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Micro 2nd Exam
Dr. Mittak's 2nd Microbiology Midterm
| Question | Answer |
|---|---|
| More than 30 new diseases have been identified in the past 30 years, name 4. | Legionnaire's disease AIDS Hepatitis Nipah virus infection |
| 4 more new diseases | Hemorrhagic fevers SARS Creutzfeld-Jacob Disease (mad cow) Avian flu |
| What are 2 of the biggest re-emerging diseases after being dormant? | TB Cholera |
| What are some reasons why infectious diseases are re-emerging? | Antibiotic resistance Falling living standards, infrastructure decline in some countries |
| Define emerging infectious diseases. | Those whose incidence has increased over the past 30 years. Some diseases never seen before and some documented before with unknown etiology. |
| What are some ongoing causes of emerging infectious diseases? | Global urbanization Increase in population density Poverty Social upheaval Travel Long distance trade Technology development Land clearance Climate change |
| What are 2 diseases encountered as a result of humans encroaching on uncultivated environments? | Hanta virus Dengue fever |
| What has caused the emergence of infections from farm animals to humans and what are 3 of these infections? | Population growth has increased pressure to produce more meat. Salmonella species Mad cow disease E. coli |
| In what 2 ways does changing human behavior patterns and changing ecology contribute to emergence of infectious disease? | Increased opportunity for animal-to-human transfer b/c greater exposure Increased opportunity for transmission from human to human |
| What occurs with re-assortment? | Genetic changes in pathogens; e.g. avian influenza |
| What must a pathogen do to replicate successfully in a human host? (2) | 1. Must adapt in such a way that it can replicate in human cells 2. Must be able to configure itself so that it can be easily transmitted from one human to another. |
| When did SARS become readily transmissible? Where was the first documented case and how is it transmitted? | 1990s Mainland China droplet aerosol and fomites on respiratory mucosal epithelium |
| Where does SARS infect and what are some symptoms? | Lower respiratory tract fever, malaise, and lymphopenia of T cells |
| What causes West Nile Virus, how is it transmitted, what is it a member of and who are the primary hosts? | Arbovirus Saliva of mosquitoes transmitted through bites Japanese encephalitis group Birds, spread from bird to bird by mosquitoes |
| What causes a person with West Nile Virus to become symptomatic and what are some of those symptoms? | If the infection causes an invasive neurological disease called West Nile Fever fever, headache, myalgia and anorexia. can cause profound fatigue, myocarditis, pancreatitis, and hepatitis |
| What diseases are classified as VHF's? Which are fatal and what type of virus are they? | Ebola, Marburg, and Yellow fever Ebola and Marburg fatal Single-stranded enveloped RNA viruses |
| VHF's transmitted how and what are some symptoms? | Arthropod and rodent vectors and all can be transmitted between humans fever, bleeding and circulatory shock |
| What is the causative agent for tuberculosis? | Mycobacterium tuberculosis |
| What are possible causes for the increase in incidence of TB? | HIV/AIDS Increased poverty, IV drug abuse, homelessness Increased immigration of those infected Increased elderly population Failure of patients to complete antibiotic treatments |
| What does the RNA virus of influenza have and what is it capable of? | Contains 8 seperate segments of nucleic acid High mutation rates that change characteristics 2 surface glycoproteins hemagglutinin and neuraminicase that occur in several subtypes |
| Why is avian flu potentially the most devastating re-emerging disease in the world? | Can be transmitted from animal to humans Mutates rapidly Capable of spreading at an alarming rate More deadly than any other influenza Could be 10x more dangerous than Spanish flu Possible 50% mortality rate Resistant to amantadine and rimantadine |
| What are prions and diseases of them are called? | Infectious proteins Transmissible spongiform encephalopathies |
