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Define mycosis
a fungal infection
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Briefly describe yeasts and state how they reproduce asexually.
- unicellular, oval-shaped fungi
- facultative anaerobes
- reproduce by budding
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Name a yeast producing these structures - pseudohyphae, hyphae, blastoconidia (blastospores), and chlamydoconidia (chlamydospores)
Candida albicans
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pseudohyphae
filament-like structures
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blastoconidia
asexual spores
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chlamydoconidia
thick-walled survival spores
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Name 3 potentially pathogenic yeasts and state an infection each causes
- candida Albicans - vaginitis, thrush, balanitis
- cryptococcus neoformans - cryptococcal meningoencephalitis
- pneumocystis jiroveci - PCP (severe pneuomonia)
- Malassezia globosa - dandruff
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Define mold
multinucleated, filamentous fungi composed of hyphae
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Define hyphae
a branching tubular structure approximately 2-10 µm in diameter which is usually divided into cell-like units by crosswalls called septa
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Define mycelium
the total mass of hyphae
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Define vegetative mycelium
The portion of the mycelium that anchors the mold and absorbs nutrients
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Define aerial mycelium
the portion that produces asexual reproductive spores
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What are conidiospores
Spores borne externally on an aerial hypha
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What are macroconidia
a large usually multinucleate conidium of a fungus
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What are microconidia
a conidium of the smaller of two types produced by the same fungal species and often differing in shape
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What are sporangiospores
Spores borne in a sac or sporangium on an aerial hypha
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What are arthrospores
spores produced by fragmentation of a vegetative hypha
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Define dermatophyte
a group of molds that cause superficial mycoses of the hair, skin, and nails and utilize the protein keratin (that is found in hair, skin, and nails) as a nitrogen and energy source
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list 3 genera of dermatophytes
Microsporum, Trichophyton, and Epidermophyton
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name 3 dermatophytic infections
- tinea barbae (infection of the bearded areas of the face and neck)
- tinea faciei (infection of the skin of the face)
- tinea pedis (athlete's foot; infection of the soles of the feet and between the toes)
- tinea capitis (infection of the skin of the scalp, eyebrows, and eyelashes)
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Describe what is meant by the term "dimorphic fungus"
- exhibit two different growth forms
- Outside the body they grow as a mold, producing hyphae and asexual reproductive spores
- but in the body they grow in a non-mycelial yeast form.
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name 2 systemic infections caused by dimorphic fungi, and state how they are initially contracted
- coccidioidomycosis - southwestern US, contracted by inhalation of arthrospores
- histoplasmosis - Great lakes region + mississippi + ohio river, contracted by inhalation of macro/microconidia, grows as encapsulated yeast in lungs
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Name at least 3 fungal virulence factors that promote fungal colonization.
- compromised immune system
- capsules to resist phagocytic engulfment
- ability to adhere to host cells w adhesins
- some fungi are more resistant to phagocytic destruction
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Name at least 2 fungal virulence factors that damage the host.
- PAMPs binding to PRRs
- secretion of enzymes to digest cells
- secretion of mycotoxins
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Briefly describe 3 different ways antifungal chemotherapeutic agents may affect fungi and give an example of an antibiotic for each way.
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Briefly describe protozoa.
- unicellular, eukaryotic microorganisms
- lack a cell wall
- relatively few cause disease
- most inhabit soil and water
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Briefly describe 3 ways protozoans may reproduce asexually
- fission - one cell splits into two
- budding - pinches off parent cell
- schizogony - multiple fission of nucleus followed by segmentation of cytoplasm to form masses around nucleus
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Define trophozoite
the vegetative, reproducing, feeding form of a protozoan
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Define protozoan cyst
- dormant, protective form
- allows them to survive harsh environments
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Entamoeba histolytica
- moves by pseudopodia
- causes gastrointestinal infection
- transmitted by fecal-oral route
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Acanthamoeba
- move by pseudopodia
- causes infections of the eye, skin, and central nervous system
- enters through the eye or through contact lenses
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Giardia lamblia
- moves by flagella
- causes gastrointestinal infection
- transmitted by fecal-oral route
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Trichomonas vaginalis
- moves by flagella
- infects the vagina and male urinary tract
- transmitted by sexual contact
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans:. Trypanosoma brucei-gambiens
- moves by flagella
- causes African sleeping sickness
- transmitted by bite of an infected Tsetse fly
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Balantidium coli
- moves by means of cilia
- causes diarrhea-type infection called balantidiasis
- transmitted by fecal-oral route
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Plasmodium species
- not motile
- cause malaria
- transmitted by bite of an infected female Anopheles mosquito
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Toxoplasma gondii
- not motile
- causes toxoplasmosis
- contracted by inhaling or ingesting cysts from feces of infected domestic cats
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State a disease caused by each of the following protozoans and indicate their means of motility and how they are transmitted to humans: Cryptosporidium
- not motile
- causes a gastrointestinal infection called cryptosporidiosis
- transmitted by fecal-oral route
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State 2 living and 2 nonliving characteristics of viruses.
