Microbiology Final

Created by dourada 

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239 terms

viruses

-non-living infectious particles
-obligate intracellular parasites

virus size

20-450 nanometers
(need an electron microscope to see them, however you can see the damage they cause to an infected cell with a light microscope)

what is an envelope

lipoprotein layer that is modified piece of the host's cell membrane
-also frequently covered by glycoproteins

what do the glycoproteins on envelope do

form spike like projections that are used for attachment to cellular receptors
-they are also antigenic

if virus doesn't have a membrane what is it called

naked nucleocapsid

how do envelopes affect viral susceptibility

-confers a level of instability
-more susceptible to heat, detergents and lipid solvents such as alcohol

what is a capsid

protein shell that surrounds the nucleic acid strand of virus

what is name of nucleic acid and capsid together

nucleocapsid

what are the identical building blocks of capsids

capsomers and protomers

what are capsomers and protomers

clusters of small protein or polypeptide molecules

how do capsomers adn protomers make a capsid

they spontaneously self-assemble

what is difference between capsomers and protomers

capsomers-more complex and antigenic (icosahedrons)
protomers-antigenic and more simple
(helical)

what are the two types of capsids

helical
icosahedron

helical capsids

-rod shaped polypeptides called protomers
-hydrogen bond together and to nucleic acid
-form series of hollow discs (bracelet)
-linked in continuous helix - nucleic acid is wound in

can helical capsids be empty

because of arrangement they are incapable of producing an empty capsid

icosahedron

-3D, 20 sided polygon, 12 evenly spaced corners
-no bonding between capsomer and nucleic acid
-use at least 2 different forms of capsomers
-many associate with envelopes

can icosahedrons form empty capsids

yes because no direct bonding b/t capsomer and nucleic acid

what is advantage of structure based on identical protein subunits

-reduction of genetic information needed to reproduce it
-promotes self-assembly
-no energy or enzymes are required to form the viral capsid

functions of envelope and capsid

-protection from acidic and enzymatic fxs of the host
-attachment to host cell
-antigenic

complex viruses

atypical viruses that are more intricate in structure than the helical or icosahedron

poxviruse

-very large
-nucleic acid core
-lack regular capsid->just several layers of lipoproteins and coarse surface fibrils
(primitive membrane)

bacteriophages

-polyhedral head
-helical tail
-fibers for attachment to host cell

defective

-viral nucleic acid and proteins
-cannot replicate without a helper virus
(during course of many human viruses more defective than infectious particles are made)

pseudovirions

-contain host cell DNA rather than viral DNA

viroids

-single molecule of circular RNA
-without protein coat or envelope
-genetic material does not code for any proteins
-replication methodology not understood
-assoc w/ plant diseases-no known human infections

nucleic acids

-RNA or DNA
-number of genes: 4-400
-single strand or double strand

DNA viruses

Parvovirus
Papovirus
adenovirus
hepadnavirus
poxvirus
herpesvirus

parvovirus

-DNA
i.e. B19 virus

papovirus

-DNA
i.e. JC virus, BK virus, human papilomavirus

adenovirus

-DNA
i.e. viral forms of pharyngitis, upper and lower respiratory tract disease

hepadnavirus

-DNA
i.e. hepatitis B

poxvirus

-DNA
i.e. small pox virus

herpesvirus

-DNA
i.e. herpes simplex 1 and 2, varicella-zoster, cytomegalovirus, and Epstein-Barr virus

RNA viruses

picornavirus
calicivirus
reovirus
flavivirus
togavirus
retrovirus
orthomyxovirus
paramyxovirus
rhabdovirus
filovirus
coronavirus
arenavirus
bunyvirus

positive polarity

viral RNA has same make up as cellular mRNA
i.e. picorna, calici, flavi, toga, retro, corona

negative polarity

viral RNA has mirror image of cellular mRNA
i.e. orthomyxo, paramyxo, rhabdo, filo, arena, buny

positive polarity, non-segmented

picorna
calici
flavi
toga
corona

negative polarity segmented

orthomyxo

negative polarity non-segmented

paramyxo
rhabdo
filo

segmented

reo, orthomyxo

non-segmented

picorna,
calici,
flavi,
toga,
corona,
paramyxo,
rhabdo,
filo

single stranded linear

picorna, calici, flavi, toga, retro, orthomyxo, paramyxo, rhabdo, filo, corona

single stranded circular

arena, buny

double stranded

reovirus

Picornavirus

-enteroviruses-i.e . poliovirus, coxsackievirus, echovirus, and hepatitis A
-Rhinovirus-common cold
+NS