| Prions are abnormally folded PrP^sc. Where do they aggregate and what can they do there? | Fibrous structures of the brain (plaque) Disrupt cell membrane -> cell death Convert normal prions to abnormal prions (proteins folding incorrectly) |
| Why are prions practically indestructible? | Can withstand cooking Can withstand autoclaving Resistant to strong alkali tx Resistant to disinfectants Can survive in soil for years |
| What do prions produce and what is it? | Transmissible spongiform encephalitis (TSE) Neurodegenerative disease Can affect cattle and humans Not test for it in the living No tx and no cure |
| Symptoms of TSE? | Lack of coordination Staggering Slurred speech Dramatic mood swings Paralysis Death w/in 1 year of symptom onset |
| Mad cow disease (TSE) infection has been attributed to what? | Sheep brain supplement in cattle feed. |
| What are some biological characteristics of TSE? | Long incubation time Plaque deposits in the brain No antibody response No inflammatory response since self folds incorrectly |
| 5 forms of TSE seen in humans? | *1. Kuru (cannibalism) 2. Creutzfeld-Jacob disease (CJD) *3. Variant CJD 4. Gerstmann-Straussler-Scheinker syndrome (GSS) 5. Fatal Familial Insomnia (FFI) (1 and 3 starred for importance) |
| What does the bacterial cell wall protect against? | Osmotic pressure changes Other environmental stresses |
| What is the primary structure of the bacterial cell wall and how many of them are found in a cell wall? | Peptidoglycans 2!! N-acetyl glucosamine N-acetyl muramic acid (Repeating molecules held together with peptide chains) |
| What are some difference between gram-negative and gram-positive cell walls? | Gram-positive cell wall is rich in peptidoglycan with multiple layers of meshwork Gram-negative cell wall contains very little peptidoglycan. |
| What 3 components of bacterial cell walls are unique to gram-positive bacteria? | Teichoic acid (stabilizes cross linkages like "mortar") M protein (aids in adherence) Mycolic acid (Found only in mycobacterium) |
| What are 2 forms of teichoic acid? | 1. Wall teichoic acids go part way through the wall 2. Lipoteichoic acids go completely through a wall and link to the plasma membrane. Both forms protrude above the wall giving cell a negative charge which stains nicely. |
| What are 4 things we should know about M protein? | 1. Virulence factor 2. Protrudes from cell wall 3. Required for infection 4. Highly susceptible to mutations |
| Name 4 things that should be known about mycolic acid? | 1. found in mycobacterium species 2. Consists of a waxy lipid incorporated into cell wall 3. Makes cells extremely resistant to environmental stress 4. Acts as a barrier against antibiotics and host defenses |
| Gram-negative cell walls have a unique outer membrane known as what and what does it do? | Lipopolysaccharide layer (LPS) Composed of lipids, proteins and polysaccharides. Fastens the outer membrane to the peptidoglycan layer. It serves as a major barrier to the outside world for the gram-negative cell. |
| The outer layer of a gram-negative bacterial cell wall functions as an _________ with what 2 parts? | Endotoxin Lipid A O polysaccharide |
| What does lipid A do and when is it released? | Anchors the LPS part of the outer layer Released when cell dies |
| What are O polysaccharides? (4) | 1. Carbohydrate chains that are part of the outer layer 2. Variable from one bacterial species to another 3. Recognized by the adaptive immune response 4. Sometimes used as a diagnostic marker (e.g. E. coli 0157:H7 is designated by O polysaccharide 157 |
| How many structures can be found outside of a bacterial cell wall? | 5, no bacterium has all 5 at the same time. |
| 3 structures found outside the bacterial cell wall that are involved with adherence (staying in) are? | 1. Glycocalyx 2. Fimbriae 3. Pili |
| 2 structures found outside the bacterial cell wall are primarily used for motility, what are they? | 1. Flagella 2. Axial filament |
| What is the glycocalyx composed of, where is it produced and what does it provide? | A sticky substance made up of polypeptides, polysaccharides or both. It is produced in the cytoplasm and secreted to the outer part of the cell wall. Provides protective element agains environmental stress and can be used for nutrition |
