Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
125 Cards in this Set
- Front
- Back
|
Viral genome core
|
-Piece of nucleic acid
-contains either DNA or RNA, never both -May have 3 genes or several hundred |
|
|
Capsid
|
-protein shell surrounding the genome
-may be a very simple structure or complex |
|
|
First Virus
|
-found because it affected tobacco plant
-tobacco mosaic virus |
|
|
Viruses:
|
-thought to be "poison"
-smaller than bacteria -obligatory intracellular parasite consisting of a piece of nucleic acid surrounded by a protein coat -lack independent metabolism -do not have organelles or ribosomes -multiply inside living cells using the host cell's machinery |
|
|
Viral Terminology
|
-active=live
-inactive=dead -replicate=multiply |
|
|
Envelope
|
-some viruses have a lipid and carbohydrate coating in addition to the capsid, usually derived from the host cell
|
|
|
Naked viruses
|
-no envelope
|
|
|
Spikes
|
-protein projections associated with the envelope
-may mutate frequently |
|
|
Virion
|
-the extracellular state-when it is not in the host (also called viral particle)
-used interchangeably with virus |
|
|
Virus Groupings
|
-are grouped into families
-general groupings are the host type and nucleic acid content |
|
|
Groupings:Host type
|
-Animal viruses
-plant viruses -bacteriophages (viruses that infect bacteria) |
|
|
Groupings: Nucleic Acid content
|
-DNA or RNA viruses
-DNA viruses may be double or single stranded -RNA viruses may be positive or negative -Negative RNA viruses carry a special enzyme: RNA polymerase |
|
|
Culturing Viruses
|
-in bacteria (for bacteriophages only)
-in animals like mice, rats (difficult because causes different symptoms in different animals) -in embryonated poultry eggs -in cell cultures (primary cell cultures: live for a finite period of time and only form a mono layer) (continuous cell cultures: abnormal cells, immortal, live indefinitely. ) |
|
|
Viral Replication: Lytic Cycle
|
Immediately makes viruses and kills cell
|
|
|
Lytic Cycle: 1. Adsorption
|
random collision and adherence to complementary host receptor sites,
highly host cell specific!!!!!!!!!!!!!!! |
|
|
Lytic Cycle: 2. Penetration
|
nucleic acid core enters host cell, protein coating remains outside
|
|
|
Lytic Cycle: 3. Replication/Biosynthesis
|
vDNA takes over the host cell, directs production of viral component
|
|
|
Lytic Cycle: 4. Assembly/Maturation
|
viral components assemble into whole viruses, few hundred to several thousand
|
|
|
Lytic Cycle: 5. Release/Burst
|
lysis of host cell, releasing mature virions, each capable of infecting another cell.
|
|
|
Burst size
|
number of new viruses releases (50-200)
|
|
|
Burst time
|
time interval between attachment and burst (as little as 20 minutes)
|
|
|
Viral Replication: Lysogeny
|
Viruses insert vDNA in host DNA
-vDNA splices into host DNA and remains dormant until induced to undergo the lytic cycle -induced by: UV, light, radiation, chemicals, stress etc.. |
|
|
Prophage/Provirus
|
The virus when it is inserted into the host DNA
-this latency period "hides" the virus from the body's immune system |
|
|
Transduction
|
-viruses may carry new genes from host to host.
