Eye Infections

Question 1

Staphylococcus aureus

Answer 1

Eye Infx
• Gr+ cocci, often *clusters
• Ubiquitous
• Normal microbiota—anterior nares, skin, mucous membranes (sometimes throat, perineum, vagina)
• Non-motile, non-endospore forming
• Polysaccharide capsule
• Facultative anaerobe 
• Catalase + 
• *Coagulase +
• Forms pus 
• Novobiocin Sensitive 
Dx
One of leading causes of *conjunctivitis, blepharitis, dacryocystitis, orbital cellulitis
LABS
• *Mannitol Fermentation
• *True Hemolysis (ß-Hemolysis) 
VF
• *Protein A
• *Cytolytic Exotoxins 
• *Enzymes 
• *Fibronectin-Binding Protein
• Capsule

Question 2

Staphylococcus epidermidis

Answer 2

Eye Infx
• Gr+ cocci, often *clusters
• Ubiquitous
• Normal microbiota—skin, mucous membranes (major healthcare-associated opportunities, major cause prosthetic/catheter infection)
• Non-motile, non-endospore forming
• *Loose slime layer (monosaccharides, protein)
• Facultative anaerobe
• Catalase +
• *Coagulase -
• *Mannitol Fermentation (-) 
• Novobiocin Sensitive  
LAB
• *Gamma-hemolysis 
VF
• *Adhesions
o **Slime layer
o **Biofilms

Question 3

Adenovirus

Answer 3

Eye Infx
• *Linear, dsDNA
• Replicates in nucleus
• *Icosahedral capsid
• *Naked (non-enveloped)
• Primarily attacks *mucoepithelial cells conjunctiva, respiratory tract, GI tract, GU tract
DX
• Ocular infections/adenovirus conjunctivitis:
1) Follicular conjunctivitis→ may progress to keratoconjunctivitis
2) Keratoconjunctivitis → corneal opacity that may last for yrs
VF
• *Fiber protein adhesion
• Lytic cycle (sx occur)
• *Latent cycle in lymphoid tissues

Question 4

Herpesviridae

Answer 4

Eye Infx
• Linear, dsDNA genome 
• Replicates in the nucleus 
• Icosahedral
• Enveloped, spherical to pleomorphic
• Large (150-200 nm)
• Includes HSV-1, HSV-2, Varicella-zoster virus, Epstein-Barr virus, Human cytomegalovirus, Human Herpesvirus 6, HHV-7 & HHV-8
- **latent in sacral ganglia
LAB
- *Tzanck test

Question 5

Onchocerca volvulus

Answer 5

Eye Infx
• Nematode, filarial worm
• Females produce 1000’s microfilariae/day → wander tissues, lymphatics, eyes (vs. loa loa = adults wandering)
• Causes *Onchocerciasis = River blindness
• #2 infectious cause blindness in the world
SX
- *lesion on cornea, optic nerve inflammation–>blindness
• Asymptomatic to *itchy rashes, nodules, vision changes
• Skin inflamm., itching can result in long-term damage to skin
o Color changes = *leopard skin
o Thinning, loss of elastic tissue = *cigarette paper appearance
o Loss of elastic tissue + swollen lymphatics = *hanging groin
TX
- *ivermectin (kills microfilariae not adults) + nodulectomy