Microbiology + Immunology Flashcards
what infections can happen in the eye
Conjunctivitis
Cornea= keratitis
Entire globe= endophthalmitis
Cellulitis (skin around the eyes)
bacteria that causes neonates bacterial conjunctivitis
Staph aureus
Neisseria gonorrhoeae
Chlamydia trachomatis
what must happen in cases of neonate bacterial conjunctivitis
all cases must be referred to ophthalmology
bacteria that causes other ages bacterial conjunctivitis
Staph aureus
Strep pneumoniae
Haemophilus influenzae (especially in children)
Tx for bacterial conjunctivitis
Swab
Topical Chloramephenical
when should Chloramephenical not be used
history of aplastic anaemia or allergy
what are signs that the patient is allergic to Chloramephenical
worsening symptoms
skin becomes red and itchy
what are causes of viral conjunctivitis
Adenovirus
Herpes simplex
Herpes zoster
what is suggestive of chlamydial conjunctivitis
Often chronic history
Unresponsive to treatments
Suspect in bilateral conjunctivitis in young adults
May or may not have symptoms of urethritis, vaginitis
what is seen in chlamydial conjunctivitis
follicles under upper eye lid intense erythema subtarsal scarring (caused by follicles bursting)
what is seen in bacterial keratitis
hypopyon - leukocytic exudate, seen in the anterior chamber
appears as white mark in red eye
Mx of bacterial keratitis
Scrap hypopyon
Admission + Hourly drops
Associated w/ contact lens wearers
what viruses can cause keratitis
Herpes
Adenovirus
what is an indication of a herpetic keratitis
dendritic ulcer
Sx of herpetic keratitis
Very painful
Can be recurrent
recurrences eventually result in reduced corneal sensation
what is NOT given in the treatment of herpetic keratitis and why
Steroids
Can cause Corneal melt
what is seen in adenoviral keratitis
subepithelial infiltrates
features of adenoviral keratitis
Bilateral
Usually follows an URTI
Contagious
May affect vision
Mx of adenoviral keratitis
Can give topical AB to prevent secondary infection
Can give steroids to speed up recovery if becomes chronic
what are fungal causes of keratitis
Acanthamoeba
Pseudomonas aeruginosa
what can lead to fungal keratitis
contact lenses
trauma Hx of trauma from vegetation
features of orbital cellulitis
Painful – especially on eye movements Proptosis Often associated with paranasal sinusitis Pyrexial Sight threatening
IX for orbital cellulitis
CT scan
what causes orbital cellulitis
spread via paranasal sinus infection
what organisms are seen in orbital cellulitis
Staphylococci Streptococci Coliforms Haemophilus influenzae anaerobes
Tx of orbital cellulitis
Broad spectrum AB
Surgery
what is Endophthalmitis
infection is in the whole eye
what causes Endophthalmitis
post-surgical infection
trauma
endogenous (low grade sepsis/endocarditis)
Sx of Endophthalmitis
Painful +++, with decreasing vision
Very red eye
Sight threatening - lose vision very quickly
what organisms cause endophthalmitis
Staph epidermidis most commonly
Tx for endophthalmitis
Intravitreal amikacin and vancomycin and topical antibiotics
what is choridoretinitis
inflammation of the choroid of the uvea
what can cause choridoretinitis
CMV in AIDS
Toxoplasma gondii
Toxocara canis (worm)
what is toxoplasmosis
Protozoan infection - toxoplasmosis gondii
Mild flu like illness
Get from cats and dogs
what happens in immunocompetent patients with toxoplasmosis
it enters latent phase with cysts forming
Can reactivate
Requires systemic treatment if sight threatening
what is toxocara
Parasitic nemotode (roundworm)
Affects cats or dogs
Unable to replicate in humans
Remains an immature form of the worm (larvae)
features of toxocara
self limiting as they cannot replicate
However, can form granulomas which can cause irreversible visual loss
when is ‘Swabs for Culture’ used to diagnose an eye infection
bacterial, chlamydial, viral
Corneal scrapes in bacterial keratitis
what Ix is done in cases of endophthalmitis
Aqueous/vitreous for culture
what is done in cases of acanthamoeba
Microscopy/culture
what is done in cases of toxoplasma and toxocara
Serology
what are Chloramphenicol side effects
Allergy
Irreversible aplastic anaemia
Grey baby syndrome
what is dacryocystitis
infection of the lacrimal sac, secondary to obstruction of the nasolacrimal duct at the junction of lacrimal sac
Tx for viral conditions
Aciclovir - used for dendritic ulcers of the cornea
Tx for Bacterial conjunctivitis
chloramphenicol - (treats most bacteria except Pseudomonas aeruginosa)
fusidic acid - (treats Staph. aureus)
gentamicin- (treats most Gram negative bacteria including Pseudomonas aeruginosa)
Tx for chlamydial conjunctivitis
topical oxytetracycline
Tx for bacterial keratitis
A 4-quinolone (Ofloxacin)
OR
Gentamicin and cefuroxime
what is part of the immediate, innate immune response
Complement proteins
Mast cells
Macrophages
features of innate immune system
Rapid, general response (mins-hours)
Targets groups of pathogens
- Responds to only a limited number of microbial structures
No memory
features of adaptive immune system
Gradual response (>days)
Targets specific pathogens
- Can responds to a huge array of different microbial structures
Memory
what chemicals are contained in tears for immune protection
Lysozyme - works against gram –ve, fungi
Lactoferrin and transferrin - works against gram +ve
Complement
Tear lipids - antibacterial to cell membranes
Secretory IgA- prevents attachment
what cells are contained in tears for immune protection and what are there function
Neutrophils
- attracted by chemotaxis
- Scavengers-release free radicals, enzymes
Macrophages
- Phagocytosis of damaged cells
- Help to trigger adaptive immune system
Conjunctival mast cells
- Vasoactive mediators
what is immune privilege
parts of the body that able to tolerate the introduction of antigens without eliciting an inflammatory immune response
why does the eye need immune privilege
eye is very small
immune response can cause damage
what is the only part of the eye with lymphatic drainage
conjunctiva
what cells act as APC in the conjunctiva
dendritic cells
features of cornea and sclera
Avascularity
No lymphphatics/lymphoid tissue
Downregulated immune environment
Relative lack of antigen presenting cells
what is the role of cornea and sclera
tough collagen coat
role of vitreous, choroid and retina in immune system
Blood-ocular barrier
Relative lack of APCs
Downregulated immune environment
what are the hypersensitivity classifications
Type I: Immediate hypersensitivity
Type II: Direct cell killing
Type III: Immune complex mediated
Type IV: Delayed type hypersensitivity
what happens in type I hypersensitivity reaction
- mast cells Express receptors for Fc region of IgE antibody on their surface
- On encounter with allergen, B cells produce antigen-specific IgE antibody
- allergen is cleared
- Residual IgE antibodies bind to circulating mast cells via Fc receptors.
- re-encounter with allergen
- Allergen binds to IgE - coated mast cells & disrupts cell membrane
- Release of vasoactive mediators – histamine, tryptase, also increased cytokines and leukotriene transcription
what happens in Type II hypersensitivity
Cells killed either by:
Macrophages/natural killer cells
Complement (membrane attack complex)
what is an example of type II hypersensitivity in the eye
Ocular cicatricial pemphigoid
what is an example of type III hypersensitivity in the eye
Autoimmune corneal melting
what happens in type IV hypersensitivity
T helper cells activated by intracellular pathogens
Clonal expansion
When re-exposed, macrophages attracted
example of type IV hypersensitivity in the eye
corneal graft rejection
