Term
| What is the morphology of cocci, rods, curved, snake-like and spiral organisms? |
|
Definition
| coccus, bacillus, vibrio, spirillum and spirochete |
|
|
Term
| What does a Gram Stain do? |
|
Definition
| Distinguish between two major classes of bacteria depending on staining of peptidoglycan layer. |
|
|
Term
| How does one do a Gram Stain? |
|
Definition
| Heat fix bacteria or dry onto a slide, stain with crystal violet, which precipitates with iodine, wash away unbound excess stain with acetone-based decolorizer, then counter-stain with safranin. |
|
|
Term
| What color are Gram pos and neg bacteria after Gram Stain? |
|
Definition
| Pos is purple because of thick peptidoglycan layer and neg is red because it didn't retain crystal violet in thin peptidoglycan layer |
|
|
Term
|
Definition
| Distinguishing strains of bacteria by using antibodies to detect characteristic antigens on the bacteria. |
|
|
Term
| What is an advantage of techniques such as DNA hybridization and PCR amplification? |
|
Definition
| Do not require living or growing bacteria and can be used for rapid detection and identification of slow growing organisms. |
|
|
Term
| Describe the bacterial chromosome. |
|
Definition
| Single, ds circle in a region called nucleoid; no histones; plasmids may exist |
|
|
Term
|
Definition
| May confer resistance to one or more antibiotics |
|
|
Term
| Describe the bacterial ribosome. |
|
Definition
| Consists of 30S+50S subunits forming 70s |
|
|
Term
| What is different about transcription and translation in bacteria from euk? |
|
Definition
|
|
Term
| What occurs on the cytoplasmic membrane of bacteria? |
|
Definition
| electron transport, energy production, uptake of metabolites, maintenance of membrane potential |
|
|
Term
| Does the cytoplasmic membrane of bacteria have sterols? |
|
Definition
| No, but euk cytoplasmic membrane does. |
|
|
Term
| How do prokaryotes reproduce? |
|
Definition
| asexually via binary fission |
|
|
Term
| What organelles are absent from the bacteria? |
|
Definition
| mitochondria, golgi bodies, ER, no real nucleus |
|
|
Term
| Where is the peptidoglycan layer located and what is another name for it? |
|
Definition
| Surrounds the cytoplasmic membrane and acts as part of the cell wall aka murein. |
|
|
Term
| What constitutes the cell wall of Gram-pos? |
|
Definition
| thick peptidoglycan, teichoic acid, and lipoteichoic acid |
|
|
Term
| What constitutes the cell wall of Gram-neg? |
|
Definition
| thin peptidoglycan, perplasmic space, outer membrane, proteins, LPS |
|
|
Term
| Where is LPS found and what is another name for it? |
|
Definition
| Found on the outer leaflet of the outer membrane of Gram neg; aka endotoxin. |
|
|
Term
| What is the area called between the external surface of the cytoplasmic membrane and the internal surface of the outer membrane? |
|
Definition
|
|
Term
| What is the glycocalyx and what is its importance? |
|
Definition
| The capsules and slime layers of bacteria; capsules are loose polysaccharide or protein layers while slime layers is less uniform; important for survival |
|
|
Term
| What is the difference between flagella and fimbriae (pili)? |
|
Definition
| Flagella are propellers that are anchored to the membrane through hook and basal body structures providing motility; fimbriae are hairlike structure that are smaller and promotes adherence |
|
|
Term
| Which bacteria class are spore formers and when does it occur? |
|
Definition
| Gram-positive only; under harsh conditions it converts from a vegetative state to a dormant state |
|
|
Term
| What is the structure of a spore? |
|
Definition
| Dehydrated, multishelled structure with a copy of a chromosome and a high concentration of Ca bound to dipicolinic acid; inner membrane, two peptidoglycan layers and outer keratin-like protein coat |
|
|
Term
| What triggers a spore to become vegetative? |
|
Definition
| Disruption to the outer coat by mechanical stress, pH, heat or another stresser; requires water and alanine |
|
|
Term
| What is the minimum requirement for growth in bacteria? |
|
Definition
| Carbon, nitrogen, energy course, water and various ions. |
|
|
Term
| Define intermediary metabolism. |
|
Definition
| The interrelated and tightly integrated processes of anabolism and catabolism. |
|
|
Term
| What are the two types of energy produced in bacterial glycolysis? |
|
Definition
| chemical and electrochemical |
|
|
Term
| What is bacterial glycolysis pathway called? |
|
Definition
| Embden-Meyerhof-Parnas pathway |
|
|
Term
| In the absence of oxygen, what represents the primary means of energy production? |
|
Definition
| Substrate-level phosphorylation; then the pyruvate may enter fermentation |
|
|
Term
| What are the 3 functions of the TCA cycle for bacteria? |
|
Definition
1) Most efficient mechanism for making ATP
2) Serves as final common pathway for complete oxidation of AA, FA and carbs
3) Supplies key intermediates for the ultimate synthesis of AA, lipids, purines, and pyrmidines |
|
|
Term
| What is the final pathway of glucose metabolism and its function? |
|
Definition
| Pentose P pathway; used to provide nucleic acid precursors and reducing power in the form of NADPH for use in biosynthesis. |
|
|
Term
| What makes the TCA cycle amphibolic? |
|
Definition
| It may function in the anabolic and catabolic functions of the cell. |
|
|
Term
| What are the 2 basic purposes of microscopy? |
|
Definition
| Initial detection of microbes and preliminary or definitive identification of microbes |
|
|
Term
| What is the difference in the machinery of light and dark microscopy? |
|
Definition
| A special condenser is used for dark to prevent transmitted light from directly illuminating the specimen. |
|
|
Term
| What is a limitation of lightfield microscopy? |
|
Definition
| The resolution of the image ie the ability to distinguish that two objects are separate and not one; darkfield is better at this. |
|
|
Term