| If the glycocalyx is loosely attached to the wall it is called a _____________; if adhered tightly it is called a _______. What do these variations do for the organism? | Slime layer Capsule Adherence capability to the organism |
| What requirement for infection is the glycocalyx used for and in what regions of the body? | Adherence Respiratory and Urinary tract infections |
| What are 4 clinical significances of the glycocalyx? (1 slime layer, 3 capsule form) | 1. Slime layer is associated with some forms of dental decay Capsule: 1. Inhibits phagocytosis 2. Many not infectious w/o a capsule 3. Capsule genes can be transferred b/w organisms |
| What are fimbriae and pili found on, what are they composed of? | Gram-negative organisms; pilin protein subunits |
| In what 2 ways can pili give bacteria motility and what are pili involved in developing? | 1. twitching or gliding movements 2. through extension and retraction of the pili Involved in the development of biofilms (mouth and teeth) |
| Pili can facilitate what and this can be used for? | Transfer of genetic material from one bacterial cell to another; Antibiotic resistance Toxin production Defense against host defenses |
| What are axial filaments, what do they do and what are they used for? | Flagellum like structures found on spirochetes; Wrap around bacterial cell and are confined to the space b/w plasma membrane and cell wall; Used for motility and cause the entire organism to rotate like a corkscrew. |
| 2 Clinically significant things of axial filaments? | Corkscrew motion gives bacterium ability to bore through tissue; They allow organisms to get into the blood as well as other tissues |
| 4 flagella configurations? | 1. monotrichous-1 flagellum located at the end of the cell 2. Amphitrichous-2 flagella, one at each end of the cell 3. Lophotrichous-2 or more flagella located at the same end of the cell 4. Peritrichous-flagella surround entire cell |
| What does the flagella allowing movement allow for the bacteria? | Opportunistic infections Escape from host defenses Systemic infection |
| What are the 6 major structures found inside a bacterial cell wall? | Plasma membrane Nuclear region Plasmids Ribosomes Inclusion bodies Endospores |
| What is the plasma membrane, what does it do and what is it involved in? | A delicate, flexible structure; Surrounds internal cell matrix and organelles; Provides a barrier b/w the inside and outside of the cell; Involved in: DNA replication, Generation of energy, Transport and secretion |
| The plasma membrane is a primary target for ___________ and damage to the membrane can do what? | antibiotics; Inhibit DNA replication, destroy ability to produce energy, cause loss of membrane integrity and destruction of the cell. |
| The region where DNA is located in bacteria is called the ______. | nuclear region; 1 chromosome which contains all the genetic info. required by the organism. |
| What are plasmids, what do they carry and how can they be transferred? | Extra-chromosomal pieces of DNA seperate from main DNA structure; Carry genes for toxins and resistance to antibiotics; through pili |
| What protein forming organelle is a major target for antibiotics? | ribosomes |
| How and when are endospores formed and the process is restricted to? | Sporulation and form when bacterium is exposed to great environmental stress; Gram-positive (1 exception coxiella burnetti) |
| What 3 things can endospores do for a bacterial cell? | 1. confer a type of dormancy 2. Extremely resistant to heat, desiccation, toxic chemicals, UV irradiation and antibiotics 3. Bacteria can survive for extraordinary lengths of time in the endospore state |
| Name 3 things that are of clinical significance of sporogenesis | 1. If bacterium is pathogenic when it goes dormant, it will be pathogenic when emerges 2. Endospores are resistant to almost all disinfectants, antiseptics and antibiotics 3. Resistant to heat and can cause problems for the food industry, e.g. botulism |
| Each division of a bacteria is called a ___________ the time b/w divisions is called _______. | generation generation time |
| The shorter the generation time of bacteria the faster what happens? | Number of bacteria increases in the host. |
