Microbiology Flashcards
What is the name given to an infection of the entire eye?
Endophthalmitis
Keratitis is an infection of what part of the eye?
Cornea
What is cellulitis with regards to the eye?
An infection of the skin around the eye
How does bacterial conjunctivitis usually present?
- red eye
- pus discharge
When should you worry about bacterial conjunctivitis?
If it is present in neonates
these should all be referred to ophthalmology
What organisms usually cause bacterial conjunctivitis in neonates?
Staph aureus
Neisseria gonorrhoeae
Chlamydia trachomatis
What organisms cause bacterial conjunctivitis in other ages?
Staph aureus
Strep pneumoniae
Haemophilus influenzae (especially in children)
How is bacterial conjunctivitis treated?
Swab
Topical antibiotic - chloramphenicol (drops vs ointment)
When should chloramphenicol not be given?
if history of aplastic anaemia
OR should be stopped if suspicion of allergy
Where should chloramphenicol eye drops be kept?
Fridge
Why do patients struggle to use chloramphenicol gel?
It is very thick and difficult to apply to the infected eye
What viruses commonly cause conjunctivitis?
Adenovirus
Herpes simplex
Herpes zoster
How does adenovirus conjunctivitis present?
Red bloodshot eye
no pus
What can be a sign of herpes simplex conjunctivitis?
vesicles beside the eye
What presentation can make you suspect chlamydial conjunctivitis?
Chronic problem (many infections)
Unresponsive to treatments
Present in young adults
May or may not have symptoms of urethritis, vaginitis
What sign of chlamydial conjunctivitis can be found in the eyelid?
Follicular change (looks like rice)
What complication can chlamydial conjunctivitis cause?
subtarsal scarring
How does a bacterial keratitis usually appear?
white clouded areas on cornea
hypopyon (white layer of fluid) at bottom of cornea
How is bacterial keratitis treated?
- admission for hourly drops (Ofloxacin)
- Daily review
Bacterial keratitis usually occurs when there is other corneal pathology present. TRUE/FALSE?
TRUE
Usually in association with other corneal pathology or contact lens wear
What viruses most commonly cause keratitis?
Adenovirus
Herpes
What sign is distinctive of herpetic keratitis?
Dendritic ulcer
What treatment should not be used in herpetic keratitis?
Corneal melt and perforation of the cornea
Ulcer dissolves
Adenovirus keratitis is usually bilateral and contagious. TRUE/FALSE?
TRUE
What type of infection usually precedes an adenovirus keratitis?
Upper Respiratory Tract Infection (URTI)
How is an adenovirus keratitis treated?
Topical antibiotic to prevent secondary infection
Mild steroids to speed up recovery if becomes chronic
What sign is distinctive of adenovirus keratitis?
Subepithelial infiltrates
What organisms usually cause keratitis from contact lenses?
Acanthamoeba (commonly from tap water)
Pseudomonas aeruginosa
Who usually gets fungal keratitis?
Farmers/gardeners:
=> history of trauma from vegetation.
What symptoms and signs present in orbital cellulitis?
Painful – especially on eye movements
Proptosis
Pyrexial
What imaging is used to look for orbital abscesses?
CT Scan
What is meant by pre-septal cellulitis?
Only affects top layers of skin
=> not as serious and wont damage any strctures in eye
What is dacryocystitis?
Infection of the lacrimal sac due to an obstruction
What organisms usually cause orbital cellulitis?
Staphylococci Streptococci Coliforms Haemophilus influenzae Anaerobes
How is orbital cellulitis managed?
If restriction of muscles or optic nerve dysfunction then scan
Broad spectrum antibiotics
abscess will require drainage
How does endophthalmitis usually present?
Painful
Decreasing vision
Very red eye
Sight threatening
What is the main cause of endophthalmitis?
Post-surgical (Iatrogenic)
What organisms most commonly cause endophthalmitis?
conjunctival “commensals”
staph epidermidis
What antibiotics are used to treat endophthalmitis and how are they normally delivered?
Antibiotics are injected into vitreous fluid
Intravitreal amikacin/ ceftazidime/ vancomycin`
What organisms are known to cause chorioretinitis?
CMV in AIDS
Toxoplasma gondii
Toxocara canis (worm)
Toxoplasmosis can enter a latent state and reactivate. TRUE/FALSE?
TRUE
especially in immunocompromised individuals
When is toxoplasmosis treated?
If sight threatening, it is treated systemically
Toxocara cannot replicate in humans and is therefore self limiting. TRUE/FALSE?
TRUE
can only replicate in animals such as cats or dogs
How can a Toxocara infection cause vision loss?
Form granulomas which can cause irreversible visual loss
What investigations are used to diagnose eye infections?
Swabs for culture Corneal scrapes in bacterial keratitis Aqueous/vitreous fluid sample for culture in endophthalmitis Microscopy/culture for acanthamoeba Serology for toxoplasma and toxocara
What is grey baby syndrome?
Baby looks grey following chloramphenicol overdose
Why do most eye drop bottles have a recommended “use by” date of 28 days after opening?
Pseudomonas can culture in the bottles after this time
What antiviral is most commonly used in viral conjunctivitis?
Aciclovir
What is used to treat chlamydial conjunctivitis?
topical oxytetracycline
adults may also need oral azithromycin for genital chlamydia infection
Chloramphenicol, fusidic acid and gentamicin are all used to treat what eye infection?
Bacterial conjunctivitis
Other than offloxacin, what antibiotics can be used to treat Bacterial keratitis?
Gentamicin and Cefuroxime