| What is a disadvantage of darkfield microscopy? |
|
Definition
| Since light moves around and not through the organism, the internal structure cannot be studied. |
|
|
Term
| What are the 5 microscopic methods? |
|
Definition
1. brightfield ie light
2. darkfield
3. phase-contrast
4. fluorescent
5. electron |
|
|
Term
| Culture media can be subdivided into four general categories. |
|
Definition
1) enriched nonselective media
2) selective media
3) differential media
4) specialized media |
|
|
Term
| What is enriched nonselective media used to grow? |
|
Definition
| Organisms without fastidious growth requirements. |
|
|
Term
| What is selective or differential media used to grow? |
|
Definition
| Organisms that may be present in a mixture of other organisms; media is supplemented with inhibitors that suppress the growth of unwanted organisms. |
|
|
Term
| What is specialized media used to grow? |
|
Definition
| Specific organisms that may be fastidious or typically present in large mixtures of organisms. |
|
|
Term
| What is cell culture used to grow? |
|
Definition
| Organisms that are strict intracellular microbes; that is, they can only grow in living cells. |
|
|
Term
| How does site of collection influence which media to use? |
|
Definition
| Specimens from normally sterile sites are inoculated onto nonselective agars/broths while those with potential contamination are put on selective/differential media. |
|
|
Term
| Define pathogenicity island. |
|
Definition
| Large chromosomal regions that contain sets of genes encoding numerous virulence factors. |
|
|
Term
| What is the natural defense mechanism in openings of human body? |
|
Definition
| Mucus and ciliated epithelium, lysozyme, tears, acid and bile |
|
|
Term
| How are biofilms produced? |
|
Definition
| Once bacteria sense that sufficient bacteria are present to make a biofilm, they create a bacterial community bound within a sticky web of polysaccharide that binds the cells together and to the surface; called quorum sensing. |
|
|
Term
| Describe the structure of exotoxin. |
|
Definition
| Dimeric; B portion binds to specific cell surface receptor and A subunit is transferred into the interior of the cell where cell injury is induced. |
|
|
Term
| What are the biochemical targets of A-B toxins? |
|
Definition
| Ribosomes, transport mechanisms, intracellular signaling. |
|
|
Term
|
Definition
| Special group of toxins that activate T cells by binding simultaneously to a T-cell receptor and a MHCII molecule on an antigen-presenting cell. |
|
|
Term
|
Definition
| Proteins that can be produced by Gram-pos or neg bacteria, include cytolytic enzymes and receptor-binding proteins that alter function or kill the cell. |
|
|
Term
| What is the MOA of endotoxins? |
|
Definition
| Once released by Gram-neg (only), it binds to specific receptors on macrophages, B cells and stimulates release of acute-phase cytokines. |
|
|
Term
| What is the most important factor that determine success of a blood culture? |
|
Definition
| Volume of blood processed. |
|
|
Term
| What is the difference between continuous vs. intermittent septicemia? |
|
Definition
| Continuous occurs primarily in patients with intravascular infections; intermittent is with localized infections. |
|
|
Term
| How many bottles of media should be inoculated for blood cultures? |
|
Definition
|
|
Term
| What is the incubation period for blood culture? |
|
Definition
|
|
Term
|
Definition
| Disinfect pt skin before lumbar puncture, collected into sterile screw-capped tubes, centrifugated, sediment is inoculated; should be processed immediately |
|
|
Term
| How should urine samples be collected? |
|
Definition
| First portion of urine should be discarded; ideally cultured immediately |
|
|
Term
| What are the 5 general procedures used to detect bacteria in clinical specimens? |
|
Definition
1) microscopy
2) detection of bacterial antigens
3) detection of specific bacterial nucleic-acids
4) culture
5) detection of an Ab response to the bacteria |
|
|
Term
| What are two general forms of antimicrobial susceptibility tests performed in clinical lab? |
|
Definition
1) broth dilution tests
2) agar diffusion tests to obtain MIC |
|
|
Term
| What is the most common mechanism of antibiotic activity? |
|
Definition
| Interference with bacterial cell wall synthesis. |
|
|
Term
| What are the three vibrios that are important? |
|
Definition
| Vibrio cholerae, parahaemolyticus, and vulnificus |
|
|
Term
| What nutrient needs do vibrios have? |
|
Definition
| Must have salt, can tolerate wide pH range but are susceptible to stomach acids. |
|
|
Term
| Which serogroups of V. cholerae produce toxin? |
|
Definition
|
|
Term
| What is the structure of V. cholerae? |
|
Definition
| Polar flagella, toxin co-regulated pilus, lipolysaccharides with lipid A (endotoxin), core polysaccharide and O polysaccharide chain. |
|
|
Term
| What structure of the bacteria determine serogroup? |
|
Definition
|
|
Term
| What general classification of bacteria are Vibrio? |
|
Definition
| gram-negative, facultatively anaerobic, fermentative rods. |
|
|
Term
| How is the serogroup O1 for V. cholera further divided? |
|
Definition
| Three serotypes: Inaba, Ogawa and Hikojima and two biotypes: Classical and El Tor. |
|
|
Term
| Why doesn't V. cholera O1 spread beyond the confines of the intestine? |
|
Definition
| Because it does not produce a capsule. |
|
|
Term
| What is the genetic basis for V. cholera's ability to produce cholera toxin? |
|
Definition
| Bacteriophage CTXphi encodes the genes for the cholera toxin; the phage binds to the toxin co-regulated pilus and moves into the bacterial cell where it becomes integrated into the genome |
|
|
Term
| How is V. cholera spread and where does it reside in the environment? |
|
Definition
| Spread by consumption of contaminated food or water; found in estuarine and marine environments--assoc w/ chitinous shellfish |
|
|
Term
| What gives the "rice-water" stool look? |
