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216 Cards in this Set
- Front
- Back
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COMULATIVE |
COMULATIVE |
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D |
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S |
S |
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where are viruses found? |
in or on every material and environment on earth; anywhere there are cells to infect |
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Viruses contain either ___ or ___ but not both |
RNA; DNA |
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Size of viruses |
ultramicroscopic in size, ranging from 20 nm up to450 nm (diameter). |
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Are viruses cells? |
They are not cells; structure is very compact and economical. |
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Viruses are ___ macromolecules outside the host cell and ___ only inside the host cells |
inactive; active |
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Basic structure of a virus consists of _____ surrounding_____ core. |
protein shell (capsid); nucleic acid |
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What type of nucleic acid do viruses have? |
Either DNA or RNA but not both |
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How do viruses attach to host cells? |
Molecules on virus surface impart high specificity forattachment to host cell |
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How do viruses multiply? |
by taking control of host cell’s genetic material andregulating the synthesis and assembly of new viruses. |
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Why can't viruses perform most metabolic processes? |
Lack enzymes |
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Why can't viruses synthesize proteins? |
Lack machinery |
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Viruses are ___ ____ rather than organisms |
infectious particles |
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Viruses are ___ or ___ rather than alive or dead |
active; inactive |
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Virus size compared to bacteria |
smaller than most bacteria |
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What microscope is needed to see viruses? |
Electron microscope |
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Size of parvovirus |
20nm wide |
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Mimiviruses size |
450nm long; larger than some small bacteria |
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Cylindrical virus size
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Mimi virus 450 nm
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capsid together with nucleic acid |
nucleocapsid |
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Virus spikes |
Allow docking w/ host cell |
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Virus spikes found on |
naked and enveloped viruses |
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What is a virion? |
fully formed virus able to establish infection in a host |
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Capsomeres are |
identical protein subunits of capsid |
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How do capsomeres form? |
spontaneously self assemble |
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Icosahedral capsid: |
3D, 20-sided figure w/ 12 evenly spaced corners |
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Helical Capsid in enveloped viruses: |
usually a modified piece of host cell membrane (animal viruses only) |
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Complex Capsids |
found in bacteriophage Have multiple types of proteins Takes shapes that aren't symmetrical |
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Bacterio phage
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Infect bacteria |
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"T-even" bacteriophage |
infect E. Coli T-2 and T-4 are examples Most widely studied bacteriophage Go through similar stages as animal viruses |
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Envelope |
Composed of membrane system of host Cell membrane or nuclear membrane Regular membrane proteins are replaced with viral proteins Contains spikes made of glycoproteins |
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Viruses can be classified based on type of ___ ___ |
nucleic acid |
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Virus DNA can be ___ or ___ stranded |
single; double |
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Single stranded RNAPositive-sense RNA:
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Ready for immediate translation into proteins Reverse transcriptase viruses aka retroviruses |
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Single strandedNegative-sense RNA: |
Need to be converted to proper form to be made into proteins |
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Informal classification and Naming of viruses is based on: |
Host Nucleic acid type Shape |
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Formal classification and naming of viruses is based on: |
StructureChemical compositionsSimilarities in genetic makeup |
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Virus families: (ends in) |
Suffix -viridae |
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Virus genera: (ends in)*genera is plural of genus |
Suffix -virus |
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Multiplication Cycle in Animal Viruses |
1. Adsorption2. Penetration3. Uncoating4. Synthesis5. Assembly6. Release form host cell |
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Adsorption |
Invasion begins when virus encounters susceptible host and adsorbs specifically to receptor sites on cell membrane Receptor sites usually used for normal function such as communication Limited host range |
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Host Range |
Virus can invade its host cell only through making an exact fit with specific host molecule |
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Restricted host range example |
hepatitis B only infects liver cells of humans |