| What are the 3 temperature ranges for bacterial growth? | 1. Psychrophiles-grow at cold temperatures 2. Mesophiles-grow at moderate temperatures 3. Thermophiles-grow at high temperatures |
| The optimum growth temperature is what? | temperature at which the highest rate of growth occurs |
| What pH do most bacteria prefer? What do you call bacteria that grow at a low pH and is helicobacter pylori one of them? | 7.0 acidophiles no, it grows at low pH but forms a buffer for itself |
| Why do some bacteria die in the presence of oxygen? | Production of the superoxide free radical that steals electrons and kills the organism |
| What are the 2 types of bacteria that grow in the presence of oxygen? What do both types produce? | Aerobes: require oxygen for growth Facultative anaerobes can grow with or w/o oxygen An enzyme called superoxide dismutase that converts free radical to molecular oxygen and peroxide. |
| What 2 enzymes do bacteria produce to deal with peroxide? | 1. Catalase - converts peroxide to water and oxygen 2. Peroxidase - converts peroxide to water |
| How does pH negatively affect protein structure? | Excess of H ions causes bonds to break, changing 3D structure, these changes destroy protein function |
| How does osmotic pressure affect bacteria? | It is the pressure exerted on bacteria by their environment. It can inhibit growth. |
| What is a halophilic organism and what 3 categories can they be divided into? | A bacteria that thrives in high salt environments; 1. Obligate - requiring high salt [] 2. Extreme - requiring very high levels of salt 3. Facultative - can grow either w/ or w/o high salt levels |
| What are the 3 major bacteria categories based on oxygen use? | 1. Obligate aerobes - require oxygen for growth 2. Obligate anaerobes - cannot survive in the presence of oxygen 3. Facultative anaerobes - can grow w/ or w/o oxygen |
| What are the 2 smaller categories of bacteria based on oxygen use? | 1. Aerotolerant - grows in oxygen but does not use it in metabolism 2. Micro aerophile - requires only low levels of oxygen for growth |
| What does the medium sodium thioglycolate do and where do the organisms grow? | Forms an oxygen gradient during growth Aerobic organisms grow at the top Anaerobic organisms grow at the bottom Facultative anaerobes grow throughout the medium |
| What does a GasPak Jar do and what 2 types of organisms can grow in this medium? | Provides an oxygen-free environment; only obligate and facultative anaerobes can grow via this method |
| What are selective and differential media? | Selective is one that contains ingredients that prohibit the growth of some organisms while fostering the growth of others. Differential medium is one that contains ingredients that can differentiate between organisms. |
| What are the 4 stages of bacteria growth? | 1. Lag phase 2. Log phase 3. Stationary phase 4. Death phase |
| What is the lag phase of bacterial growth? | Bacteria are adjusting to their environment, varies depending on the organism and the environment. |
| What is the log phase of bacterial growth? | The number of bacteria doubles exponentially. This phase lasts only as long as a suitable level of nutrients are available. Bacteria are the most metabolically active and most susceptible to antibiotics in this phase. |
| Why are some bacteria considered fastidious and what is a disadvantage to their growth speed? | Require a large number of growth factors rather than just 1 or 2. They grow very slowly and can be missed diagnostically giving false negatives. |
| What is the stationary phase of bacterial growth? | The number of cells dividing is equal to the number dying b/c of decreasing availability of nutrients. |
| What is the death phase of bacterial growth? | Logarithmic decline phase. A continuous decline in the number of dividing cells caused by exhaustion of the nutrient supply and by a build-up of metabolic waste. |
| More than 80% of infectious diseases are caused by _________. | Viruses, which can "help" bacterial/fungal infections be worse |
| Viruses are defined as ______________ and what is their goal? | Obligate intracellular parasites (they cannot live outside a cellular host) A productive infection |
| What 3 types of cells can viruses infect? | Bacteria (called bacteriophages) Plant cells Animal cells They are specific for a certain cell type |