|
Definition
| Proteinless, mucous filled watery stool. |
|
|
Term
| How is V. cholera diagnosed? |
|
Definition
| Microscopic examination of stool (not preferred); culture early in course of disease |
|
|
Term
| What is treatment for V. cholera? |
|
Definition
| Fluid and electrolyte replacement; azithromycine antibiotic |
|
|
Term
|
Definition
| Predilection for viruses to infect certain cells and not others. |
|
|
Term
| Tropism is defined by four factors. What are they? |
|
Definition
1) expression of host cell receptors for the virus
2) presence of cellular transcription factors that recognize viral enhancer and promoter sequences
3) anatomic barriers
4) local temp, pH and host defenses |
|
|
Term
| What is some major determinants of tissue tropism? |
|
Definition
| Presence of viral receptors on host cells, ability of the virus to replicate inside some cells but not in others, physical barriers. |
|
|
Term
| What are three ways viruses can damage or kill cells once inside? |
|
Definition
1) direct cytopathic effects
2) antiviral immune responses
3) transformation of infected cells |
|
|
Term
|
Definition
| Inability to recover infectious particles from cells that harbor the virus. |
|
|
Term
| What is general structure of Herpesvirus? |
|
Definition
| Large encapsulated viruses that have a ds DNA genome that encodes ~70 proteins. |
|
|
Term
| What is the pattern of infection like from Herpesvirus? |
|
Definition
| Causes acute infection followed by latent infection in which the viruses persist in a noninfectious form with periodic reactivation and shedding of infectious virus. |
|
|
Term
| Where do HSV-1 and 2 spread to? |
|
Definition
| Sensory neurons that innervate primary sites of replication, which is the site of entrance of virus. |
|
|
Term
| Where does HSV establish latent infection? |
|
Definition
| innervating ganglia of neuronal cell bodies |
|
|
Term
| What happens during HSV latency? |
|
Definition
| Viral DNA remains within the nucleus of the neuron and only latency-associated viral RNA transcripts (LATs) are synthesized. No viral proteins are produced. |
|
|
Term
| What are long-term morbidities associated with HSV? |
|
Definition
| corneal blindness, fatal sporadic encephalitis |
|
|
Term
| What are general morphologies of HSV? |
|
Definition
| Large, pink to purple intranuclear inclusions (Cowdry Type A) with chromatin pushed to edges of nucleus; inclusion bearing multinucleated syncytia. |
|
|
Term
| How does HSV present on the skin? |
|
Definition
| Fever blisters around mucosal orifices where it is bilateral and independent of skin dermatomes. |
|
|
Term
| Define gingivostomatitis. |
|
Definition
| Caused by HSV-1; occurs in children; swollen, erythematous HSV lesions of fingers; vesicular eruption from tongue to retropharynx causing cervical lymphadenopathy. |
|
|
Term
| What are the two types of corneal lesions caused by HSV? |
|
Definition
| Epithelial keratitis, which is virus-induced cytolysis of superficial epithelium and stromal keratitis, infiltrates of mononuclear cells around keratinocytes and endothelial cells. |
|
|
Term
| What is kaposi vericelliform eruption? |
|
Definition
| Generalized vesiculating involvement of skin. |
|
|
Term
| What is eczema herpeticum? |
|
Definition
| Confluent, pustular, or hemorrhagic blisters. |
|
|
Term
| What are the 3 serotypes and 2 biotypes of V. cholerae O1? |
|
Definition
| Inaba, Ogawa Hikojima; Classical, El Tor |
|
|
Term
| What are the three basic types of cell cultures for viruses? |
|
Definition
Primary cultures: dispersing cells from freshly removed host tissues
Secondary cultures: diploid cell lines and continuous cell lines |
|
|
Term
| What is the difference between diploid and continuous cell lines? |
|
Definition
| Diploid has undergone a change that allows their limited culture while continuous are capable of prolonged growth derived from diploid. |
|
|
Term
| Where are inclusion bodies located in HSV infected cells? |
|
Definition
|
|
Term
| What is almost always the final step in viral purification? |
|
Definition
| Density gradient centrifugation. |
|
|
Term
| What pH range are viruses stable at? |
|
Definition
|
|
Term
| What does radiation do to viruses? |
|
Definition
| Inactivates its infectivity. |
|
|
Term
| What does ether susceptibility distinguish on viruses? |
|
Definition
| Whether they possess an envelope or not. |
|
|
Term
| What do nonionic detergents do to viruses? |
|
Definition
| Solubilize lipid constituents of viral membranes. |
|
|
Term
| What does formaldehyde do to viruses? |
|
Definition
| Destroys viral infectivity by reacting with nucleic acid. |
|
|
Term
| How are viruses inactivated with a photodynamic process? |
|
Definition
| Penetrate with a dye and exposure to light will inactivate. |
|
|
Term
| What are some methods of sterilization? |
|
Definition
| Pressure, dry heat, ethylene oxide, and gamma-irradiation. |
|
|
Term
| What are the three potential outcomes of cell infected with a virus? |
|
Definition
1. failed infection (abortive)
2. cell death (lytic)
3. replication without cell death (persistent) |
|
|
Term
| What are the 4 types of persistent infections? |
|
Definition
1) chronic
2) latent
3) recurrent
4) transforming |
|
|
Term
| What is the difference between a nonpermissive and a permissive cell? |
|
Definition
| Nonpermissive may lack a receptor that will not allow replication of a particular type or strain of virus. Permissive provides the biosynthetic machinery to support the replicative cycle of the virus. |
|
|
Term
| Define semipermissive cell. |
|
Definition
| Inefficient replication of a virus; some steps are supported but not all |
|
|
Term
| What are lytic infections? |
|
Definition
| When virus replication kills the target cell. |
|
|
Term
| Define syncytia and what triggers it. |
|
Definition
| Fusion of neighboring cells into multinucleated giant cells; triggered by cell surface expression of viral glycoproteins. |