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Intermediate host range example |
poliovirus infects intestinal and nerve cells of primates |
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Broad host range example |
rabies virus infects various cells of all mammals |
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Penetration by Endocytosis |
Endocytosis: virus engulfed by cell and enclosed in vacuole or vesicle Uncoating: enzymes in the vacuole dissolve envelope and capsid, releasing virus into cytoplasm |
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Penetration by fusion |
Viral nucleic acid takes control of machinery of host's synthetic and metabolic machinery |
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RNA virus synthesis happens in
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Cytoplasm
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Release of Mature Viruses |
Viral budding or exocytosis: Nucleocapsid binds to membrane Small pouch is formed Pinching off of pouch releases virus w its envelope Viruses are shed gradually without destruction of cell |
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Cytopathic Effect types |
Inclusion bodiesSyncytia (singular, syncytium) |
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Inclusion bodies |
Compacted masses of viruses or damaged cell organelles in nucleus or cytoplasm |
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What are inclusion bodies |
Compacted masses of viruses that divide in a host cell and damages the hosts organelles |
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Persistent Infections
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A carrier relationship that develops in some cells Cell harbors virus and is not immediately lysed |
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Provirus |
retrovirus DNA incorporated into host DNA retrovirus DNA incorporated into host DNA
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Chronic. latent state
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periodic activation after period of viral inactivity
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Oncogenic virus |
cancer causing virus Experts estimate that 20% of human cancers are virus-caused |
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Types of Transformations |
Increased rate of growthAlterations in chromosomesChanges in cell's surface moleculesCapacity to divide for an indefinite period |
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Oncoviruses |
virus capable of initiating tumors |
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Cancer-causing viruses
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Papillomaviruses cervical cancer
Epstein-Barr virus hodgkn lymphoma mononucleosisOral transfer of saliva or genital secretions; lymphoma (HH-V6) human herpes virus lymphoma
HTLV-1: asymptomatic. Sexual transmission; lymphoma |
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How do viruses cause cancer? |
1. Carry genes that directly cause cancer DNA is incorporated into cell 2. Produce proteins that induce a loss of growth regulation in the cell DNA isn't incorporated into cell |
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How do viruses cause cancer |
1. carry genes that directly cause cancer (RNA attaching to animal DNA, RNA stim. oncogenes to turn on in host), 2. produce proteins that induce a loss of growth and regulation in a cell |
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Lysogenic cycle |
Bacteriophage becomes incorporated into host cell DNA |
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Lysogeny: the Silent Virus Infection |
Temperate phages: Have ability to undergo adsorption and penetration but do not immediately undergo replication or release |
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Induction |
activation of a prophage in lysogenic cell to undergo lytic cycle |
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Lysogeny in Human Diseases |
Some phage genes in the bac. chromosome cause production of toxins or enzymes that cause human pathology |
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Lysogenic conversion |
Acquisition of a new trait from temperate phage Responsible for cholera and botulism toxin |
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What is lysogenic conversion |
Acquisition of new traits from a temperate phase (is responsibe for cholera and botulism) |
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Poxviridae |
Small pox: 80% mortality Transmission by contact/inhalation Eradicated in 1977 |
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Cowpox |
causes pustules Can infect many animals Transmission by casual contact People that got this from touching cow udders (which gave temporary pustules on hands) never contracted smallpox |
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Herpesviridae |
Herpes simplex 1 (HSV-1)HSV-2HSV-3 Transmitted casually US: 9,000 hospitalization a; 100 deaths/yrComplicated cases can be treated |
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Herpes simplex 1 (HSV-1)
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Fever blisters cold sores transmission Saliva; usually during childhood |
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HSV-2 |
genital herpesTrasmitted sexually/skin contact |
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HSV-3 |
Varicella zoster virus (chickenpox, shingles) causes pustules |
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Papillomaviridae |
Human papillomavirus: warts, usually asymptomatic Infects skin or mucosal epithelium of the genitals, anus, mouth, or airways Enter keratinocyte stem cells through cutsHPV 16 and 18 can lead to cancer U.S.: >6,000 deaths/yr |
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Human Papillomavirus Vaccine |
Prevents infections by HPV types associated w/ cervical cancer, genital warts, and other cancers Highest efficacy when given to 11-12 year olds |
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Poliovirus (RNA virus) |
Causes polio: paralysis (1% of cases), virus enters CNS and replicates in motor neurons -> destruction of neurons Fecal-oral transmission Eradicated from Africa (26 October 2015). Now only in Pakistan/Afghanistan |