- living - reproduce in living host cells , can mutate
- nonliving - acellular, no metabolism
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List 3 criteria used to define a virus.
- vast majority of viruses contain only one tpe of nucleic acid - dna or rna but not both
- totally dependent on host cell for replication
- must assemble into complete viruses to go from one host cell to another
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Discuss why bacteria can be cultivated on synthetic media such as nutrient broth whereas viruses cannot.
- because they lack metaolic machinery of their own and they are totally dependent on their host cell for replication
- so they cannot be grown in synthetic culture media
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Define bacteriophage.
viruses that only affect bacteria
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Define mycophage
viruses that infect only fungi
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Define virophages
viruses that infect other viruses
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Compare the size of most viruses to that of bacteria.
- only 5-300 nm in size
- bacteria about 0.5-1.0 um
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List 4 shapes of viruses.
- helical - cylinder shaped capsid
- polyhedral - many sided shell/capsid
- enveloped - helical or polyhedral core surrounded by envelope
- binal - irregular shaped
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Describe what an animal virus consists of structurally.
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Define capsid
- aka core
- protein shell surrounding the genome
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Define capsomere
protein subunits that make up the capsid
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Define nucleocapsid.
- viruses that consist of no more than a genome surrounded by a capsid
- aka naked viruses
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Describe how most animal viruses obtain their envelope.
dervied from host cell membranes by a process called budding
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State why some bacteriophages are more complex than typical polyhedral or helical viruses
may possess a unique tail structure
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State what criteria are used in viral classification.
- single vs double stranded
- DNA vs RNA
- naked vs enveloped
- shape of capsid
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Regarding the naming of enzymes involved in the replication of viral nucleic acid, state what the "dependent" part of the name refers to and what the "polymerase" part of the name refers to.
- dependent - refers to what type of nucleic acid is being copied
- polymerase - refers to the type of nucleic acid being synthesized
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Define viroid and name an infection caused by a viroid.
- small, circular, single-stranded molecules of infectious RNA that cause several plant diseases
- ex - cucumber pale fruit
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Define prion
infectious protein particles responsible for a group of transmissible and/or inherited neurodegenerative diseases bc of prion protein misfolding
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Name 3 protein misfolding diseases that appear to be initiated by prions
- alzheimer's
- huntington's
- parkinson's
- ALS
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describe how an enveloped virus accomplishes each of the steps of the productive life cycle
- attachment sites on the viral envelope bind to corresponding host cell receptors
- enter the cell by endocytosis or by fusing the viral envelope with the host membrane
- viral envelope fuses with the endocytic vesicle and the viral nucleocapsid enters the host cell
- during maturation, envelope glycoproteins are transported to the host cell's membrane and the capsid assembles around the genome
- released by host cell lysis or budding
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describe how a naked virus accomplishes each of the steps of the productive life cycle
- attachment sites on the viral capsid bind to corresponding host cell receptors
- enter the cell by rearranging capsid proteins to pass through the membrane or by receptor-mediated endocytosis
- during maturation, the capsid assembles around the viral genome
- released by host cell lysis
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State the major difference between the productive life cycle of animal viruses and the latent life cycle.
the viruses can remain latent within infected host cells for long periods of time without replication or causing harm
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Define provirus
an animal virus that has inserted its DNA into the chromosomes of the host cell
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Name 3 herpes viruses that may have a latent cycle, state in what cell types they become latent, and name the diseases each cause
- HSV-1 -- latent in the body of sensory neurons, causes fever blisters/oral herpes
- HSV-2 -- latent in the body of sensory neurons, causes genital herpes
- EBV -- latent in b-lymphocytes, causes mono
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Name 3 types of cells HIV primarily infects and briefly explain why
- T4-helper lymphocytes
- monocytes
- macrophages
- dendritic cells
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State the median incubation period for AIDS
around 10 years
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Briefly describe what marks the progression to AIDS
marked by a viral load that progressively increases in number while the immune system weakens as a result of the destruction of increasing numbers of T4-lymphocytes and the inability of the body to continually replace these destroyed cells.
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Briefly describe early or acute HIV infection
the virus primarily infects and destroys memory T4-lymphocytes which express the chemokine receptor CCR5
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Briefly describe chronic HIV infection
- Characterized by viral dissemination, viremia, and induction of adaptive immune responses
- A steady state-infection generally persists where T4-lymphocyte death and T4-lymphocyte replacement by the body are in equilibrium
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Describe how certain viruses may contribute to the development of tumors by altering proto-oncogenes or tumor-suppressor genes.
- muttions that increase the activities of proto-oncogenes to create oncogenes
- or decrease the activities of tumor supressor genes can lead to growth of tumors
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Name 3 viruses that have been implicated in human cancers.
- hepatitis B virus (HBV)
- heptatitis C virus (HCV)
- human papilloma viruses (HPV)
- epstein-barr virus (EBV)
- human immunodeficiency virus (HIV)
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Name the 2 types of bacteriophage life cycles and state what the bacteriophage capable of each is called.