Calicivirus

i.e. Norwalk virus, and Hepatitis E
+NS

Reovirus

i.e. rotavirus
S
double stranded

Flavivirus

i.e. yellow fever, dengue virus, and st. louis and Japanese encephalitis virus
+NS

Togavirus

i.e. alpha virus (encephalitis) and rubvirus (rubella)
+NS

Retrovirus

oncovirus (sarcoma and leukemia viruses), lentivirus (HIV and certain animal pathogens)
+

Orthomyxovirus

i.e. influenza virus
-S

Paramyxovirus

i.e. measles, mumps, parainfluenza, and respiratory syncytial viruses
-NS

Rhabdovirus

i.e. rabies
-NS

filovirus

i.e. ebola and Marburg virus
-NS

Coronavirus

i.e. respiratory tract infections (common cold)
+NS

Arenavirus

i.e. lassa fever virus and lymphocytic choriomeningitis virus
- (SSC)

Bunyvirus

i.e. encephalitis and Korean hemorrhagic fever
- (SSC)

Eclipse period

from the time of initial entry to the time of the assembly of the first progeny virion

Time of most eclipse periods for human viruses

1-20 hours

Latent period

time from the onset of the infection to the appearance of the virus

Cytopathic effect

CPE; lysis and death of cell (not all viruses have CPE)

Difference between lytic cycle and lysogeny for bacteriophage replication in bacteria

lytic- lyse cell
Lysogeny- enter into incorporation w host genome, lie dormant in genome, replication only during binary fission of host

Aka lytic cycle

virulent phage

Aka lysogeny

temperate phage

Animal viral replication stages

adsorption, penetration, uncoating, replication, assembly, release

adsorption

attachment to host cell through receptors
-enveloped- glycoprotein spikes
-naked- surface proteins-looks like a ligand

receptor mediated endocytosis- penetration

whole virus enters cell
- mimics ligand- multiple virus endocytosed at one time
-for naked viruses

translocation (membrane fusion)- penetration

whole virus enters cell
-for enveloped viruses

uncoating

utilizes lysomal function
(may die at this point)

replication (eclipse)

early and late genes
type I: ssRNA -positive polarity
type II: ssRNA -negative polarity
type III: dsRNA
type IV: ssRNA -positive polarity and DNA intermediate

Early and late genes

early: transcribed before replication
late: transcribed at replication

type I

ssRNA w/ positive polarity
transcribe w cluster of proteins

type II

ssRNA w/ negative polarity
-makes a mirror image

type III

dsRNA

type IV

ssRNA w positive polarity and DNA intermediate

release-non-enveloped

lysis

release-enveloped

budding or exocytosis

stationary vs dissemination

migrates to target tissue and stays there vs all over

virus shedding

skin, respiratory tract, gastrointestinal tract, body fluids, vectored(insect/animal bites)

abortive infection

failed infection

lytic infection

cell death

cell alteration due to infection but no cell death

syncytia
inclusion bodies
malignant transformation

syncytia

multinucleated giant cells
-from fusion of viral infected cells
-fusion from changes in cellular membrane, due to inclusion of viral proteins

syncytia is seen typically in which viruses

herpesvirus
paramyxovirus

inclusion bodies

frequently found in infected cells
-are areas containing viral proteins and viral particles
-abnormal aggregations

examples of viral inclusion bodies in animals

intracytoplasmic eosinophilic, intranuclear acidophilic, intranuclear basophilic, and both intranuclear and intracytoplasmic

negri bodies

rabies

guarnieri bodies

small pox

henderson-peterson bodies

molluseum contagiosum

intracytoplasmic eosinophilic

negri, guarnieri, henderson-peterson

intranuclear acidophilic

cowdry type A, cowdry type B, torres

cowdry type A bodies

herpes simplex virus, and varicella zoster

cowdry type B bodies (IA)

polio

torres bodies

yellow fever

intranuclear basophilic

cowdry type B, "owl eyes"

cowdry type B (IB)

adenovirus

"owl eyes"