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Human Rhinovirus (RNA virus) |
Causes common cold: sore throat, runny noise, nasal congestion, etc. Spread by aerosols, contaminated surfaces, person-to-person contact Recent data suggests that dry air causes increased transmission and infection |
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Flavivirus (RNA virus) |
Dengue fever: headache, muscle/joint pains, skin rash. Dengue hemorrhagic fever: bleeding Both spread by mosquitos 500 million cases worldwide/yr, 25K deaths West Nile fever: 80% asymptomatic, flu-like to encephalitis Spread by mosquitos US: 1,500 cases in 2015 |
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Ebola (RNA virus) |
Causes hemorrhagic fever- fever and bleeding 50% progresses to high fever, shock, and death Transmission: casual contact 2014 Africa outbreak: 18,000 cases, 7,000 deaths Transmitted to humans from direct contact with or eating bats. |
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Rabies (RNA virus) |
Causes encephalitis Begin 1-3 months after infection; 100% fatal Transmission: infected animal bite or scratch (saliva): US: bats; developing countries: dogs US: 1-3 cases/yr |
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Measles (RNA virus)
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Double Stranded RNA Flu-like sometimes at first, then Koplik's spots (mouth) and red body rash Airborne transmission Causes most vaccine-preventable deaths of any disease; 100K/yr worldwide |
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HIV (RNA virus) |
Retrovirus Causes acquired immunodeficiency syndrome (AIDS): progressive failure of the immune system Transmitted sexually US: 1.2 million infected, 13,000 deaths/yr |
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Viruses and Human Health |
Impossible to measure infections worldwide Most common cause of acute infections w/o hospitalization: Colds, chickenpox, influenza, herpes, warts Some with high mortality rates: Rabies Ebola Other viral infections lead to long-term disability: Polio |
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Viruses and Vaccines |
Viruses mutate at rapid rate Difficult to design therapies against viruses Scientists focus on developing vaccines against viruses since so few antiviral drugs are available Antibiotics are ineffective |
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Noncellular Infectious Agents |
Prions Satellite viruses Viroids |
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Prions |
Proteinaceous infectious particles Contain no genetic materials Cause transmissible spongiform encephalopathies (TSE) |
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How prions work |
Normal proteins in brain (PRP^c) is transformed into a prion protein (PRP^sc) Altered protein spontaneously converts other PRP^c proteins into PRP^sc proteins Accumulation of PRP^sc proteins cause plaques and spongiform damage in the brain Can cause disease when transferred to a new host |
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How do prions spread? |
Contaminated instruments Infected meat |
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5 types of Transmissable Spongiform Encephalopathies (TSEs) |
Creutzfeldt-Jakob Disease (CJD) Fatal Familial Insomnia Scrapie Bovine Spongiform Encephalopathy Chronic Wasting Disease |
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Creutzfeldt-Jakob Disease (CJD) |
Affects CNS of humans Causes fast degeneration 90% death rate within 1 year Transmission: Unknown No treatment, no cure. |
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Fatal Familial Insomnia |
Causes progressively worsening insomnia, leading to hallucinations, delirium, and dementia 100% fatal within 6 months of first symptoms Not transmissible; inherited |
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Animal Prions |
Scrapie: sheep, goats Bovine spongiform encephalopathy: mad cow disease Can be transmitted to humans (vCJD), 225 human deaths Chronic wasting disease : elk, deer Might be transferred by eating them but we don't know for sure |
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Satellite viruses (not prions) |
Dependent on other viruses for replication Can only infect/replicate in host cells infected with another virus Adeno-associated virus (AAV) |
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Viroids |
Virus like agent that parasitizes plants 1/10 the size of virus Made of RNA lack a capsid/ other type of coasting Made of RNA lack a capsid/ other type of coasting |
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Infection |
Condition in which pathogenic microorganisms penetrate host defenses, enter tissues, and multiply |
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Pathogenic state |
• Cumulative effects of infection damage • Cumulative effects of infection damage• Disruption of tissues and organs• Results in disease • Disruption of tissues and organs • Results in disease |
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Disease |
Any deviation from health |
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Factors that cause disease |
InfectionsDietGeneticsAging |
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Infectious disease |
Disruption of tissue or organs caused by microbes or their products |
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Resident (Normal) Biota |
Large and diverse collection of microbes living on or in the bodyAka resident or indigenous biota or normal flora |
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Microorganisms are found all over the body. T or F. |
True |
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Human cells contain ___ (number) genes. microbes that inhabit humans contain __ genes. |
22,000, 8 million |
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We have a lot of microbes in places we used to think were sterile. T or F. |
True |
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All healthy people harbor ____ _____ _____ , but in low numbers |
potentially dangerous pathogens |
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Benefits of normal biota |
Influence the development of organsPrevent overgrowth of harmful microorganisms |
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What are the benefits of normal biota |