| What is an intact viral particle called? Its nucleic acid is surrounded by a protein coat called _______ which is made up of what? | Virion Capsid Capsomeres |
| There are _____ types of viruses which are... | 2 DNA RNA |
| Capsomeres bond together and give the capsid _________ and what are the 2 types? | Structural symmetry Helical and Icosahedral |
| What are the 2 shapes of helical viruses? | Rod - straight and relatively rigid Filamentous - flexible, curved or coiled |
| The extrusions on a helical virus are ________. Which releases and which attaches? | proteins Neuraminidase releases and Hemagglutinin attaches |
| Icosahedral viruses shape is derived from __________ that make up the capsid and has how many points of symmetry? | 20 triangular faces 12 points of symmetry |
| What are the 2 types of icosahedral viruses? | Simple and Complex |
| Many viruses that infect humans and animals are _________ which form when what happens? | enveloped; Form when viral glycoproteins and oligosaccharides associate with the plasma membrane of the host cell. Envelopes increase virulence |
| What do all viral envelopes have? | Phosphlipid bilayer |
| In what 4 ways do viral envelopes vary? | Size, morphology, complexity, composition |
| What can glycoproteins in a viral envelope form and how can they be used? | Spikes or other structures on the outside of the virion that can be used to attach to a host cell. |
| What role does genome packaging have with viruses and what 3 ways are they packaged? | Role in the infection; 1. Directly in the capsid 2. Enclosed in special proteins 3. Enclosed in proteins from the host cell |
| What occurs with a lytic infection? | The host cells fill with virions and bursts. -> cell death (get in, spread and get out causing an inflam. response) |
| What occurs with a lysogenic infection? | AKA latent infection Viral genome becomes incorporated into the host cell's DNA. It can remain this way for some time, the host cell lives. |
| What are the 6 steps in a lytic infection? | Attachment Penetration Uncoating Biosynthesis Maturation Release |
| When does lytic attachment occur? | When a virion binds to specific receptors on a host cell. Some viruses require a co-receptor |
| What must a virus do after it has attached? | Gain entry into a host cell, it must also uncoat or remove the capsid. |
| In what three places can capsid uncoating occur? | 1. At the plasma membrane 2. In the cytoplasm 3. At the nuclear membrane |
| Biosynthesis of new viral components can be complex, viral genomes are either ______ or ______. What does it use to make copies of itself? | DNA or RNA Uses host cells proteins to make copies of itself |
| What is involved in viral maturation and what are the 2 steps? | Movement of newly made viral components to specific sites in the host cell. 1. Intracellular trafficking 2. Assembly (take over protein synthesis making new capsids) |
| In what 2 ways can virions be released from the host cell? | Lysis (rupture, instant immune response) Budding (pieces break off but not as violent of a response) |
| Non-enveloped viruses use _________ causing _______ of the host cell. | lysis; death (fast) |
| Enveloped viruses use ________ which allows the host cell to ____. | budding; live for a while (takes longer) |
| What can viruses use to spread from cell to cell? | Tight junctions Forming syncytia which allow movement through the body w/o immune system exposure. |
| Some viruses produce ___________ that confuse and distract host defenses. Others incorporate host proteins as a __________. | decoy virions camouflage |
| What are the most common plant pathogens? What causes human mycoses (2)? | Fungi Fungal pathogens and opportunistic pathogens |
| Where can a true or primary fungal pathogen invade and grow? | A healthy, uncompromised host |
| What is a surprising fungal adaptation to survival? | The ability to switch from hyphal cells to yeast cells. |
| What is thermal dimorphism? | Fungi grows as mold at 30C and as yeast at 37C |
| An opportunistic pathogen can only infect someone who has? | Impaired defenses Vary from superficial colonization to potentially fatal systemic disease |
