microbiology of the eye Flashcards Preview

Opthalmology > microbiology of the eye > Flashcards

Flashcards in microbiology of the eye Deck (29):

What is:

• Conjuctivitis: inflammation of conjunctiva
• Keratitis: inflammation of the cornea
• Endophthalmitis: entire globe inflammation


What are the symptoms of conjunctivitis? what are the signs of conjunctivitis?

• Sticky red eyes
• Pus
• papillae
• foreign body sensation – gritty eye
• discharge – sticky eye
• Itch = allergy
• vision unaffected

• Red eye - note pattern of redness – diffuse more towards the fornices
• Discharge - serous or mucopurulent
• Papillae or Follicles
• Sub conj. haemorrhage
• Chemosis = oedema
• Pre-auricular glands (if viral)


What organisms cause bacterial conjunctivitis in neonates?

In neonates:
⎯ Staph aureus
⎯ Neisseria gonorrhoeae
⎯ Chlamydia Trachomatis


What organisms causes bacterial conjunctivitis in all ages?

Other ages:
⎯ Staph. Aureus
⎯ Strep. Pneumonia
⎯ Haemophyilus influenzae (esp. in children)


What organisms causes bacterial conjunctivitis in contact lens wearers?

Contact lenses:
⎯ Acanthamoeba
⎯ Pseudomonas aeruginosa

Could still be staph. Aureus but these organisms specific to contact lenses
Send off lens and container lens is kept in


How is bacterial conjunctivitis treated?

• Swab
• Topical antibiotic usually chloramphenical qds
• Drops vs ointment
• Avoid chloramphenicol if history of aplastic anaemia or allergy
• Be aware of chloramphenicol allergy if worsening symptoms

Usually bacterial conjunctivitis is self limiting and will clear up in about 14 days but topical a.biotics clear it faster


What organisms do:
-fusidic acid

(treats most bacteria except Pseudomonas aeruginosa)

fusidic acid
(treats Staph. aureus)

(treats most Gram negative bacteria including coliforms, Pseudomonas aeruginosa)


What organisms cause viral conjunctivitis?

⎯ Adenovirus
⎯ Herpes Simplex
⎯ Herpes Zoster


What is seen clinically and how is adenoviral conjunctivits managed?

• V. little discharge
• Eyes watering

• Normally don't need antibiotics – self limiting
• Can give them for secondary infection though


How is herpetic conjunctivitis treated?

Use topical +/- oral acyclovir (antiviral)


Which nerve has been involved if the tip of the nose is affected in herpes zoster conjunctivitis?

If this has reached the tip of the nose, V1 has been involved.


Describe the clinical features of chlamydial conjunctivitis?

• Often chronic history – gradual creeping up
• Unresponsive to treatments
• Suspect in bilateral conjunctivitis in young adults
• May or may not have symptoms of urethritis, vaginitis
• Need contact tracing
• ‘Follicular’ conjunctivitis – looks like little rice grains
• Can cause subtarsal scarring underneath upper lid


What is the treatment of chlamydial conjunctivitis

topical oxytetracycline

(but adults may also need oral azithromycin treament for genital chlamydia infection)


Describe the clinical features of keratitis
what are the symptoms? what are the signs?

In the cornea the keratin layers are arranged so the structure is transparent. When it becomes inflamed = white

This shows a little ulcer and the hypopyon – which is the white blood cells settling at the bottom of the aqueous chamber

‘Eye fine on Monday, like this on Tuesday’

Usually in association with other corneal pathology or contact lens wear

-Pain+ – needle like severe – i.e. if corneal nerves intact _ note corneal sensation is affected by herpes viruses
-Profuse lacrimation
-Vision may be reduced
-Red eye - circumcorneal

-Redness – circumcorneal
-Corneal reflex (reflection abnormal)
-Corneal opacity
-Staining with fluorescein


Keratitis can be central (infective) or peripheral (autoimmune) What organisms can cause microbial keratitis? what is done for diagnosis?
-what can cause peripheral keratitis?

• Bacteria
• Viruses
⎯ herpes
⎯ adenovirus
• Funghi
Do a corneal scrape for diagnosis

-rheumatoid arthritis
-hypersensitivity e.g. marginal ulcers
(+ rarely Wegener’s granulomatosis, polyarteritis etc)


what is the management of bacterial keratitis?

