Ocular Microbiology and Viruses Flashcards
(24 cards)
key characteristics of a virus?
Viruses are non-living entities made up of genetic material (DNA or RNA) encased in a protein coat called a capsid.
Some viruses have an additional lipid envelope derived from the host cell membrane.
What are the two types of viral genomes?
DNA viruses: Viruses with double-stranded (dsDNA) or single-stranded (ssDNA) DNA.
RNA viruses: Viruses with single-stranded (ssRNA) or double-stranded (dsRNA) RNA.
How do enveloped viruses differ from non-enveloped (naked) viruses?
Enveloped viruses have a lipid membrane surrounding their protein coat and are more sensitive to environmental conditions.
Non-enveloped (naked) viruses lack an envelope and are more resistant to environmental stress (heat, drying).
the main steps involved in the replication cycle of viruses?
Attachment: Virus binds to specific receptors on the host cell.
Entry: Virus or its genome enters the host cell.
Replication and Transcription: Viral genome is replicated and transcribed within the host cell.
Assembly: New viral particles are assembled from synthesized components.
Release: New virions are released from the host cell, often causing cell lysis.
What is adenovirus, and what ocular conditions does it cause?
Adenovirus is a non-enveloped DNA virus.
It is a major cause of epidemic keratoconjunctivitis (EKC), which causes conjunctival redness, watery discharge, swelling, and corneal involvement.
Spread through direct contact or aerosolized droplets.
How does adenovirus cause epidemic keratoconjunctivitis (EKC)?
Adenovirus infects the conjunctiva and cornea, leading to acute conjunctivitis and keratitis.
Symptoms include pain, photophobia, and a foreign body sensation.
Can lead to long-term corneal scarring in severe cases.
What is the structure of Herpes Simplex Virus (HSV)?
Herpes Simplex Virus is a double-stranded DNA virus with an icosahedral capsid and an envelope derived from the host cell membrane.
What ocular infections can Herpes Simplex Virus (HSV) cause?
Herpes Simplex Keratitis: Most common cause of corneal blindness worldwide, presenting with dendritic lesions on the cornea.
Herpes Simplex Conjunctivitis: Causes red eye, pain, and tearing.
What is Herpes Zoster Ophthalmicus (HZO), and what ocular symptoms does it cause?
Herpes Zoster Ophthalmicus is caused by the reactivation of the Varicella-Zoster Virus (VZV), typically along the ophthalmic branch of the trigeminal nerve.
Symptoms include pain, vesicular rashes, conjunctivitis, keratitis, and potentially blindness due to corneal involvement or uveitis.
What is the difference between HSV-1 and HSV-2 in terms of ocular infections?
HSV-1: Commonly causes ocular infections such as keratitis and conjunctivitis.
HSV-2: Typically causes genital herpes but can cause ocular infections through vertical transmission or autoinoculation.
How is Varicella-Zoster Virus (VZV) related to chickenpox and shingles?
VZV causes chickenpox during primary infection and lies dormant in dorsal root ganglia.
Reactivation leads to shingles, which can result in Herpes Zoster Ophthalmicus (HZO), causing ocular complications such as keratitis, uveitis, and chorioretinitis.
What ocular manifestations are associated with HIV infection?
HIV-related retinopathy: Common in HIV patients, with symptoms like cotton-wool spots, microaneurysms, and retinal hemorrhages.
Cytomegalovirus (CMV) retinitis: Can cause retinal detachment and vision loss if untreated.
How does HIV lead to ocular complications?
HIV weakens the immune system, making the eyes more susceptible to infections like CMV retinitis and Kaposi’s sarcoma.
HIV retinopathy is commonly seen in immunocompromised individuals with poorly controlled HIV.
What is the role of COVID-19 (SARS-CoV-2) in ocular infections?
SARS-CoV-2 has been associated with conjunctivitis, presenting with redness, watery discharge, and foreign body sensation.
The virus can be shed in tears, leading to possible ocular transmission.
What are the common ocular manifestations of Coronavirus (SARS-CoV-2)?
Conjunctivitis: Common symptom in the early stages of COVID-19.
Tearing, redness, and chemotic conjunctiva (swelling) are typical.
What is the significance of viral DNA in ocular infections?
The viral DNA of herpesviruses and adenoviruses can integrate into the host genome, causing latent infections that may reactivate under stress or immunocompromise, leading to recurrent ocular outbreaks.
How can ocular microbiology assist in diagnosing eye infections?
Microbial cultures and PCR tests help identify the specific viral or bacterial pathogen causing ocular infections, guiding effective treatment strategies and determining the need for antiviral or antibiotic therapies.
What role does the immune system play in ocular infections caused by viruses?
The immune response to viral infections can lead to inflammation in the eye, such as uveitis or keratitis, and may contribute to long-term ocular complications if not controlled.
What is the treatment approach for Herpes Simplex Keratitis?
Antiviral medications, such as acyclovir or valacyclovir, are the primary treatment for HSV keratitis to reduce the risk of corneal scarring and vision loss.
What is the importance of vaccination for herpes zoster in ocular health?
Herpes zoster vaccination reduces the risk of shingles and Herpes Zoster Ophthalmicus (HZO), preventing severe ocular complications like keratitis and uveitis.
the structure of an ‘enveloped’
virus?
A nucleic acid, a protein and a glycoprotein shell
chaacteristics of a ‘non-enveloped’’ virus?
Resistant to drying
Not affected by heat
Can survive in acidic conditions
Not affected by detergents
Spreads easily via surfaces and objects
which virus causes shingles
Varicella Zoster Virus
risk factor for reactivation of
‘Herpes Zoster Ophthalmicus’?
Fever
Emotional stress
Local trauma
Immunosuppression