| Why are opportunistic fungal pathogens are a emerging medical concern? | Account for 10% of all nosocomial infections and dermatophytes may be undergoing transformation into true pathogens (smarter) |
| What are the 4 most common opportunistic fungi? | 1. Candida 2. Aspergillus 3. Cryptococcus 4. Zygomycota species |
| Most fungal pathogens do not require what and are not __________? | A host to complete their life cycle; communicable |
| True fungal pathogens are distributed in a predictable _________. | Pattern - climate, soil |
| Dermatophytes are the most prevalent _________ and cases can go un- or mis-diagnosed and can be what 4 types of infections? | Mycotic pathogens; Systemic, subcutaneous, cutaneous or superficial infections |
| What are 3 portals of entry mycoses use? | 1. Primary mycoses - respiratory portal; inhaled spores 2. Subcutaneous - inoculated skin; trauma 3. Cutaneous and superficial - contamination of skin surface |
| Mycoses have what virulence factors? (5) | thermal dimorphism, toxin production, capsules and adhesion factors, hydrolytic enzymes, inflammatory stimulants |
| What antifungal defenses do humans have? | The barriers and respiratory cilia. Most important defenses are cell-mediated immunity, phagocytosis and inflammation. Long-term immunity can only develop for some. |
| What must be done to diagnose mycotic infections? | Microscopic examination of stained specimens, culturing in selective and enriched media and specific biochemical and serological tests |
| What are some ways of controlling mycotic infections? | IV amphotericin B, flycytosine, azoles and nystatin. Surgical removal of damaged tissues. Prevention is limited to masks and protective clothing to reduce spore contact. |
| What are 4 systemic infections by true pathogens? | 1. Histoplasma capsulatum 2. Coccidioides immitis 3. Blastomyces dermatitidis 4. Paracoccidioides brasiliensis All can and will kill |
| What is the most common true pathogen, what does it cause and what are some of its features? | Histoplasma capsulatum; causes histoplasmosis Dimorphic, distributed worldwide but most common in eastern and central U.S. Grows in moist soil high in N content. Can become systemic affecting multiple organs. Tx: Amphotericin B, ketoconazole |
| Coccidioides immitis causes ___________, what is its distinctive morphology? | coccidioidomycosis Blocklike arthroconidia in the free-living stage and spherules containing endospores in the lungs. |
| Where does coccidioidomycosis live, what does it do and what is a treatment? | Alkaline soils in semiarid, hot climates, is endemic to SW U.S. Arthrospores inhaled from dust, creates spherules and nodules in the lungs. Tx: amphotericin B |
| What does blastomyces dermatitidis cause? | Blastomycosis |
| Blastomycosis species live where and what symptoms are there? Treatment? | It is dimorphic. In soil of large section of the midwestern and southeastern U.S. Converts to yeasts which multiply in lungs, cough and fever result. If chronic, cutaneous, bone and nervous system complications result. Tx: Amphotericin B |
| Where is paracoccidiomycosis distributed? What does it cause and what are treatments? | Central and South America (toward equator). Lung infection occurs through inhalation or inoculation of spores. Tx: ketoconazole, amphotericin B, sulfa drugs |
| What are 3 subcutaneous mycoses? | Lymphocutaneous sporotrichosis Chromoblastomycosis Mycetoma |
| Sporotrichosis (AKA?) is found where, infects what, and can spread where? | Rose-gardener's disease Decomposes plant matter in soil, infects appendages and lungs and lymphocutaneous variety occurs when contaminated plant matter penetrates the skin and the pathogen forms a nodule which spreads to nearby lymph nodes. |
| How is chromoblastomycosis characterized? What are its etiologic agents and what does it produce? | Highly visible colorful lesions; soil saprobes with dark pigmented mycelia and spores. Produces large, thick, yeastlike bodies, sclerotic cells. |
| What is mycetoma? | When soil microbes are accidentally implanted into the skin. |
| What does mycetoma cause and what causes it? | Progressive tumorlike disease of the hand or foot due to chronic fungal infection; may lead to amputation to stop spread. Caused by pseudallescheria or madurella. |
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