- lytic life cycle - lytic bacteriophages
- lysogenic life cycyle - temperate phages
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Describe the steps involved in the lytic life cycle of bacteriophages.
- adsorption (attach to host bacterium)
- penetration (injects genome into cytoplasm)
- replication (uses bacterial machinery to replicate genome)
- maturation (phage parts assemble around genome)
- release (lysozyme breaks down bacterial cell wall causing lysis)
- reinfection
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What is a lytic bacteriophage
bacteriophages that replicate through the lytic life cycle
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What is the eclipse period
period during the viral life cycle when no intact viruses can be seen inside the host cell
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Describe the lysogenic life cycle of temperate phages (including spontaneous induction).
- adsoption (attaches to host bacterium)
- penetration (injects genome into cytoplasm)
- early repliction (phage genome replicates and components are produced)
- late replication (more production of components)
- maturation (phage components assemble)
- release (lysozyme breaks down cell wall OR phage instead its genome into the bacterial nucleoid to become a prophage)
- rare rpontaneous induction (phage replicates via lytic life cycle)
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What is a temperate phage
bacteriphages capable of a lysogenic life cycle
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Define lysogen
the host bacterium
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Define prophage
a bacteriophage that has integrated its DNA into the chromosome of host bacterium
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Briefly describe at least 4 ways viruses can damage infected host cells.
- inhibiting DNA/RNA/protein synthesis
- causing nicks or breaks in host cell's chromosomes
- stimulating body to release inflammatory cytokines/chemokines
- depleting host cell of matierals essential for life
- causing cytolysis of infected host cell
- causing autoimmune response
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Briefly describe at least 3 different ways viruses can evade host immune defenses
- can undergo antigenic drift and antigenic shift
- mutation produces viral variants
- block CTLs from recognizing infected cell and killing it
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Describe the process of lysogenic conversion
- the added genetic info from DNA of a prophage enables bacterium to possess new genetic traits
- new genetic info allows for coding of protein exotoxin or other virulence factors
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give 2 examples of exotoxins that result from lysogenic conversion
- Streptococcal pyrogenic exotonic (Spe)
- diptheria exotoxin
- neurotoxin made by Clostridium botulinum
- cholera extoxoin
- shiga toxins by E. coli
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State why antibiotics are of no use against viruses and what we must rely on to control viruses.
- because viruses lack the structures and metabolic processes that antibiotics affect
- viruses are also not bacteria
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State what viruses the following antiviral agents are used against: amantadine, rimantidine, zanamivar, and oseltamivir
against influenza A viruses
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State what viruses the following antiviral agents are used against: acyclovir, famciclovir, penciclovir, and valacyclovir
- herpes simplex viruses (HSV)
- varicella zoster viruses (VZV)
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State what viruses the following antiviral agents are used against: foscarnet, gancyclovir, cidofovir, valganciclovir, and fomivirsen
severe cytomegalovirus (CMV)
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State what viruses the following antiviral agents are used against: AZT (ZDV), didanosine, zalcitabine, stavudine, lamivudine, emtricitabine, tenofovir, and abacavir
HIV infection and AIDS
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State what viruses the following antiviral agents are used against: nevirapine, delavirdine, and efavirenz
HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs)
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State what viruses the following antiviral agents are used against: saquinavir, ritonavir, idinavir, nelfinavir, amprenavir, atazanavir, fosamprenavir, ritonavir
protease inhibitors
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State what the viruses the following antiviral agents are used against: telaprevir, boceprevir, simeprevir, sofosbuvir
hepatitis C
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Compare how the following drugs exhibit their antiviral action against HIV -- nucleoside reverse transcriptase inhibitors
- a nucleotide analog that stops DNA synthesis
- results in an incomplete provirous
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Compare how the following drugs exhibit their antiviral action against HIV -- protease inhibitors
prevent proteases from cleaving the long gag-pol polyprotein, which is essential to the structure of the HIV
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Compare how the following drugs exhibit their antiviral action against HIV -- entry inhibitors
- interfere with entry of HIV into cells
- block binding of gp120 to host chemokine receptor 5
- block fusion of viral envelope with host membrane
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Describe and give an example of an acute viral infection
- relatively short duration with rapid recovery
- cold viruses, influenza viruses, gastrointestinal infections
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Describe and give an example of a late complication following an acute infection
- viruses are continually present in the body
- SSPE (subacute sclerosing panencephalitis) following acute measles infection
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Describe and give an example of a latent viral infection
- virus remains in equilibrium with the host for long periods of time before symptoms appear again, but actual viruses cannot be detected until disease is reactivated
- fever blisters, genital herpes, chickenpox-shingles
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Describe and give an example of a chronic viral infection
- virus can be demonstrated in the body at all times and the disease may be present or absent for an extended period of time
- hepatitis B, hepatitis C
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Describe and give an example of a slow viral infection
- infectious agents gradually increase in number over a very long period of time during which no significant symptoms are seen
- AIDS
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