-may exhibit new characteristics, uses as a tool by researchers to splice genes for genetic recombination -also implicated in causing some forms of cancer |
|
|
Eukaryotic Cell Viral Replication
|
-requires specific receptor sites on eukaryote membranes
-Release is by cell burst (8-40 hours) or budding (enveloped viruses). Viruses may be released slowly for long time, not killing the host cell. -Non-enveloped viruses bind to potential host cell membrane and induce endocytosis. -Enveloped viruses fuse with host cell membrane and only core and proteins (enzymes) enter the host cell. -Replication and assembly much more complex. May occur in the cytoplasm or nucleus or both. Core must "deal" with nuclear membrane. Not well understood. Virus may use host cell's machinery or create its own. -Eukaryotic host cells may become transformed, possibly become immortal (linked to cancer) or induce immune reactions. -RNA viruses may use vRNA immediately or need to synthesize another strand of RNA to be used to create viral components. Retroviruses carry an enzyme, reverse transcriptase, to synthesize a strand of DNA. |
|
|
Reverse transcriptase
|
enzyme carried by retroviruses to synthesize a new strand of DNA
|
|
|
Cancer
|
-Estimated that 20% of all cancers are activated by viruses
-virus inserts at the site of an oncogene (part of the host gene) -Host cells are transformed into abnormal or immortal cancer cells. May produce abnormal products or abnormal amounts of normal cell products. -Cancer cells also undergo dedifferentiation - revert back to an embryonic-like form -May metastasize - spread to other body parts. -Overall, cancer cells interfere with normal organ processes and rob vital nutrients. |
|
|
Loss of contact inhibition
|
cells don't know when to stop dividing
|
|
|
Viral Detection
|
-In some cell cultures, see cytopathic (abnormal appearance) effect
-hemagglutination (clumping of red blood cells) -Some cells show characteristic changes (rabies causes Negri bodies in brain cells) -Some viral infections create specific signs in the human body |
|
|
Koch's Postulates
|
-cannot be applied to viral diseases because the virus cannot be cultivated in pure culture or there may not be a suitable animal model
|
|
|
Viral Treatment
|
-antibiotics dont work.
-Difficult to target unique biochemical systems in viruses (like in bacteria) |
|
|
Antiviral agents
|
work by blocking polymerase functions in viruses or base analogs that create non-functional viral DNA, thus prevent viral replication
|
|
|
Interferon
|
-different types produced by different host cells
-non-specific action -viral infection causes host cell to produce interferon -interferon exposure to surrounding non-infected cells induces them to produce anti-viral protein. -This protein acts as a barrier to provide protection for the uninfected cells. -Bad side effects often result from interferon administration |
|
|
Viral Inactivation
|
-usually by chemicals such as chlorine, iodine, phenol, detergents, heavy metals ant toxic gases. Also heat, UV.
-totally dependent on the individual virus. |
|
|
Virus-Like Agents: Viriods
|
Tiny fragments of RNA, all are plant pathogen (must be able to penetrate cellulose cell walls), can multiply inside insects to be passed to pollen or seeds
-suspected to be associated with human diseases-no direct evidence |
|
|
Virus-Like Agents: Prions
|
-proteinaceous infectious particle
-current theory is that these are normal proteins that become infectious when folded into abnormal shapes. -invisible to the immune system -Tough enough to survive harsh solvents and extreme temperatures -Examples: Bovine spongiform encephalopathy, Chronic Wasting Disease, Scrapie -Resistant to high heat, radiation, UV light, and disinfectants -human risk is by ingesting beef products -incubation 2-20 years |
|
|
RNA viruses
|
Contain RNA polymerase, which makes vRNA that host ribosomes use as mRNA to make viral components
|
|
|
Orthomyxoviruses
|
-influenza viruses, spikes mutate frequently
-yearly vaccine based on the predominant A and B strains (about 70% effective) -destroys the epithelial lining of the respiratory tract thus allowing secondary bacterial infection to enter -1-2 day incubation exposure -Types A, B, C |
|
|
Orthomyxoviruses: Type A
|
-responsible for pandemics that occure at intervals of 10-20 years
|
|
|
Orthomyxoviruses: Type B
|
-cause local outbreaks and epidemics less often
|
|
|
Orthomyxoviruses: Type C
|
-Type C strains are rare
|
|
|
Parainfluenza
|
Respiratory infections, milder than the flu, croup in children
|
|
|
Corona virus
|
-Common colds (1 of 3)
-severe acute respiratory syndrome (SARS)- first reported in China, mortality 10% |
|
|
Rhinoviruses
|
-most common colds (1 of 3)
-nasal passages are the modes of entry -can be shed for weeks |
|
|
Respiratory syncytial virus (RSV)
|
-respiratory infection in children, milder in adults.