|
|
Term
| What does syncytia formation allow the virus to do? |
|
Definition
| Spread from cell to cell and escape antibody detection. |
|
|
Term
|
Definition
| Sustainable structure that appear within nucleus or cytoplasm; results from virus-induced changes in the membrane and may represent sites of viral replication or accumulation of viral capsids. |
|
|
Term
| What are a couple of nonlytic infections? |
|
Definition
|
|
Term
| What is the nature of HSV's latent infection? |
|
Definition
| Occurs in neurons that lack the nuclear factors required to transcribe the immediate early viral genes. |
|
|
Term
| What are 3 ways that oncogenic viruses immortalize cells? |
|
Definition
1) activate or provide growth-stimulating genes
2) remove the inherent braking mechanisms that limit DNA synthesis and cell growth
3) prevent apoptosis |
|
|
Term
| What lab methods accomplish (5)? |
|
Definition
1. description of virus-induced CPEs on cells
2. electron microscopic detection of viral particles
3. isolation and growth of virus
4. detection of viral components
5. evaluation of patient's immune response to the virus |
|
|
Term
| When should specimens be collected for viral infections? |
|
Definition
| Early in the acute phase of infection, before the virus ceases to be shed. |
|
|
Term
|
Definition
| Changes in cell morphology, cell lysis, vacuolation, syncytia, and inclusion bodies. |
|
|
Term
| What kind of viruses is electron microscopy useful for? |
|
Definition
| Detection of enteric viruses. |
|
|
Term
| How does one obtain a primary cell culture? |
|
Definition
| Dissociate specific animal organs with trypsin or collagenase; cells grown in monolayers or in suspension in artificial media. |
|
|
Term
| What is tissue culture dose (TCD50)? |
|
Definition
| Titer of virus that causes CPEs in half the tissue culture cells. |
|
|
Term
| What is lethal dose (LD50)? |
|
Definition
| Titer of virus that kills 50% of a set of test animals. |
|
|
Term
| What is infectious dose (ID50)? |
|
Definition
| Titer of virus that initiates a detectable symptom, antibody, or other response in 50% of a set of test animals. |
|
|
Term
| What can be used to detect viral antigens on the cell surface or within cells? |
|
Definition
|
|
Term
| What can be used to detect virus or antigen released from infected cells? |
|
Definition
|
|
Term
| What is the genetic fingerprint of viruses? |
|
Definition
| Electrophoretic patterns of RNA or restriction endonuclease fragment lengths from DNA viral genomes. |
|
|
Term
| What can be measured by real-time PCR? |
|
Definition
| Quantification of amount if virus within a patient (viral load); concentration of viral genome in a blood sample is proportion to the rate of PCR amplification of genomic DNA |
|
|
Term
| How does Southern blot analysis work? |
|
Definition
| Viral genome of electrophoretically separated restriction endonuclease cleavage fragments of the genome are blotted onto nitrocellulose filters and then detected by hybridization to DNA probes. |
|
|
Term
| How does Northern blot work? |
|
Definition
| Electrophoretically separated viral RNA is blotted onto a nitrocellulose filter in the same way as Southern but probing is different. |
|
|
Term
| What is transcription-based amplification? |
|
Definition
| Uses reverse transcriptase and viral sequence specific primers to make a cDNA and attaches a sequence recognized by the DNA-dependent RNA polymerase. |
|
|
Term
|
Definition
| Like antibodies to detect virus via sequence complementary to specific regions of a viral genome. |
|
|
Term
| What is structure of HSV? |
|
Definition
| linear ds DNA enveloped in DNA core, which is an icosadeltahedral capsid, surrounding is the tegument with viral proteins and enzymes, entirely covered by glycoprotein-containing envelope |
|
|
Term
| What are HSV early proteins (alpha)? |
|
Definition
| Proteins important for the regulation of gene transcription and takeover of the cell. |
|
|
Term
| What are HSV early proteins (beta)? |
|
Definition
| Transcription factors and enzymes, including DNA polymerase. |
|
|
Term
| What are HSV late proteins (gamma)? |
|
Definition
| Structural proteins, which are generated after viral genome replication has begun. |
|
|
Term
| What are the roles of HSV RNA polymerase and DNA polymerase? |
|
Definition
| RNA pol transcribes the viral genome and DNA pol replicates it. |
|
|
Term
| How many proteins and glycoproteins are encoded by the HSV genome? |
|
Definition
| 80 proteins and 10 glycoproteins. |
|
|
Term
| HSV causes lytic infections in what cells? |
|
Definition
| Fibroblasts and epithelial cells. |
|
|
Term
| HSV causes latent infections in what cells? |
|
Definition
|
|
Term
| What are the CPEs of HSV? |
|
Definition
| syncytia, "ballooning" cytoplasm, Cowdry Type A intranuclear inclusions |
|
|
Term
| Where can HSV be obtained from? |
|
Definition
| Vesicles but not crusted lesions. |
|
|
Term
|
Definition
| Means to identify CPEs by scraping the base of a lesion. |
|
|
Term
| How does ACV work as an anti-HSV drug? |
|
Definition
| ACV is phosphorylated by the viral thymidine kinase and cellular enzymes activates the drug as a substrate for the viral pol; the drug is incorporated into viral DNA to prevent its elongation. |
|
|
Term
| What kind of parasites are viruses? |
|
Definition
|
|
Term
|
Definition
| aka virus particle consists of a nucleic acid genome packaged into a protein coat (capsid) or a membrane (envelope). |
|
|
Term
| What does the outer layer of the virion do? |
|
Definition
| Package, protection, and delivery vehicle during transmission of the virus from one host to another and for spread within the host to the target cell. |
|
|
Term
|
Definition
| Viral attachment protein that mediate the interaction of the virus with the target cell. |
|
|
Term
| What kinds of subunits do viral capsid proteins associate? |
|
Definition
| Protomers, capsomeres and a recognizable procapsid. |
|
|
Term
