Microbiology in Ophthalmology Flashcards by Olivia McNee

What causes bacterial conjunctivitis in under 2’s?

Staph Aureus
Neisseria gonorrhoea
Chlamydia thrachomatis

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What causes bacterial conjunctivitis in adults?

Staph aureus
Strep pneumonia
Haemophilus influenze

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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

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What should you be wary about regarding chloramphenicol?

Avoid if aplastic anaemia

Allergy- if patient describes worsening symptoms

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Describe adenovirus conjunctivitis

Fairly common- ‘pink eye’

Most of the time- red watery eye

Self-limiting

Contagious

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Describe herpes simplex conjunctivitis

Found in patients if they have vesicles around the eye

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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

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What is keratitis?

Further back in the eye and less common than conjunctivitis

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Describe the history of chlamydial conjunctivitis?

Often chronic history

Unresponsive to treatments

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When should you suspect chlamydial conjunctivitis?

Bilateral conjunctivitis in young adults

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What are the other features of chlamydial conjunctivitis?

urethritis, vaginitis

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What features of the eyes suggest chlamydial conjunctivitis?

Follicular change, this can cause scarring

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What is a hypopyon?

white cells in the cornea causing white deposit

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How is bacterial keratitis with hypopyon treated?

Admission for hourly drops and daily review

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How serious is bacterial keratitis with hypopyon?

Serious, sight threatening

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What is bacterial keratitis with hypopyon associated with?

Co-morbid condition; rheumatoid, contact lenses

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Which viruses cause keratitis?

Herpes

Adenovirus

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Describe the symptoms in herpetic keratitis

Pain

Can’t open eye, no history of trauma

Reduced corneal sensation

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How should herpetic keratitis be treated?

Anaesthetic drops and antiviral

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How should herpetic keratitis NOT be treated?

Steroids- cause a corneal melt and perforation

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Describe the symptoms in keratitis caused by adenovirus

Poor vision
Conjunctivitis too
Contagious
follows a URTI

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How is keratitis caused by adenovirus treated?

With topical antibiotics to prevent secondary infection - topical stewards if chronic

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What does a dendritic ulcer look like and when is it seen?

Branching tree

Herpetic viral keratitis

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When is fungal keratitis seen?

Very rare

Contact lenses

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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