-Linked to ear infections in children. -#1 cause of pneumonia in infants, highly contagious. |
|
|
Hepatitis A (HAV)
|
-infectious hepatitis
-fecal-to-oral route, -~1 month incubation, -~40% of people have been exposed, -least dangerous form, -preformed immunoglobulin can prevent 80-90% cases, -supportive treatment only, -liver damage can result. -Vaccine available. |
|
|
Hepatitis C
|
transmitted via blood contact and body fluids.
-Blood transfusion transmittance is rare, though still possible, since screening began in 1990. -Incubation 6 – 12 weeks. - Many cases asymptomatic or mild initially. -85% become chronic – 20 yrs or more with 20% leading to cirrhosis or liver cancer. |
|
|
Hepatitis D (Delta virus-HDV)
|
-co-infection with Hepatitis B
|
|
|
Hepatitis E (HEV)
|
-fecal to oral route
-new epidemics appearing in Asia, Africa, India, and Central America -rare in U.S. |
|
|
Hepatitis G
|
-transfusions and needle sticks
-not conclusive to liver disease |
|
|
Rubeola
|
-measles (highly contagious)
-Koplik's spots (red, white, and blue spots in mouth) -complications can be serious -measles during pregnancy can result in spontaneous abortion or premature delivery often with fetal death -vaccine available |
|
|
Rubella
|
-German measles, 3-day measles
-mild fever with rash -can cross placenta and cause congenital defects -especially during first trimester -vaccine available |
|
|
Mumps
|
-swelling of salivary glands
-meningitis follows in 10% of the cases -may cause sterility in adult males -vaccine available |
|
|
Rotavirus
|
-MOST COMMON cause of severe dehydrating diarrhea in children worldwide
|
|
|
Norwalk virus
|
viral gastroenteritis
|
|
|
Coxsackie virus
|
-implicated in a number of conditions such as chronic fatigue syndrome
-viral heart disease -possibly insulin-dependent diabetes |
|
|
Polio viruses
|
-can be mild to moderate
-fever and meningitis with recovery (mild) -paralytic involving central motor neuron defects (moderate/severe) -respiratory disfunction can occur in older patients -very stable virus -two vaccines available |
|
|
Yellow Fever
|
-transmitted by (Aedes aegypti) mosquitos
-cause hemorrhaging in liver and kidneys -mortality 80% -still endemic in Africa -vaccine available for travelers |
|
|
Dengue Fever
|
-most common mosquito-transmitted viral infection
-hemorrhagic fever -mortality 5-30% -military vaccine available |
|
|
Dengue Fever
|
-Most Common mosquito-transmitted viral infection, -hemorrhagic fever, mortality 5-30%
-military vaccine available |
|
|
West Nile Virus
|
-carried by Culex pipens mosquito
-feeds at night -likes stagnant cool water for breeding -symptoms mimic flu, can include a rash -supportive care only |
|
|
Rhabdo Virus
|
-rabies
-bullet shaped -found in most warm-blooded mammals -thought to be asymptomatic in bats -length of incubation varies in animals -usually long in humans therefore immune serum usually works when exposed |
|
|
Bunya virus
|
-hantavirus pulmonary symdrome (HPS)
-transmitted by rodent excreta, saliva, or urine -After HIV and rabies, the most lethal virus in the U.S> -incubation 1-5 wks |
|
|
Filo Virus
|
-long, thread-like viruses that often take the shape of a fishhook
-causes viral hemorrhagic fevers -spread by direct contact with infected blood -Ebola virus-fatality 90% -Marburg virus-fatality 25% |
|
|
Retroviruses
|
-unique
-contain enzyme-reverse transcriptase, which makes DNA from vRNA, inserts new DNA into host DNA -most are not cytolytic and may be expressed indefinitely. Many related to cancers. -Lentiviruses- typically have a long incubation period (human immunodeficiency virus (HIV) usually results in AIDS, destroys cells thus devastating the immune system) |
|
|
DNA Virus:
|
Tend to be larger, can replicate in a greater variety of cells
|
|
|
DNA Virus: Herpes Viruses
|
-lytic
-latent and highly contagious |
|
|
DNA Virus: Herpes Simplex Virus 1
|
-fever blisters, cold sores
|
|
|
DNA Virus: Herpes Simplex Virus 2
|
-Genital herpes, STD
-higher risk for cervical cancer among women -1/2 of the genetic code of HSV-1 and HSV-2 are identical |
|
|
DNA Virus: Varicella-Zoster
|
-chicken pox usually in children
-shingles in adults |
|
|
DNA Virus: Cytomegalovirus (CMV)