-Identify cause – ‘corneal scrape’ for gram stain and culture
-Antimicrobial if bacterial infection
-Antiviral if herpetic: Aciclovir ointment 5 x day
-Anti-inflammatory if autoimmune: Oral / topical steroids

-Swab under anaesthetic and then admit as in patient and give eye drops every hour for 48 hrs
-Daily review

Treatment of bacterial keratitis
• A 4-quinolone (Ofloxacin)
(treats most Gram negative bacteria including coliforms, Pseudomonas aeruginosa, Haemophilus influenzae. Not active vs. Strep. pneumoniae)
• Gentamicin and cefuroxime
(the combination will treat most Gram positive and Gram negative organisms)


What is seen clinically in herpetic keratitis? What is the treatment? what not to give?

This shows a ‘dendritic ulcer’ classic of herpetic keratitis

Painful – ‘can’t open eyes’ so put anaesthetic in to examine eye

Can recur, but as recurs becomes less painful as sensation to cornea decreases – sight still affected

Topical acyclovir 5 times a day
Sometimes can debride area using cotton bud under anaesthetic
If give steroid the virus can eat away at eye = corneal melt and perforation


what is seen clinically in adenoviral conjunctivits and what is the treatment?

• Bilateral
• Usually follows an URTI – can follow conjunctivitis
• Contagious
• Can give topical AB to prevent secondary infection
• May affect vision
• Can require steroids to speed up recovery if becomes chronic


What are the clinical features of fungal keratitis?

• More indolent course than microbial keratitis
• Usually a history of trauma from vegetation.
• Takes a long time to heal


What are the clinical features of orbital cellulitis?

• Painful – especially on eye movements (horizontal muscles are painful)
• Proptosis
• Often associated with paranasal sinusitis (usually from sinuses-ENT deal)
• Pyrexial
• Sight threatening
• Cared for by ENT and Ophthalmology
• CT scan to identify orbital abscesses
Swelling within the orbit can press on diff. structures e.g. nerves/muscles


How can orbital cellulitis arise?

• Direct extension from sinus
• Extension from focal orbital infection (infected chalazion, dacryocystitis)
• Post-operative
• Need to differentiate between preseptal and orbital
Behind septum – more serious as can cause space occupying lesion
Infront of septum – just need antibiotics


What organisms can cause orbital cellulitis?

• Staphylococci
• Streptococci
• Coliforms
• Haemophilus influenzae
• anaerobes


What is the management of orbital cellulitis?

• If any suggestion there is restriction of muscles or optic nerve dysfunction then scan
• Broad spectrum AB and monitor closely
• Sometimes an abscess will require drainage


What is endophthalmitis? how can this arise? what is seen clinically?

• Devastating infection inside of the eye
• Post-surgical or endogenous
• Painful +++, with decreasing vision
• Very red eye
• Sight threatening

(Difficult to get antibiotics into eye – can’t use systemic, eye is bad at fighting infection)


what organisms can causes endopthalmitis? what is the treatment?

• Often conjunctival “commensals”
• Most common is staph epidermidis

Intravitreal amikacin and vancomycin and topical antibiotics
(also aspirate some fluid to send to microbio. for culture)


What is chorioretinitis?

Chorioretinitis is an inflammation of the choroid (thin pigmented vascular coat of the eye) and retina of the eye. It is a form of posterior uveitis


What can cause chorioretinitis?

• Toxoplasma gondii
• Toxocara canis (worm)


-what is seen clinically?
-how is this diagnosed?

• Protozoan infection toxoplasmosis gondii
• Mild flu like illness
• Rarely causes any further problems
• In immunocompetent patients it enters latent phase with cysts forming
• Very common- 10% of USA sample had toxoplasmosis specific IgG
• Can reactivate
• Requires systemic treatment if sight threatening
• Do serology to diagnose


-what is this?
-how is this treated?
-what is a complication?
-how is this diagnosed?

• Parasitic nemotode (roundworm)
• Affects cats or dogs
• Unable to replicate in humans
• Remains an immature form of the worm (larvae)
• Often self limiting as they cannot replicate
• Form granulomas which can cause irreversible visual loss - This is more serious as can transfer to fetus
• Do serology to diagnose