influence pos. development of organs, prevent the overgrowth of harmful microbes (antagonism) |
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Microbial antagonism |
"Good" microbes may keep intruder microorganisms from establishing Microbes in steady, established relationships are unlikely to be displaced by incoming microbes |
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Differences in gut microbiomes have been associated with differences in the risk for: |
Heart disease- Asthma- Autism- Rheumatoid arthritis- Even thoughts, moods, and propensity for mental illness |
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Endogenous infections |
Caused by biota already in the body Can occur when normal biota is introduced to site that was previously sterile, Example: E. coli entering the bladder -> UTI |
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Initial Colonization of Bacteria (Newborns) |
Fetuses are seeded with normal microbiota in utero Important for healthy full term pregnancies and healthy newborns |
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Breast milk contains around 600 species of bacteria and sugars that babies cannot digest. Why? |
Sugars used by healthy gut bacteria Breast milk may be necessary for maintaining healthy gut microbiome in the baby |
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Pathogen |
Microbe whose relationship with its host is parasitic, Results in infection and disease Severity of infections depends on pathogenicity of organism and condition of host |
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Pathogenicity |
Organism's potential to cause infection or disease |
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True pathogens |
Cause disease in healthy persons with normal immune defenses |
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What is pathogenicity |
An organisms potential to cause infection or disease ( ^ this, then ^ morbidity and mortality) |
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Opportunistic pathogens |
Cause disease in host w/ compromised immune defenses |
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Virulence |
Relative severity of disease caused by a microorganism |
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Virulence factor |
Characteristic or structure of the microbe that contributes to toxin production or induction of a harmful host response |
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Virulence Factors |
structures, products, or capabilities that allow pathogen to cause infection in host |
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Progress of an infection(5 steps) |
1.Entry2.Attaching to the host3.Surviving Host Defenses4.Causing Disease5.Vacating the Host |
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Portal of entry |
Characteristic route taken by microbe to initiate infection, Usually through skin or mucous membranes |
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Exogenous pathogen |
origination from outside the body(Environment, another person, or animal) |
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Endogenous pathogen |
already existing in body, Normal biota or previously silent infection |
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Sites of pathogen entry in skin |
Nicks• Abrasions• Punctures, some tiny• Conjunctiva- Mucous membrane covering the eye |
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Many microbes can enter the body through intact skin. T or F. |
False. Intact skin is very tough barrier that few microbes can penetrate |
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Microbes can enter the body through: |
Urogenital System(STDs)Respiratory SystemGastrointestinal TractBroken skinFetus gets microbes from placenta and when passing thru birth canal |
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How do microbes enter through the Gastrointestinal Tract? And survive harsh environment? |
Entry through food, drink, or other ingested substances Adapted to survive digestive enzymes and abrupt pH changes |
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Sexually transmitted infections are _% of infections worldwide. |
4 |
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In the US, there are _ million cases per year of sexually transmitted infections. |
13 |
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Sexually transmitted infections are transmitted through the skin or mucosa of: (5 things)
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penis vagina external genitalia cervix urethra |
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Some microbes enter a fetus through the __. |
placenta |
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Other infections can be transmitted as the child passes through the ___. |
birth canal |
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Infectious dose(ID) |
minimum number of microbes required for an infection |
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Pathogens are limited to only those cells and organisms to which they contact. T or F. |
False. Pathogens limited to what they can bind to, not everything they come in contact with they can bind to. |
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Some bacteria can survive inside phagocytes. T or F. |
True, ex HIV. |
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In what ways do virulence factors cause infection in the host?(3 ways) |
Directly through action of enzymedirectly through action of toxinsindirectly by inducing host's defenses |
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exoenzymes |
secreted by pathogenic bacteria, fungi, protozoa, and wormsbreak down and inflict damage on tissuesdissolve hosts's defense barriers and promote spread of microbes into deeper tissues |
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Exoenzymes |
Bacteria produce extracellular enzymes that dissolve intracellular connections and penetrate through or between cells to underlying tissues |
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Viruses secrete exoenzymes. T or F. |
False, viruses can't make proteins (enzymes are proteins). |
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exotoxin |
secreted by living bacterial cell to infect tissues, many types |