|
-mild to very severe in immumo-suppressed patients (abnormally large WBCs)
-estimated that 80% of the U.S. population may carry the virus. -In AIDS patients, can result in damage to the retina leading to blindness |
|
|
DNA Virus: Human Herpes virus 6 (HHV-6)-roseola
|
-High fever followed by rash
-Usually in children -now seen in AIDS patients |
|
|
DNA Virus: Epstein-Barr Virus (EBV)
|
-infectious mononucleosis
-fever, chills, enlarged spleen -may be latent and reoccuring -linked to cancer only found in central Africa |
|
|
DNA Virus: Human Herpes Virus 8 (HHV-8)
|
-probable cause of Kaposi sarcoma (purplish lesions on body) in AIDS patients
-Mainly in men AIDS patients |
|
|
DNA Virus: B Virus
|
-Herpes-like virus
-disease in Old World Monkeys -serious neurological symptoms -Primate keepers are at risk |
|
|
DNA Virus:Hepatitis B (HBV)
|
-lives in all body fluids
-Extremely contagious -frequently sexually transmitted -many times the means of transmission is unknown -incubation 4wks-6months -no successful tissue culturing -acute and chronic -full recovery is slow -carriers exist -can lead to liver cirrhosis and cancer -a recombinant (genetically engineered) vaccine available. |
|
|
DNA Virus: Adenovirus
|
-ARD (acute respiratory disease) or common colds also conjunctivitis (Pink Eye).
|
|
|
DNA Virus: Papova viruses-Human papillomavirus
|
-cause benign skin warts, some connection to cancer
-genital warts (STD)-90% ofa ll cervical cancers associated with this -may be linked to various other cancers -CDC estimates that 7.5 million women between the ages of 14 and 24 carry this virus -current vaccine protects against 4 strains that are found to occure 3.4% of women -most HPV are benign strains that cause no symptoms and usually dissappear on their own. |
|
|
DNA Virus: Parvovirus
|
-erythema infectiosum or Fifth disease
-fever and slapped cheek symdrome -primarily children |
|
|
DNA Virus: Pox Viruses
|
-largest viruses to infect humans
-smallpox (Variola) -death or severe disfigurement. Completely eradicated due to vaccine -Routine public vaccinations ceased in 1972. -Last known infection in Somalia, Africa 1977 -#1 potential bioweapon threat |
|
|
DNA Virus: Vaccinia
|
-cowpox
-cross reacts with variola -used in smallpox vaccine |
|
|
DNA Virus: Monkey Pox
|
-contracted from animal bites such as rats, prairie dogs, and lab monkeys
|
|
|
Mycology
|
-study of fungi
-over 100,000 identifiable different species |
|
|
Mycosis
|
any fungal infection
|
|
|
Fungi Characteristics
|
-large eukaryotic cells
-unicellular and multicellular forms -chemoheterotrophs-most are saprobes-a type of chemoheterotroph that produce extracellular enzymes to digest molecules in their surroundings then absorb nutrients. Most are decomposers -cell mombranes contain ergosterol in place of cholesterol found in animal cells -cell walls contain chitin -most are aerobes (yeast-facultative anaerobes) -most have complex life cycles, most reproduce asexually and sexually -many form spores as a form of reproduction -some are opportunistic pathogens to animals -most known plant diseases are fungal (molds, rusts, or smuts) -most prefer moderate temperatures -can tolerate high slat or sugar concentrations (can be used to create selective growth media) -prefer mildly acidic pH (also used to create growth media) -some have very diverse metabolism (can degrade hydrocarbons or cellulose) -Immunocompromised and diabetic patients are most susceptible to fungal infections |
|
|
Budding
|
-yeast reproduces this way
-a new cell forms at the surface of the original cell, enlarges, then breaks free to assume an independent existence -single celled |
|
|
Hyphae
|
-elongations of the cell without separation of newly formed cells that results in thread-like (filamentous)
|
|
|
Mycelium
|
-intertwined mass of hyphae
|
|
|
Conidia
|
-structures that produce microscopic spores formed from the hyphae
-clonidial structures are used for identification and classification. -spores are transported by air currents. -very common lab contaminants -allergies common |
|
|
Mushrooms
|
-an example of higher forms where hyphae are cemented together to form, large, structurally complex, fruiting bodies.