cytomegalovirus

both intranuclear and intracytoplasmic

warthin finkeldey bodies in Measles

malignant transformation

unrestrained growth, prolonged survival, and morphological changes
-genetic disruption
-increases likelihood that cell will undergo a cancerous mutation

persistent infection

infection without cell death
-true persistant/chronic carrier infections
-latent virus infections

persistent/chronic carrier infections

-continue to produce significant amounts of virus for long periods of time
-i.e. herpes - lock into nerve endings in region- don't flag cytotoxic T cells- cells don't die, neurons

latent virus infections

patients recover from initial infection and virus production stops
-enters cells- no flags- goes dormant and then latter becomes active
i.e. varicella zoster, or when chicken pox resurfaces as shingles

natural barriers

skin,
mucous,
ciliated epithelium,
gastric, bile, etc

nonspecific defenses

fever
interferon
macrophages
natural killer cells

fever

mechanism not completely known
thought to inhibit virus particles and replication

interferon

set of glycoproteins that inhibit growth of viruses by blocking translation of viral proteins
-interferon 2,5-oligonucleotide synthetase, endonuclease, and protein kinase trigger three proteins
-these proteins act to degrade and phosphorylate viral RNA but not cellular RNA

antigen-specific immune response

adaptive immunity
antibodies, T-cells
-hypersensitivity and inflammatory response
-partial immunity
-children's lower severity

hypersensitivity and inflammatory response

symptoms often from immune response to virus not from virus itself directly

partial immunity

may change glycoproteins
-system recognizes half of it- response slower than secondary/memory response but not as slow as primary response

children's lower severity

i.e. chicken pox- less severe reaction than in adult

susceptibility and severity factors

immune status
age
general health
viral dose
genetics of virus-host specific
genetics of host-immunity

antiviral drug therapy

-interferon, antiviral drugs
-there currently is no cure- only management and viral load reduction
-can only give interferon in limited amts before becoming dangerous to the host
-only defeat percentage of virus not all of it

viral cultivation

-needs living system to grow!!!
-bird embryos, cell culture

localized infection

remains confined to a specific tissue

generalized/systemic infection

when organism spreads to other tissue or fluids
-generally only one organism

focal infection

when a localized infection breaks loose and spreads to another tissue

toxemia

infection remains localized but a toxin is produced and travels to different tissue group

mixed infection
(synergistic mixed infection)

several agents establish themselves simultaneously at the infection site

primary infection

first infection

secondary infection

when primary infection is complicated by a second microbe

acute infection

infections that come on rapidly with severe but short lived effects

chronic infection

progress or persist over long periods of time

sign

OBJECTIVE evidence of disease noted by an observer

symptom

SUBJECTIVE evidence of disease as sensed by a patient

early warning symptoms and signs

fever, inflammation, leukocytosis, leukopenia, antibody titer

leukocytosis

abnormal increase of white blood cells

leukopenia

lowering of white blood cells

asymptomatic

infected but showing no signs of the infection

portals of exit

-respiratory, salivary, mucous, sputum, nasal discharge,
-skin scales,
-fecal,
-urogenital,
-blood

prevalence

total number of existing cases with respect to the
entire population

incidence

number of new cases over a certain time period

mortality

number of deaths

morbidity

number afflicted with infectious disease (symptomatic and asymptomatic)

endemic

infectious disease that exhibits steady frequency over a long period in a particular geographic locale

sporadic

occasional cases are reported at irregular intervals in unpredictable locales

epidemic

prevalence of an endemic or sporadic disease- increasing beyond what is expected for that population

pandemic

epidemic that spreads across continents

living reservoirs

(people)
asymptomatic, incubation, covalescent, chronic, passive carriers

asymptomatic carrier

hard to find and treat

incubation carrier

will eventually develop signs and symptoms

convalescent carrier

has recovered from signs and symptoms but still capable of transmitting infection to others

chronic carrier

an individual who acts as host to pathogenic organisms for an extended period without displaying any signs of disease

passive carrier

persons who mechanically transfer a pathogen without ever being infected by it

animal reservoirs

vectors
-biological and mechanical

vector

animal that transmits microbe from one host to another

biological vector

participates in life cycle

mechanical vector

no participation in life cycle

zoonosis

indigenous to animals but transmissible to humans

non-living reservoir

fomite-
-an inanimate object i.e. pens clothes

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