Viruses and fungi Flashcards
Gram - Cell Envelope
outer membrane
cell wall
periplasmic space
cell membrane
cell membrane
and functions
phospholipid layer
active transport and energy production.
cell wall
peptidoglycan crosslinked meshwork
peptidoglycan layer made up of
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)
Amino Acids
= building blocks added to growing polypeptide chain
cell wall functions
osmotic barrier
antibiotic site of action
provides shape: rod, coccus, spiral
outer membrane
lipopolysaccharide (Endotoxin)
functions of outer membrane
permeability barrier (porin proteins) sometimes bacteria will change these proteins(PBP)
Virus
Obligate intracellular parasite
Cannot make energy, completely dependent on host cell
virus structure
Noncellular
no organelles
no ribosomes
Virus structure (made up of)
genome (made of DNA or RNA)
capsid (protein shell)
envelope - only some have this.
envelopes have
spikes containing glycoprotein/lipid
Virus capsid
Protein shell that provides shape
assembly of identical protein subunits
ex. icosahedral
Virus replication cycle
attachment enter and uncoating replication assembly release
attachment
susceptible cell: receptors (glycoprotein) for the cirus on the cell surface
Specific distribution to specific tissues
spikes (attachment)
recognize CD4 receptors on the host cell
ex. on WBC for HIV
Viral entry (3)
- Endocytosis
- Direct fusion
- Nucleic acid translocation
endocytosis
Majority of nonenveloped viruses
entire virus engulfed by teh cell and enclosed in a vacuole
direct fusion
Enveloped viruses
Envelope fuses with the cell membrane of host cell with spikes trapped in membrane
protein capsi transferred into the cell (protein and nucleic acids inside cell)
nucleic acid translocation
Rare nonenveloped viruses
Capsid adheres to host cell membrane -> partial rearrangement of virion -> nucleic acid (only) passes directly into host cell
dsDNA Replication
Virus uses host RNA Polymerase to make RNA: capsid proteins and DNA polymerase
Virus uses the created DNA polymerase to replicate DNA
RNA Replication (2)
some can act directly on the ribosome
retroviruses
(+) RNA Virus (Retroviruses)
not used directly as mRNA
Uses own virion reverse transcriptase to make dsDNA -> integrated into the host cell’s chromosome
integrated dsDNA transcribed with normal cell machinery ->mRNA)
reverse transcriptase enz process
creates ssDNA complementary to the retroviral RNA
- > ssDNA -> complementary DNA
- > dsDNA enters host cell nucleus
- > Latent infection
latent viral infections
the persistence of viral genomes
latent viral infection ex’s
herpes simplex and varicella - latent infection in sensory neurons
HIV-1latent infection of resting memory CD4 (+) T cells.
nonenveloped viruses assembly and release
lysis - kill
enveloped viruses assembly and release
Bud through the host cell plasma membrane - slower killing of the host once enough of the embrane is gone.
Diagnostic detection of viruses (5)
direct detection with microscopy Viral culture Serology Amplification of the nucleic acid Antigen detection
direct detection with microscopy of viruses
for viruses that are very difficult to grow
rarely done, time consuming - look at the shape
electron microschope used - impractical
Viral culture
Many different tissue types are inoculated
if there is a virus - monolayer of cells will be destroyed
be aware of cytopathic effect (CPE)
Cytopathic effect
nonspecific viral culture
Effect the virus infection has on the appearance of cell in culture viewed by light microschope after pt specimen is inoculated onto the cell culture and the virus has replicated
can’t tell which virus it is, just that there is a virus
Serology
detection of the immune response by the host against the infecting agent
Detecting specific immunoglobulin (antibody)- need to know what you are looking for
very common way of detecting viruses
ex. Hep B
PCR
specfici segment of RNA or DNA
genetic material extracted from pt sample.
genetic matieral is multiplied many times and then detected
extremely sensitive and specific
becoming the standard
antigen detection:
derect ttest on a patient specimen
detect specific antigen of the particular organism you are looking for.
example of antigen detection
in kids with rotavirus
stool contains the antibody binded to the antigen - can detect it
Antiviral agents
Viral uncoating (penetration): stop virus from being uncoated = neutral virus
nucleic acid synthesis: reverse transcriptase inhibitors (HIV)
Assembly and Release: Protease inhibitors (HIV) - Flu.
Eukaryotic cell structure
Cytoplasmic membrane
Cell wall
Fungal cytoplasmic membrane made of
ergosterol (primary sterol)
Cell wall made of
Chitin (No peptidoglycan)
reproduction of funi
Spores or Canidia
charachteristics of the spore that is used to classify the fungi
size
shape
arrangement`
growing yeast on and in this much time
bacteriology or mycology media
24-48 hours.
Yeast in comparison with bacteria
budding cells
larger
gram stain on yeast
will work but call them purple cells
mold growth
through the development of hyphae: multicellular fungal elements
hyphae grow to
mycelium
enough hyphae to be visible
ex. green stuff in the cheese
meningitis
yeast infection (cryptococcus neoformans) - affects the lining of the brain yest with large capsule (pathogenicity factor)
2 types of hyphae
reproductive hyphae - not seen in the host
branches
vegetative hyphae - seen in the host
roots
Growing of molds
most from environment
specific media with antibiotics to inhibit bacteria and support fungi
optimize environmental conditions lower temp 30 degrees
Takes weeks.
ORDER FUNGUS CULTURE SPECIFICALLY
Dimorphic Fungi
grow depending on temperature
yeast at 37
mold at 30
histoplasma capsulatum
follow bird migration and great lakes - damp soils
resp infection
blastomyces dermatitidis
Follow bird migration and great lakes
cause blastomycosis
coccidioides immitis
North America
Causes coccidioidomycosis (valley fever)
creates lung tumor - need lung biopsy.
all the Fungi infections start with
respiratory infections by breathing them in.
Target sites for antifungal therapy
cell wall: inhibit chitin
cell membrane - inhibit ergesterol
mitosis
cell membrane tartgeted antifungals
Polyenes - Ergosterol incorporation
- very costly, IV, for serious diseases
azoles: Ergosterol synthesis: - more common, treat serious, oral and IV
How do you get fungal disease (2)
Change in host
environmental exposure
change in hist (2)
antibiotics:
- also kills off some normal flora therefore, susceptible to fungal infection
immunosupression
a. neutropenia - susceptible to aspergillus
b. T cell destruction (AIDS) - susceptible to histoplasma
Environmental superficial infections
dermatophytes
Ringworm
ringworm can only infect
skin
hair
nails
because of keratin as growth substrate
disease state of dermatophytes is called
TInea
to get dermatophitic infection you need
prolonged direct contact - hyphae can get to the next person and survive.
Molds names to recognize
Epidermophyton
Trichophyton
Microsporum
yeast name
Candida
Factors affecting systemic infection (systemic mycoses)
route of exposure (aerosol)
previous exposure/immunity
status of immune system
amount of inoculum
detection of fungi
culture (Y-1-3 day, dermatophytes (1-3wks, systemics (3-6wks) Direct smears KOH Mount Calcoluor Gram Stain Silver Stain.