-the mushroom is actually the spore-producing structure -spores produced in the underneath gills of the cap. |
|
|
Rhizopus stolonifer
|
-common laboratory contaminant
-found on produce and breads -used in the industrial production of steroids, meat tenderizers, chemicals and certain coloring agents |
|
|
Penicillium notatum
|
-common lab contaminant
-source of antibiotic-penicillin |
|
|
Aspergillus flavus
|
-aspergillosis
-opportunistic pathogen -produces highly toxic aflatoxin, causes tumor formation in animals -common lab contaminant |
|
|
Histoplasma capsulatum
|
-histoplasmosis
-resembles TB -may be transported by machrophages -may be self-limiting or progressive and fatal -may develop immunity -may be detected by a skin test -associated with bird and bat droppings -primarily a disease of rural areas in Midwestern U. S. |
|
|
Dimorphic Fungi
|
-fungi that alternate body forms
-may exhibit the filamentous forms at cooler incubation temperature and the unicellular form at body temperature |
|
|
Blastomyces dermatitidis
|
-blastomycosis
-associated with dusty soil and bird droppings -spores enter through skin abrasions or inhaled -can be self healing or fatal |
|
|
Coccidioides immitis
|
-coccidiomycosis (San Joaquin Valley Fever)
-influenza-like symptoms -can be self-limiting or become disseminated throughout the body and affect many organs -spores found in soil of desert regions |
|
|
Cryptococcus neoformans
|
- cryptococcus
-most dangerous of all fungal diseases -associated with bird droppings and the soil -occurs world-wide. AIDS patients are extremely susceptible. |
|
|
Pneumocystis jiroveci (formerly carinii)
|
-the most common cause of non-bacterial pneumonia in HIV patients
-originally thought to be a protozoan, complex life cycle. |
|
|
Claviceps purpurea
|
-ergotism (LSD like symptoms)
-rye grain contaminant -widespread in the Middle Ages -causes bizarre behavior. |
|
|
Sporothrix schenkii
|
sporotrichosis
-transmitted by punctures -associated with horticultural activities. |
|
|
Saccharomyces ssp.
|
baker's yeast
|
|
|
Candida albicans
|
-normal oral and genital flora -opportunistic pathogen -causes thrush and vaginitis, -dimorphic - in deep infections
-the yeast form predominates, whereas in superficial infections of keratinized skin layers, the mycelial form is more common. (can cause amputation in diabetics if not treated) |
|
|
Stachybotrys chartarum
|
-slimy greenish black mold -grows in damp conditions -produces trichothecene mycotoxin that inhibits DNA replication, transcription and translation.
