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15 Cards in this Set
- Front
- Back
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Virus Structure |
Smallest infectious organisms (20-300nm)
Obligate intracellular parasites
Lack cell wall and metabolic machinery
Dependent on host for replication
Access to host usually receptor-mediated |
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Steps in Viral Replication |
1. Attachment of virus to host cell using specialized receptors on the virus and host cell
2. Penetration of virus into host cell and uncoating of virus
3. Duplication of viral DNA or RNA using host DNA/RNA
4. Assembly of viral genome and capsid within host cell and then release of progeny
5. The host cell can then either die or survive, depending on the virus and host cell type |
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DNA Viruses (4) |
Poxviruses (smallpox)
Herpesviruses (chickenpox, shingles, cold sores, glandular fever)
Adenoviruses (sore throat, conjunctivitits)
Papillomaviruses (warts) |
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DNA Viruses Replication |
*Viral DNA enters hose cell nucleus *Transcription into mRNA occurs catalyzed by host cell RNA polymerase *Translation of mRNA into virus-specific proteins *There proteins are enzymes that synthesize more viral DNA or make up the viral coat and envelope *Complete visions are released by budding or after host cell lysis |
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RNA VIruses (8) |
Orthomyxoviruses (influenza)
Paramyxoviruses (measles, mumps, resp. infections)
Rubella virus (German measles)
Rhabdoviruses (rabies)
Picornaviruses (colds, meningitis, poliomyelitis)
Retroviruses (AIDS, T-cell leukemia)
Arenaviruses (meningitis, Lassa fever)
Hepadnaviruses (serum hepatitis)
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RNA VIruses Replication |
*Enzymes within vision synthesize its mRNA from viral RNA template or viral RNA serves as its own mRNA *Translated by host cell into various enzymes, including RNA polymerase and into structural proteins of the virion *Host cell nucleus is usually not involved in viral replication |
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Herpesvirus [size, structure, sensitivity, spread and identifications to eye infections] |
Size 120-300nm, have DNA genomes and outer lipid membrane (envelope)
Sensitive to drying and adverse conditions
Spread by inoculation of susceptible mucous membranes of direct cell-to-cell contact
Over 100 identified but only 5 cause human eye infections with any frequency *HSV-1, HSV-2, VZV, CMV, Epstein-Barr virus |
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Herpesvirus: HSV-1 [what does it cause, type of latency, how the host immune system is involved and triggers] |
Causes sores around lips and mouth
Most frequent cause of primary and secondary recurrent eye infections -> Blepharitis, Conjunctivitis, epithelial keratitis, uveitis, retinitis, acute retinal necrosis (ARN)
Neuronal or ganglionic latency
Host immune system influences the rates of activation. Immunocompromised patients tend to have more frequent reactivations and more severe disease manifestations
May be triggered by illness, physical or emotional stress, fatigue or trauma |
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Adenovirus [size, structure, what it causes, tx] |
Size 70-100 nm
DNA genetic material, no lipid envelopes and can survive on inanimate objects
Certain serotypes can cause conjunctivitis and Epidemic keratoconujunctivitis (EKC) |
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Betadine [uses, % concentration, C/i] |
Off-label use to tx EKC; used widely in ophthalmology to prepare eyelids, eyelashes and conjunctiva before intraocular surgery b/c of its wide spectrum of micro-biocidal activity
5% povidone-iodine ophthalmic solution
Not well understood but povidone-iodine effective in treating adenovirus
C/I in patients with iodine allergy |
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Betadine Tx |
*Drape patient *Instill 3 drops of anesthetic to the affected eye *Instill a drop of NSAID *Instill 5 drops of Betadine 5% *Spread Betadine over eyelid margin and eyelashes *Instruct patient to move eye left, right, up and down *Wait 60 seconds *Irrigate thoroughly to remove Betadine *Instill another drop of NSAID or anesthetic for discomfort |
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CMV retinitis - what is it |
Most common opportunistic eye infection in patients with AIDS and immunocompromised transplant patients |
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How is CMV treated? |
Antiviral are administered in 2 stages: induction therapy for disease regression followed by maintenance therapy
Treated with antivirals: *Cidofovir (Vistide) -IV *Foscarnet sodium (Foscavir) - IV *Ganciclovir sodium (Cytovene) - IV, Oral *Ganciclovir sodium (Vitrasert) - Intravitreal insert Valganciclovir (Valcyte) - Oral 1. |
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Vitrasert design |
Contains a minimum of 4.5 mg ganciclovir
Contains a ganciclovir tablet which contains the inactive ingredient, magnesium sterate (0.25%).
Each tablet is coated with polyvinyl alcohol and ethylene vinyl acetate polymers
Designed to release the drug over 5-8 months |
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Vitrasert Implantation |
Inserted surgically into the posterior segment of eye through a 5.5mm pars plans incision
Implantation normally takes less than one hour, requires only local anesthesia and is conducted in an outpatient, day-surgery setting |