| Where is the envelope of a virus obtained from? |
|
Definition
| Target cellular membranes even though cellular proteins are rarely found on it. |
|
|
Term
| What are VAPs that bind to RBCs? |
|
Definition
|
|
Term
| Which viruses are always enveloped? |
|
Definition
| All the negative-strand RNA viruses. |
|
|
Term
| What does the mechanism of viral internalization depend on? |
|
Definition
| Virion structure and cell type |
|
|
Term
| How do nonenveloped viruses enter the cell? |
|
Definition
| Endocytosis or viropexis. |
|
|
Term
| What cellular machinery do DNA viruses use to make mRNA? |
|
Definition
| DNA-dependent RNA polymerase II |
|
|
Term
| What cellular machinery do RNA viruses use to make mRNA? |
|
Definition
| They must encode it themselves in the cytoplasm because cell can't replicate RNA. |
|
|
Term
| How is viral DNA replicated? |
|
Definition
| Similarly as cellular DNA; initiated at ori sequence where it is recognized by DNA-dependent DNA polymerase; semi-conservative, DNA pol requires a primer |
|
|
Term
| What is the difference bw positive and negative-strand RNA viral genomes? |
|
Definition
| Naked pos-strand is sufficient to initiate infection by itself; neg-strand is not infectious by itself and a pol must be carried into the cell with the genome. |
|
|
Term
| Where are viral glycoproteins synthesized? |
|
Definition
| On membrane-bound ribosomes; have AA sequences to allow insertion into the RER and N-linked glycoslyation. |
|
|
Term
|
Definition
| Obligate, intracellular molecular parasite that lacks a cell wall and organelles, incapable of respiratory metabolism, composed of RNA and/or DNA within a protein coat that itself may be enveloped with lipoprotein membrane |
|
|
Term
|
Definition
| Infectious, nucleic-acid-free aggregates of a cellular protein expressed normally and primarily in neurons. |
|
|
Term
|
Definition
| Naturally occurring, highly stable, protein-free RNAs that infect and replicate in plant cells. |
|
|
Term
|
Definition
| cubic icosahedral symmetry |
|
|
Term
| Which membranes can the viral envelope come from? |
|
Definition
|
|
Term
| How is it determined where the virus obtains its envelope? |
|
Definition
| Determined by virus-directed reorganization of the cellular membrane to include virus-specified glycoproteins and to exclude the bulk of resident cellular proteins. |
|
|
Term
| When exactly is the envelope acquired? |
|
Definition
| When the capsid or nucleocapsid "buds" or evaginates through the altered cell membrane |
|
|
Term
| Does the virion envelope contain cellular proteins? |
|
Definition
| No, but it contains a lipid bilayer taken from the cell membrane. |
|
|
Term
| Why would viral envelopes be slightly different from its original site of acquisition? |
|
Definition
| Because there is a redistribution of cellular lipids as the viral proteins are implanted in the cell membrane. |
|
|
Term
| What are the two general ways by which an envelope coats or adheres to the internal capsid or nucleocapsid? |
|
Definition
1) Envelope may adhere directly to the capsid during the course of budding.
2) Capsid or nucleocapsid may be covered with a scaffold of matrix proteins to which the envelope adheres. |
|
|
Term
| What is the role of the myristate moiety in envelope interaction with substructure? |
|
Definition
| Causes substructure protein to adhere to cytoplasmic face of membrane involved. |
|
|
Term
| What is the structure of peplomers? |
|
Definition
| Oligomeric glyproteins of viral envelopes; complex of 2 or 3 different proteins, one of which is a integral membrane protein bound noncovalently to portion of integral protein protruding on surface of virion |
|
|
Term
| What are roles of peplomers? |
|
Definition
| Site by which enveloped virus can attach to a host and elicits immune response in the host |
|
|
Term
| What glycosylates viral integral membrane proteins? |
|
Definition
| Cellular enzymes in the ER and Golgi; but NOT via viral enzymes |
|
|
Term
| What do peplomers display? |
|
Definition
| Ligand for a cellular receptor and antigen that elicits neutralizing antibodies. |
|
|
Term
| How do peplomers appear under the microscope? |
|
Definition
| "spikes" or "knobs" or fine "bristles" arranged icosahedrally |
|
|
Term
| What are matrix proteins? |
|
Definition
| Scaffolding proteins that undergird the envelope of viruses; interacts with cytoskeleton to receive nucleocapsids deliver through it for envelopment |
|
|
Term
| What is the result of myristilating matrix proteins? |
|
Definition
| Causes their migration to and association with inner leaflet of cell PM, ER or Golgi membrane |
|
|
Term
| Where do viral capsid come from? |
|
Definition
| Encoded from viral genome |
|
|
Term
| How is the viral capsid assembled? |
|
Definition
| By capsomers spontaneously without use of energy by noncovalent interactions of the component proteins. |
|
|
Term
| What are the 3 known arrangements of nucleic acids with capsids? |
|
Definition
1) DNA is in "liquid crystal" state interacting directly with inner surface of capsid
2) pack into a core
3) genome is a nucleosome that is packaged into capsids |
|
|
Term
| Define nucleocapsid and which viruses usually have this? |
|
Definition
| Combo of nucleic acid and capsid; usually for viruses with helical symmetry |
|
|
Term
| What is a capsomer and the different shapes it assumes? |
|
Definition
| Final pre-fabricated protein units that make up a capsid; if it has 5 protomers, it is a pentamer; if it has 6 protomers, it is a hexamer |
|
|
Term
|
Definition
| Smallest recognizable structural sub-assembly of a capsid or nucleocapsid. |
|
|
Term
| What is the composition of a protomer? |
|
Definition
| Made of 3-4 polypeptides that share a tertiary motif known as "B-barrel jelly roll" |
|
|
Term
| How are protomers similar to capsids? |
|
Definition
| Assembled spontaneously with reversible state. |
|
|
Term
|
Definition
| complex of viral NA, replicative proteins, and packaging proteins that is housed within an icosahedral capsid. |