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Bacterial toxins |
chemicals produced by microbes,plants, and some animals: poisonous to other organisms |
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endotoxin |
not actively secreted, shed from outer membrane, only found in G- bacteria |
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___ are a lipopolysaccharide(LPS). |
endotoxins |
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Indirect damage caused by a microorganism results from? |
hosts's excessive or inappropriate response to a microorganism |
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localized infection |
microbe enters body and remains confined to specific tissue |
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What is a localized infection |
Microbe enters the body and remains confined to a specific tissue (boils, fungal skin infections and warts) |
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systemic infection
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A infection spreads to several sites and tissue fluids, usually in bloodstream
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Examples of viral systemic infection |
measles, chickenpox, aids |
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examples of bacterial systemic infection examples of bacterial systemic infection examples of bacterial systemic infection examples of bacterial systemic infection |
anthrax, typhoid fever, syphilis |
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examples of fungal systemic infection |
histoplasmosis, cryptococcosis |
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infectious agents can travel by means of nerves of cerebrospinal fluid. T or F. |
True |
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focal infection
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Infection exists when infectious agent breaks loose from local infection and is carried to other tissues
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What is a focal infection, examples |
Infectious agents that breaks loose from a local infection to another area; TB, streptococcal phyaryngitis (scarlet fever) |
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mixed infection |
several agents establish themselves simultaneously at the infection site |
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In some mixed infections, one microbe __ _ ______ that enables other microbes to invade. |
creates an environment |
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A primary infection is the ___ infection. |
initial |
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Secondary infection |
occurs when primary infection is complicated by another infection caused by a different microbe |
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acute infections |
come on rapidly, have short-lived effects |
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chronic infections |
progress and persist over long period of time |
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sign |
any objective evidence of disease as noted by observer |
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What is a sign |
We see a sign as we drive by a stop sign on a patient |
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symptom |
subjective evidence of disease as sensed by patient |
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syndrome |
disease identified or defined by certain complex of signs and symtoms |
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When does inflammation present itself during a disease? |
Earliest symptom of disease |
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Edema |
Accumulation of fluid in affected tissue |
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Granulomas and Abscesses |
Walled off collections of inflammatory cells and microbes in the tissues |
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Lymphadenitis |
Swollen lymph nodes |
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leukocytosis |
Increased # of white blood cells |
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Leukopenia |
Decreased # of white blood cells |
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Septicemia |
Microbes are multiplying in blood, present in large numbers |
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Bacteremia |
Few bacteria in the blood; not multiplying |
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Viremia |
Viruses in the blood; may be multiplying or not |
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Asymptomatic, subclinical, inapparent infections |
Host is infected but does not manifest disease Patient experiences no symptoms or disease and does not seek medical attention Can still infect people |
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Portal of exit |
Avenue of departure for pathogens to exit the host |
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Pathogens exit the host through:(5 things) |
Respiratory and Salivary PortalsSkin ScalesFecal ExitUrogenital Tract(vaginal discharge or semen)Blood or Bleeding |
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Pathogens that infect upper and lower respiratory tract can exit through:(4 things) |
Mucus• Sputum• Nasal drainage• Moist secretions |
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How do intestinal pathogens cause diarrhea? Why do they do this? |
Many intestinal pathogens cause intestinal irritation, increasing bowel motility Diarrhea provides rapid exit for pathogen |
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Agents involved in STIs leave host in _ or _. |
vaginal discharge, semen |
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Neonatal infections through the birth canal:3 |
Herpes simplex• Chlamydia• Candida albicans |
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Incubation period |
Time from initial contact -> appearance of first symptoms |
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Prodomal period . |
Earliest notable symptoms of infection
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Viral period
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Infectious agent multiplies at high levels and exhibits greatest virulence
