Microbiology in Ophthalmology Flashcards
What causes bacterial conjunctivitis in under 2’s?
Staph Aureus
Neisseria gonorrhoea
Chlamydia thrachomatis
What causes bacterial conjunctivitis in adults?
Staph aureus
Strep pneumonia
Haemophilus influenze
Describe the treatment of bacterial conjunctivitis
Swab- so you know what to do if it doesn’t respond to antibiotics
Topical antibiotics; chloramphenicol
- ointment=thick and unpleasant
- drops=kept in fridge
What should you be wary about regarding chloramphenicol?
Avoid if aplastic anaemia
Allergy- if patient describes worsening symptoms
Describe adenovirus conjunctivitis
Fairly common- ‘pink eye’
Most of the time- red watery eye
Self-limiting
Contagious
Describe herpes simplex conjunctivitis
Found in patients if they have vesicles around the eye
Describe herpes zoster conjunctivitis
Virus goes to nerve ganglion to dwell in it; trigeminal=infection
Unpleasant, needs treated quickly
Cellulitis changes, some conjunctivitis, fewer keratitis
What is keratitis?
Further back in the eye and less common than conjunctivitis
Describe the history of chlamydial conjunctivitis?
Often chronic history
Unresponsive to treatments
When should you suspect chlamydial conjunctivitis?
Bilateral conjunctivitis in young adults
What are the other features of chlamydial conjunctivitis?
urethritis, vaginitis
What features of the eyes suggest chlamydial conjunctivitis?
Follicular change, this can cause scarring
What is a hypopyon?
white cells in the cornea causing white deposit
How is bacterial keratitis with hypopyon treated?
Admission for hourly drops and daily review
How serious is bacterial keratitis with hypopyon?
Serious, sight threatening
What is bacterial keratitis with hypopyon associated with?
Co-morbid condition; rheumatoid, contact lenses
Which viruses cause keratitis?
Herpes
Adenovirus
Describe the symptoms in herpetic keratitis
Pain
Can’t open eye, no history of trauma
Reduced corneal sensation
How should herpetic keratitis be treated?
Anaesthetic drops and antiviral
How should herpetic keratitis NOT be treated?
Steroids- cause a corneal melt and perforation
Describe the symptoms in keratitis caused by adenovirus
Poor vision
Conjunctivitis too
Contagious
follows a URTI
How is keratitis caused by adenovirus treated?
With topical antibiotics to prevent secondary infection - topical stewards if chronic
What does a dendritic ulcer look like and when is it seen?
Branching tree
Herpetic viral keratitis
When is fungal keratitis seen?
Very rare
Contact lenses
What is acanthamoeba?
Lives in contact lenses that have been washed in tap water
Painful and difficult to resolve
What should you do if you suspect a contact lens is the cause of infection?
Send for culture
What other fungi cause fungal keratitis?
Pseudomonas aeruginosa
What is fungal keratitis with hypopyon?
Trauma associated with a piece of vegetation
Grumbles on and patient pays little attention
How does the onset of fungal and microbial keratitis vary?
Fungal keratitis is much more indolent
Usually a trauma from vegetation in fungal
What can be seen in orbital cellulitis?
Proptosis- caused by pus in orbit
What is orbital cellulitis associated with?
Paranasal sinusitis; sinus infection goes through the bone of the orbit and spreads
How will a patient with orbital cellulitis present?
Pain on eye movement
Pyrexial
Extension from focal orbital infection to mebomian/lacrimal gland
Post-op
How should orbital cellulitis be investigated?
CT scan to identify orbital abscess
How to differentiate between preseptal and orbital cellulitis?
- pre-septal just in the outer surface of the skin, there is not an affect on the function of the eye
- bear in mind the child will be sore and not move the eye; this doesn’t mean they can’t
Which organisms cause orbital cellulitis?
Staphylococci Streptococci Coliform Haemophilus influenzae Anaerobes
How should orbital cellulitis be managed?
If suggestion of restriction of muscles or optic nerve (loss of colour, follow a finger) then broad spectrum AB and monitor
Drainage of abscess
What is endopthalmitis
Devastating infection inside the eye
Post-surgical or endogenous
How will a patient with endopthalmitis present?
Painful +++
Decreasing vision
Very red eye
What is the risk with endopthalmitis
Can extend into cranial cavity
Which organisms are responsible for endopthalmitis?
Conjunctival organisms
Staph epidermidis
How is endopthalmitis treated?
Intravitreal amikacin/ceftazidime/vancomycin and topical antibiotics
Potential systemic antibiotics
What is chorioretinitis?
Inflammation of the choroid and retina
What can cause chorioretinitis?
CMV in AIDS
Toxoplasma gondii
Toxocara canis (worm)
What will be observes in chorioretinitis in patients with CMV in AIDS?
Low CD4+ Count
Huge areas of exudation and haemorrhage; these patients will go blind
What will be observes in chorioretinitis in patients with toxoplasma gondii?
Mild flu-like illness
Where is toxoplasma gondii acquired?
Cats and raw meat
How is toxoplasma gondii acquired?
In immunocompromised patients it enters latent phase and causes cyst formation
How is toxoplasma gondii treated?
Can be macular- no treatment
Systemic treatment if sight threatening
What is toxocara canis?
Parasitic nematode
Affecting cats/dogs
Why is toxocara canis self-limiting?
Cannot replicate in humans, remains immature larvae
What does toxocara canis cause?
Formation of granulomas which can cause irreversible visual loss
How should eye infections be diagnosed?
Swab for culture
-bacterial, chlamydial, viral (USE ANAESTHETIC)
Corneal scape in bacterial keratitis
Aqueous/vitreous culture in endopthalmitis
Microscopy/culture for acanthomoeba
Serology for toxoplasma and toxocara
How does chloramphenicol work?
Inhibits peptidyl transferase enzyme (stops bacterial protein being made)
What is chloramphenicol bactericidal against?
Strep and haemophilus
What is grey baby syndrome?
Baby overdose of chloramphenicol
Which antibiotics inhibit cell wall synthesis?
Penicillins and cephalosporins due to B lactam ring
What are penicillin and cephalosporins active against?
Staph
Which antibiotics inhibit nucleic acid synthesis?
Quinolones e.g. oflaxacin (inhibit DNA gyrase)
What is a common contaminant in eye drop bottles?
Pseudomonas
How does aciclovir work?
Inhibits viral DNA synthesis
When are antivirals used?
Dendritic ulcers of the cornea
How is chlamydial conjunctivitis treated?
Topical oxytetracycline
May also need azithromycin if other manifestations
How should bacterial keratitis be treated?
A 4-quinolone
-ofloxacin
Treats most gram -ve including coliform, pseudomonas and influence but NOT step pneumoniae
Gentamicin and cefuroxime
-treats gram +ve and gram -ve