|
|
Term
| What are the two symmetries of viruses? |
|
Definition
| Icosahedral (cubic) and helical |
|
|
Term
| What is one consistent feature of DNA viruses? |
|
Definition
| Only ONE molecule of DNA constitutes the genome. |
|
|
Term
| All viruses are haploid except one, which is diploid. Which? |
|
Definition
|
|
Term
| What does it mean to be of positive polarity? |
|
Definition
| Refers to the fact that genomes of some RNA viruses are infectious because the genomic RNA can serve directly as mRNA to initiate viral protein synthesis and multiplication. |
|
|
Term
| What does it mean to be of negative polarity? |
|
Definition
| RNA viruses with non-infectious genomes where it cannot serve as mRNA; its polarity is opposite to that of its mRNA; requires transcriptase |
|
|
Term
| Where do virion lipids originate from? |
|
Definition
| Host lipid in cellular membranes. |
|
|
Term
| What enzymes can be found in the virion? |
|
Definition
| DNA-dependent RNA pol; RNA-dependent RNA pol; RNA-dependent DNA pol |
|
|
Term
| What enzymes can the virus encode that is not contained in the virion? |
|
Definition
| DNA-dependent DNA pol; RNA-dependent RNA pol |
|
|
Term
| Which HOST enzymes do viruses depend on? |
|
Definition
| host DNA-dependent pol and host DNA-dependent RNA pol |
|
|
Term
| Compare viral multiplication vs. replication. |
|
Definition
| Multiplication is production of progeny virus from the original infecting virus; replication is the synthesis of new genomes from the original template (one step of multiplication) |
|
|
Term
| How does length of time for viral multiplication compare for RNA vs. DNA viruses? What is drawback for RNA? |
|
Definition
| RNA viruses takes less time than DNA; higher mutation rates. |
|
|
Term
| What is multiplication time NOT dependent on? |
|
Definition
|
|
Term
| What are the two portals through viruses gain access into body? |
|
Definition
|
|
Term
| What are the 9 steps of viral multiplication cycle? |
|
Definition
1) recognition
2) attachment
3) penetration
4) uncoating
5) transcription
6) translation
7) genome replication
8) assembly
9) release |
|
|
Term
| How do human viruses adsorb to cells (2)? |
|
Definition
| single cellular receptor or both a receptor and co-receptor |
|
|
Term
| Describe one-step adsorption. |
|
Definition
| Recognition of a susceptible cell and attachment are accomplished simultaneously by the adsorption site on the surface of the virion. |
|
|
Term
| Describe two-step adsorption. |
|
Definition
| Recognition is the binding of the virus to its receptor, which may help induce the attachment, which is binding to the co-receptor. |
|
|
Term
| Explain tissue tropism and host specificity. |
|
Definition
| Infection depends on the virus being in the right tissue in the right host; mere act of adsorption does not guarantee infection. |
|
|
Term
| What does it mean that virions are metastable? |
|
Definition
| various components are in conformations that are energetically favorable but not not at their minimum energy levels. |
|
|
Term
| What environmental condition is important in penetration? |
|
Definition
| Process is temperature-dependent |
|
|
Term
| What are the 4 mechanisms of penetration? |
|
Definition
1) pore formation
2) fusion
3) receptor-mediated endocytosis
4) caveolation |
|
|
Term
| Where does the energy come from for viral penetration? |
|
Definition
|
|
Term
| What are four mechanisms of uncoating? |
|
Definition
1) pore formation at PM
2) fusion at PM
3) endosomal acidification
4) caveolation |
|
|
Term
|
Definition
| Structural assemblage of viral genomes and proteins into nucleocapsids. |
|
|
Term
|
Definition
| Finishing of protein cleavages in situ within the maturing particle and/or the acquisition of an envelope. |
|
|
Term
| What do cellular and viral proteins targeted to enter the nucleus share? |
|
Definition
| Nuclear localization signals (NLSs) that also specify direction |
|
|
Term
| How does transport from RER to PM occur? |
|
Definition
| Normal cellular vesicular trafficking. |
|
|
Term
| What does acylation with myristate or farnesol do to viral proteins in the cytoplasm? |
|
Definition
| Target the proteins to the inner lamella of the PM, where they interact with capsid proteins in the cytoplasm and with transmembrane portions of envelope proteins in the plasma |
|
|
Term
| What do ER molecular chaperones do for viral proteins? |
|
Definition
| Prevent premature folding and oligomerization. |
|
|
Term
| What are packaging signals? |
|
Definition
| Molecular tags recognized by capsid or other proteins involved in packaging the correct NA. |
|
|
Term
| Where are packaging signals absent from? |
|
Definition
| sub-genomic mRNAs and in negative strands which serve only as templates for mRNA synthesis |
|
|
Term
| How is the exit of DNA viruses controlled? |
|
Definition
| By the quantitative accumulation and action of proteins that mediate packaging |
|
|
Term
| How is it ensured that viral NAs and proteins are not wastefully overproduced? |
|
Definition
| Components are produced in quantities sufficient to produce large numbers of infectious progeny despite the concurrent, accidental production of even larger numbers of defective particles; localized concentrations of viral components are high enough to obey the law of mass action and drive assembly of virions. |
|
|
Term
| Assembly is a spontaneous process, t/f? |
|
Definition
|
|
Term
| What are the two pathways of viral genome packaging? |
|
Definition
| sequential assembly or concerted assembly |
|
|
Term
| What does the release of progeny virus from the infected cell depend on? |
|
Definition
| assembly of nucleocapsids and accumulation of a critical mass of proteins and virions |
|
|
Term
| What are the three general mechanisms by which progency virions leave the infected cell? |
|
Definition
| lysis, budding from PM and exocytosis |
|
|
Term
|
Definition
