microbiology of the eye Flashcards
What is:
conjunctivitis
keratitis
endophthalmitis
- 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?
Symptoms: • Sticky red eyes • Pus • papillae • foreign body sensation – gritty eye • discharge – sticky eye • Itch = allergy • vision unaffected
Signs: • 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 REFER ALL TO OPHTH.
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: -chloramphenicol -fusidic acid -gentamicin cover?
chloramphenicol
(treats most bacteria except Pseudomonas aeruginosa)
fusidic acid
(treats Staph. aureus)
gentamicin
(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
Treatment:
• 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
Symptoms:
- Pain+ – needle like severe – i.e. if corneal nerves intact _ note corneal sensation is affected by herpes viruses
- Photophobia
- Profuse lacrimation
- Vision may be reduced
- Red eye - circumcorneal
Signs:
- Redness – circumcorneal
- Corneal reflex (reflection abnormal)
- Corneal opacity
- Staining with fluorescein
- hypopyon
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
Peripheral:
-rheumatoid arthritis
-hypersensitivity e.g. marginal ulcers
(+ rarely Wegener’s granulomatosis, polyarteritis etc)
what is the management of bacterial keratitis?
General:
- 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
Investigation:
- 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
Treatment
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)