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Convalescent stage |
Patient responds to infection and symptoms decline |
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Direct transmission to new host can be _ or _. |
Horizontal, Vertical |
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Communicable disease |
Pathogen is transmitted from one host to another |
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Contagious |
Agent is highly communicable, especially through direct contact |
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Vertical transmission |
Transmission from parent to offspring via ovum, sperm, placenta, or milk |
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Reservoir |
Primary habitat in natural world from which a pathogen originates • Often a human or animal carrier • Also soil, water, and plants |
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Transmitter |
individual or object from which an infection is acquired |
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Animal Vector |
Animal that transmits infectious agent between hosts, Most are Arthropods |
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Zoonosis |
Infection indigenous to animals but naturally transmissible to humans
Human is dead-end host and does not contribute to natural persistence of microbe
Spread of disease is promoted by close associations of humans w/ animals
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How is ebola an example of zoonosis? |
Ebola wants to be in bats, but ends up in humans |
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Nonliving Reservoir examples |
Water and soil harbor microbes that can sicken humans • Can also become temporarily contaminated w/ pathogens that come from humans Air:• Indoor air can serve as support medium for suspension of dispersal of respiratory pathogens via droplet nuclei and aerosols |
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How are water and soil a nonliving reservoir? |
harbor microbes that can sicken humans, Can also become temporarily contaminated w pathogens that come from humans |
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How is air a nonliving reservoir? |
Indoor air can serve as support medium for suspension of dispersal of respiratory pathogens via droplet nuclei and aerosols |
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Mechanism of bacteria adhesion |
Fimbriae (F), minute bristlelike appendages |
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Mechanism of adhesion of bacterial cell |
Adherentextracellular capsules (C) made of slime or other sticky substances |
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Method of adhesion of viruses |
Viral envelope spikes (S) |
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What are the 3 adhesion mechanisms (structures) by pathogens? |
Fimbriae Capsules Spikes |
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Toxins |
Toxins (primarily exotoxins) secreted by bacteria
diffuse to target cells, which are poisoned and disrupted
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Blocked phagocytic response |
Bacterium has a property that enables it to escape phagocytosis and remain as an “irritant” to host defenses, which are deployed excessively |
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Difference between endotoxins and exotoxins |
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Steps of disease |
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What are helminths? |
Worms (not microscopic, but included in study because disease transmitted similarly) |
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Is a virus an organism? |
No, because only has DNA or RNA in envelope of protein that cannot replicate without host, does not have ribosomes or cytoplasmic membrane. Called viron to get around this. |
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4. Describe the function and structure(s) of viral capsids. |
Capsids are protective shells around viruses that surround their nucleic information (the host cell makes them). A nueclocapsid contains both a capsid and the nucleic acids together |
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5. Distinguish between enveloped and naked viruses. |
Naked: Consist only of a nucleocapsid Enveloped: Has a piece of modified host cell membrane (for animal viruses only) that surround the capsid |
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6. Explain the importance of viral surface proteins, or spikes. |
Viral spikes are found on both naked and enveloped viruses that allow them to dock with a host cell |
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What are the possible nucleic acid configurations exhibited by viruses. |
Can be made from DNA (ss or ds) or RNA (ss or ds) |
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List the 5 steps in becoming established in the host. |
Portals of entry• Attaching to the host• Surviving host defenses• Causing disease• Vacating the host |
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List the portals of entry |
skin, GI (through food or other ingested things), Respiratory system (oral and nasal cavity and inhaled), UI (sex), Pregnancy and Birth (placenta) |
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List the portals of exit |
Respiratory and salivary (pathogens associated with resp. infections), Skin scales (always shedding), Fecal (mostly intestinal pathogens – helminthes release eggs, protozoa release cysts), Urogenital (pathogens associated with STIs), blood (Transmitted by ticks, fleas and mosquitoes) |
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6. Name and describe 3 adhesion mechanisms (structures) by pathogens. |
Spikes on the viruses, hooks or suckers on helminthes and certain receptors on bacteria that limit its scope of pathogenicity |
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7. List 3 ways pathogens fight the host’s process of phagocytosis.
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Pathogens use antiphagocytic factors to get around a hosts process of phagocytosis.
a)) Leukocidins: Kill phagocytes outrightb) Slime or capsule: makes it difficult for the phagocyte to avoid phagocytesc) Some bacteria actually want to live inside phagocytes
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