| At a critical level of toxicity (due to high concentration of viral protein), cell lyses and virions are released. |
|
|
Term
|
Definition
| Consequences to infection at the cellular level |
|
|
Term
|
Definition
| Cells to which viruses can absorb and into which they can penetrate. |
|
|
Term
|
Definition
| Cells that support viral multiplication. |
|
|
Term
|
Definition
| Cells that are susceptible to infection but the virus can multiply and be released at minimally detectable levels. |
|
|
Term
| What are the four types of infection at the cellular level? |
|
Definition
1) productively
2) latently
3) abortively
4) oncogentically |
|
|
Term
| What does the type of infection dependent on? |
|
Definition
| Susceptibility of the cell and species of the virus. |
|
|
Term
| Why shouldn't oncogenic transformation be considered as a latent infection? |
|
Definition
| Because oncogenic viruses do not multiply at all in cells which they can transform. |
|
|
Term
| How are human beings infected with HSV? |
|
Definition
| Latently and thus, inapparent. |
|
|
Term
| What viral properties are CPEs dependent on? |
|
Definition
| Site of replication, involvement with cell membranes, cell fusion activity with envelope proteins |
|
|
Term
|
Definition
1) margination of chromatin
2) inclusion bodies
3) vacuolization
4) cell fusion
5) giant cells
6) necrosis
7) apoptosis
8) transformation |
|
|
Term
| CPEs are observable by light or electron microscopy? |
|
Definition
|
|
Term
| The virus can cause cell damage in what 7 ways? |
|
Definition
1) inhibition of host cell macromolecular synthesis
2) alterations in host-cell gene regulation
3) breakdown of cell lysosomes and/or ER and Golgi
4) toxicity of accumulated viral protein
5) alterations in normal cellular metabolism
6) appearance of new antigenic determinants on the cell surface
7) binding of viral ligand to its cell receptor |
|
|
Term
| What is the sequence of events of the infecting virus on the target cell? |
|
Definition
1) adsorption
2) penetration
3) uncoating
4) transcription
5) translation
6) replication of genome
7) assembly
8) maturation
9) release |
|
|
Term
| What is the virulence of clostridial species related to? |
|
Definition
| ability to survive exposure to oxygen by forming spores and producing many diverse toxins ande nzymes |
|
|
Term
| What organisms causes nontraumatic myonecrosis? |
|
Definition
|
|
Term
| Patients with which chronic conditions are most susceptible to C. septicum? |
|
Definition
| occult colon cancer, acute leukemia and diabetes |
|
|
Term
| What is the human disease caused by C. septicum? |
|
Definition
| gas gangrene and septicemia |
|
|
Term
| Define the structure of C. perfringens. |
|
Definition
| large, rectangular, gram-positive rod, nonmotile, spores are rarely observed |
|
|
Term
| What is the most important toxin to C. perfringens and its effects? |
|
Definition
| Alpha toxin--lyses RBCs, platelets, WBCs and endothelial cells; mediates hemolysis, increased vascular permeability and bleeding, tissue destruction |
|
|
Term
| When is the C. perfringens enterotoxin produced? |
|
Definition
| during the phase transition from vegetative cells to spores and released with formed spores when cells undergo terminal stages of sporulation. |
|
|
Term
| What conditions in the small intestine stimulate sporulation? |
|
Definition
|
|
Term
| Where can C. perfringens survive within and outside the body? |
|
Definition
| Infections occur in the intestinal tract of humans; outside it is in soil and water contaminated with feces |
|
|
Term
| What are the 3 types of soft-tissue infections caused by C. perfringens? |
|
Definition
1) cellulitis
2) fasciitis
3) myonecrosis or gas gangrene |
|
|
Term
| In what ways can C. perfringens manifest? |
|
Definition
| soft tissue infections, food poisoning, necrotizing enteritis, septicemia |
|
|
Term
|
Definition
| localized edema and erythema with gas formation in soft tissue, generally nonpainful |
|
|
Term
| Define suppurative myositis. |
|
Definition
| accumulation of pus (suppuration) in the muscle planes w/o muscle necrosis or systemic symptoms |
|
|
Term
|
Definition
| painful, rapid destruction of muscle tissue; systemic spread with high mortality |
|
|
Term
| What is the laboratory diagnosis of C. perfringens? |
|
Definition
| microscopic detection of gram-pos rods in clinical specimens or recovery of organisms in feces collected within 1 day of onset |
|
|
Term
| What is treatment for C. perfringens? |
|
Definition
| Aggressive treatment with surgical debridement and high-dose penicillin therapy. |
|
|
Term
| What is the main purpose of fungi? |
|
Definition
| to degrade organic matter |
|
|
Term
| Fungi exist as heterotrophs in what 4 classes? |
|
Definition
1) saprobes
2) symbionts
3) commensals
4) parasites |
|
|
Term
| How are the cell wall and cell membrane unique for fungi? |
|
Definition
| Cell wall contains chitin and glucan while cell membrane contains ergosterol in lieu of cholesterol |
|
|
Term
| How are yeast and molds different by morphology? |
|
Definition
Yeast produces by budding/fission to yield pseudohyphae, unicellular, round, pasty, mucoid colonies on agar;
Mold are multicellular with threadline tubular structures called hyphae, colonies are filamentous, hairy or woolly |
|
|
Term
| Why are some fungi called dimorphic? |
|
Definition
| Bc they may exist in both a yeast and mold form |
|
|
Term
Give the basic characteristics of fungi:
respiration
metabolism
reproduction |
|
Definition
mostly aerobic respiration
heterotrophic metabolism
sexual (formation of spores) or asexual (mitosis) |
|
|
Term
| Compare teleomorph to anamorph. |
|
Definition
| teleomorphs produce sexual spores and anamorphs produce asexual spores |
|
|
Term
| What are the two types of asexual spores |
|
Definition
| sporangiospores and conidia |
|
|
Term
| What are the 5 classes of fungi. |
|
Definition
1) zygomycetes
2) basidiomycetes
3) archiascomycetes
4) hemiascomycetes