-Inhalation of spores can be fatal. |
|
|
Trichophyton, Epidermophyton, Microsporum
|
-dermatophytes
-All three can be involved in the following: -tinea pedis - athletes foot -tinea cruris - jock itch -tinea capitis - ringworm of the head -tinea corporis - ringworm of the body -tinea unguium - ringworm of the nails |
|
|
Kingdom Protista
|
-Eukaryotic Heterotrophs
-most unicellular -very diverse -Common Groupings: Protozoans |
|
|
Trophozoite
|
-free-living feeding form
|
|
|
Cyst
|
-dormant form
|
|
|
Protozoa
|
-unicellular
-lack cell walls -few are photosynthetic -four phyla grouped by form of motility -all aquatic -asexual and sexual reproduction |
|
|
Phylum Sarcodina
|
-amoeboid movement
|
|
|
Entamoeba hystolytica
|
-amebic dysentery or amoebiasis
-cysts ingested and trophozoite emerges and invades the intestinal lining -results in bloody diarrhea -some individuals may be asymptomatic |
|
|
Naegleria fowleri
|
-priamry ameobic meningoencephalitis (PAM)
-found in bodies of fresh water and soils -infection occurs during summer months when people swim in lakes -Many can be exposed but few rarely become infected -organism enters through the nasal passages and into the brain and spinal fluid -severe headache -can cause rapid death |
|
|
Acanthamoeba ssp
|
-granulomatous ameobic encephalitis (GAE) and keratitis (eye infection)
-found in bodies of fresh water -causes a slow infection in immunocompromised patients (like AIDS) -hard to treat -slow progression -Not usually found in healthy individuals -keratitis occurs in soft-lens contact wearers -can result in permanents eye damage and vision loss |
|
|
Phylum Mastigophora
|
-flagellates
|
|
|
Trypanosoma ssp
|
-typanosomiasis or African sleeping sickness-vector-tsetse fly
-Chagas disease-vector-kissing bugs -invades the blood due to the biting insects -Advance stages involve the CNS and ultimately death |
|
|
Trichomaona vaginalis
|
-trichomiasis (usually an STD)
-both sexual partners should be treated simultaneously |
|
|
Giardia lamblia
|
-giardiasis
-cyst now found in most fresh water sources worldwide -cysts are ingested, the trophozoite emerges and adheres to the small intestine wall, thus interfering with fat absorption -rarely invades the intestinal wall, therefore, no blood will be present in the stool. -some people become carriers (wildlife are carriers) |
|
|
Phylum Ciliata
|
-ciliated
|
|
|
Balatidium coli
|
-balantidiasis
-a rare form of dysentery -primarily a parasite of domestic animals |
|
|
Phylum Apicomplexa (Sporozoa)
|
-non-motile adult forms, all parasites
-complex life cycles |
|
|
Toxoplasma gondii
|
-toxoplasmosis associated with cats
-kitty litter boxes, sandboxes and gardens are the most common source of exposure -the parasite is passed in the cat feces. As the feces begin to dry, after about 24-48 hr., the cyst form becomes infective. Cysts can then become airborn. -humans infected by the ingestion of oocytes -most individuals develop lifelong immunity -some harbor the parasite in their bodies and it becomes active later in life. -parasite has an affinity for fetal tissue, brain and retina -may cause still birth or mental retardation -presence of antibodies may be detected by a simple blood test |
|
|
Cryptosporidium ssp.
|
-cryptosporidiosis
-usually aquired from ingestion of produce fertilized with human waste (almost always produce imported from mexico). -very low infectious dose level -incubation of one week |
|
|
Plasmodium vivax, P. malariae, P. ovale, P. falciparum (these are the four species that infect humans)
|
-malaria or blackwater Fever
-vector: Anopheles mosquito -KNOW THE LIFE CYCLE!!!! -P. Falciparum the worst of the species and almost always causes death |
|
|
Malaria Life Cycle-From Mosquito to Human
|
-Female mosquito bites
-sporozoite (infective form) transmitted via saliva -sporozoites carried by blood to liver -sporozoites enter the liver cells -In the liver cells they will undergo schizogeny (multiple fission) -Schizogeny releases merozoites (float in plasma of blood) -some will infect liver cells (cycle will continue) and some will enter RBCs (schizogeny occurs here and destroys the RBCs) -this cycle will continue to occur over and over causing a "fever cycle" -Few body defenses can fight them because they are intracellular. |
|
|
Malaria Life Cycle-From Human to Mosquito
|
-Some merozoites turn into gametocytes and stay in the plasma (female and male)
-Mosquio will bite into human and become infected with the gametocytes -these gametocytes unite (fertilize) in the mosquito stomach producing sporozoites -sporozoites carried to salivary glands |
