: Blastomycosis dermatitidis Geographic location: Southeastern United States north to Canada Route of transmission Inhalation of dust can carry fungal spores or hyphal pieces into the lungs |
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| Discuss the causative agent (name of the fungus that causes the disease), geographic location, and route of transmission of the following diseases: Paracoccidioidomycosis (South American Blastomycosis) |
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| Name of fungus: Paracoccidioidomycosis brasiliensis Geographic location: Southern Mexico and South America Route of transmission Inhalation of sprores |
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| Recognize the three fungi that are dermatophytes |
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| Trichophyton Epidermophyton Microsporum |
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| Discuss the causative agent and characteristics of the following fungal infections: Cryptococcal meningitis |
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| Most common clinical form of cryptococcal infections Follows dissemination of the fungus to the CNS Symptoms include headache, stiff neck, nausea, photophobia, hallucinations, and fever |
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| Discuss the causative agent and characteristics of the following fungal infections: Rose thorn (Gardener's) disease- Sporotrichosis |
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| A subcutaneous infection that is usually limited to the arms and legs Individuals who work with natural plant material are at highest risk for infection Symptoms include nodular lesions around the infection site and secondary lesions can occur on the skin along the course of lymphatic vessels |
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| Discuss the causative agent and characteristics of the following fungal infections Ringworm (Dermatophytosis) |
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| Fungal infections of the skin, hair, nails Result from fungi that use keratin as a nutrient source and thus colonize only dead tissues Symptoms include a skin lesions that resembles a worm lying below the surface of the skin Can provoke cell mediated immune response that damages living tissues |
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| Discuss the causative agent and characteristics of the following fungal infections: Candidiasis (Thrush, Vaginitis, Diaper rash, Onychomycosis) |
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| Most common causative agent Normal flora of skin and mucous membrane can be transmitted between individuals always an opportunist infection that produces a wide rage of diseases |
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| Mycetismus: |
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| Mushroom poising from eating a fungus |
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| Mycetoma |
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| A chronic, slowly progressing fungal infection usually of the foot or leg, characterized by nodules that discharge oily pus |
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| Mycotoxicosis |
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| Caused by eating foods contaminated with fungal toxins |
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| Mycotoxins: |
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| Normal byproducts of metabolic activities but are poisonous to animals and humans |
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| Name two mycotoxins produced by fungus |
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| Aflatoxins: Produced by Aspergillus flavus Ergot alkaloids: Used to make drugs that treat migraine headaches, constrict blood vessels and stimulates labor contractions |
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| Differentiate between bacteria and virus particles |
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| Viruses are much smaller than bacteria Viruses contain DNA or RNA bacteria contain DNA Viruses are acellular particles and bacteria are living organisms Viruses are not susceptible to antibiotics bacteria are susceptible to antibiotics |
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| Describe the parts of a viral particle and their purpose: |
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| Genome Either RNA or DNA (never both) either single or double stranded usually circular but may be linear Capsid Protein coat composed of repeating protein subunits (capsomeres) provide protection and attachment sites the viral caspid determines the viral shape (helical, lcoshaderial, or compelx) Envelope Acquired from host cell during viral replication or release envelope is a portion of membrane system of host composed of phospholipid bilayer some proteins are virally-coded glycoproteins (spikes) envelopes proteins and glycoproteins often play a role in host recognition Virion A viruses extracellular state, a viral particle that is infectious and ready to attack |
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| Host range |
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| The type of host that it can infect, most viruses can only infect particular kinds of host cells, due to affinity of viral surface proteins/glycoproteins for complementary proteins/glycoproteins on host cell |
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| Tissue tropism |
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| The cell type or tissue within a host cell that it can infect (HIV infects T helper WBC, Rabies infects nervous tissue) |
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| Burst time |
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| The time from when a virus enters cells to when it is released |
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| Burst size |
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| Number of viruses produced and released, depends on the type of virus and size and initial health of host cell |
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| Latency |
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| When animal viruses remain dormant in host cells, may be prolonged for years with no viral activity, signs or symptoms. |
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| Provirus |
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| When a latent virus is incorporated into host DNA and becomes a permanent part of the hosts chromosome |
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| Naked virus |
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| A virus that has a capsid and a nucleic acids (no envelope) |
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| Differentiate between bacteriophage lytic and lysogenic cycles. |
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| Lytic cycle Replication cycle usually results in death and lysis of host cell Lysogenic cycle Replication cycle may include viral nucleic acid incorporated into host DNA (prophage) |
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| Describe the six steps of animal virus replication |
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| Attachment Chemical attraction, animal viruses don’t have tails or tail fibers they have glycoprotein spikes or other attachment molecules that attach to cell membrane Entry Whole viral particle enters the cell Uncoating Caspid is degraded Synthesis Production of nucleic acids and proteins Assembly Nucleic acids and caspid proteins assemble Release By budding or rupture |
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| Plaque formation (phage typing) |
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| The culturing of bacteriophage in bacteria, the virus infects the bacteria, the bacteria are lysed, die and show up as clear areas on the media |
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| Cytopathic effect |
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| When a cell looks sick, when you can visually see the infected cell in the lab |
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| Inclusion bodies |
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| Visible evidence that cells are infected with a virus, produce an inclusion within the infected cell |
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| Cell culture |
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| Monolayer of cells with nutrients for cells, the cells are the bacteria (media) that the virus infect |
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| Serologic tests |
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| Use antibodies to identify viruses, it detects patient antibodies against viruses |
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| Describe how interferon and antiviral drugs are able to inhibit viral replication |
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| Antiviral drugs Prevent attachment Nucleotide base analogs (look like A,T,C,G U but don’t act the same way) Reverse trancriptase inhibitors Protease inhibitors Neuraminidase inhibitors (H1N1 virus) Interferon Proteins produced by an infected cell that signals a non-infected cells to begin producing antiviral proteins |
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| Differentiate between inactivated, attenuated and subunit vaccines |
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| Inactivated “Killed” virus by heat or chemical Attenuated “Weakened” virus Subunit Protein molecules produced by genetic engineering |
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| Virods |
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| Tiny fragments of RNA without a capsid; cause disease in plants |
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| Prions |
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| Proteins without nucleic acids, inherited and transmissible by ingestion, transplant, and surgical instruments |
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| Describe how prions “replicate”. |
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| Prions "replicate" by changing the structure of the already existing cellular PrP (normal) into the (abnormal)prion PrP |
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| Name the disease caused by prions. |
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| Spongiform encephalopathies |
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| State the method needed to inactivate a prion. |
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| Only destroyed by incineration or autoclaving in 1NaOH |