5) euascomycetes |
|
|
Term
| Describe suprficial mycoses. |
|
Definition
| infections limited to superficial surfaces of skin and hair; nondestructive |
|
|
Term
| Describe cutaneous mycoses |
|
Definition
| infections of keratinized layer of skin, hair and nails; elicit host response and become symptomatic |
|
|
Term
| Describe subcutaneous mycoses |
|
Definition
| infections at deeper layers of skin via traumatic inoculation |
|
|
Term
|
Definition
| infections caused by classic dimorphic fungal pathogens; primary infection in lung |
|
|
Term
| Define opportunistic mycoses |
|
Definition
| Infections attributable to fungi normally found as human commensals or in environment |
|
|
Term
| What are the two MOA of amphotericin B (polyene) as an antifungal? |
|
Definition
1) binds to ergosterol producing ion channels and leakage of intracellular constituents
2) direct membrane damage by generating oxidative reaction |
|
|
Term
| What is the MOA of azoles as an antifungal? |
|
Definition
| by inhibiting fungal cytochrome P450-dependent enzyme lanosterol 14-alpha-demethylase, which disrumpts membrane synthesis |
|
|
Term
| What are the two groups of azoles? |
|
Definition
|
|
Term
| What is the MOA of echinocandins as an antifungal? |
|
Definition
| inhibits synthesis of 1,3-beta-glucans which are important constituents of fungal cell wall |
|
|
Term
| What are the two groups of azoles? |
|
Definition
|
|
Term
| What is the MOA of echinocandins as an antifungal? |
|
Definition
| inhibits synthesis of 1,3-beta-glucans which are important constituents of fungal cell wall |
|
|
Term
| What is the MOA of flucytosine (antimetabolite) as an antifungal? |
|
Definition
| interferes with synthesis of DNA, RNA |
|
|
Term
| What is the MOA of allylamines as an antifungal? |
|
Definition
| inhibit the enzyme squalene epoxidase, which decreases ergosterol |
|
|
Term
| What is the MOA of griseofulvin as an antifungal? |
|
Definition
| interacts with MTs resulting in inhibition of mitosis |
|
|
Term
| Name four infections that are superficial mycoses. |
|
Definition
1) tinea versicolor
2) tinea negra
3) white piedra
4) black piedra |
|
|
Term
| What is the morphology of tinea versicolor? |
|
Definition
| clusters of spherical, thick-walled yeastlike cells; cream-colored colonies on culture |
|
|
Term
| What is the epidemiology of tinea versicolor? |
|
Definition
| most prevalent in tropical and subtropical regions; young adults |
|
|
Term
| What is clinical syndrome of tinea versicolor? |
|
Definition
| irregular, lesional patches of pityriasis versicolor on upper trunk |
|
|
Term
| What is lab diagnosis of tinea versicolor? |
|
Definition
| epidermal scales upon microscopic examination or yeastlike colonies with occasional hyphae in culture |
|
|
Term
| What is treatment for tinea versicolor? |
|
Definition
| topical azoles or selenium sulfide shampoo |
|
|
Term
| What is morphology of tinea negra? |
|
Definition
| dematiaceous, branched, hyphae with budding cells and black mold |
|
|
Term
| What is epidemiology of tinea negra |
|
Definition
| tropical or subtropical; children and young adults with higher incidence in females |
|
|
Term
| What are clinical syndromes of tinea negra |
|
Definition
| solitary, irregular, pigmented macule on palms or soles |
|
|
Term
| What is lab diagnosis of tinea negra? |
|
Definition
| two-celled cylindrical yeastlike cells on microscopic exam; toruloid hyphae on culture |
|
|
Term
| What is treatment of tinea negra? |
|
Definition
| topical therapy with azole creams and terbinafine |
|
|
Term
| Contrast white vs. black piedra |
|
Definition
| Both affect hair but white piedra presents as white to brown swelling along hair strand of groin and axillae; black piedra shows small, dark nodules surrounding hair shafts |
|
|
Term
| Why is infection with HSV inapparent at times? |
|
Definition
| establishes latent infection of the innervating ganglia |
|
|
Term
| What are the 3 consequences of primary infection? |
|
Definition
1) most will be asymptomatic
2) initial infection may be fully productive and symptomatic
3) virus establishes a latent infection |
|
|
Term
| What are two severe forms that HSV 1 presents in children? |
|
Definition
| gingivostomatitis or encephalitis |
|
|
Term
| What does it mean for the virus to establish a latent infection? |
|
Definition
| viral genome is largely quiescent and infectious virus is not produced |
|
|
Term
| Where do HSV 1 and 2 establish latency? |
|
Definition
| 1 in cervical ganglia and 2 in sacral ganglia |
|
|
Term
| Describe structure of HSV virion |
|
Definition
| enveloped and contains icosahedral capsid in which linear, ds DNA genome is born; envelope has typical lipid bilayer embedded by 10 viral glycoproteins organized into spikes; tegument is under envelope; further beneath is capsid, which is composed of 4 proteins organized into hexamers and pentamers |
|
|
Term
|
Definition
| largely amorphous, gelatinous matrix of at least 20 viral proteins |
|
|
Term
|
Definition
| 4 isomers exist; comprised of long unique sequence (UL) and short unique sequence (US), each flanked by its own inverted repeat |
|
|
Term
| Which cells does HSV infect? |
|
Definition
| polarized epithelial cells of orpharynx or genitalia and polarized neurons of trigeminal or sacral root ganglia |
|
|
Term
| What are the 3 membranes that HSV must adsorb through? |
|
Definition
1) apical membrane
2) axonal membrane
3) basolateral membrane |
|
|
Term
| What two parts does adsorption of HSV require? |
|
Definition
| recognition and attachment |
|
|
Term
| Which target cells allows HSV to adsorb in 1 step? |
|
Definition
| apical surface of polarized epithelial cells |
|
|
Term
| Which target cells allows HSV to adsorb in 2 steps? |
|
Definition
|
|
Term
| What receptors are involved with the HSV 2 step adsorption process? |
|
Definition
| heparan sulfate or chondroitin sulfate; HVEM, nectins and 3-O-sulfated heparan sulfate |
|
|
