Microbiology Flashcards
How does bacterial conjunctivitis present?
Red eye and purulent discharge
Name three common pathogens in neonatal conjunctivitis
Staph aureus
Neisseria gonorrhoea
Chlamydia trachomatis
What should be done if you see neonatal conjunctivitis?
Urgent ophthalmology referral
In other age groups what pathogens cause bacterial conjunctivitis?
Staph aureus
Strep pneumoniae
H.influenza (especially kids)
How is bacterial conjunctivitis managed?
Swab Topical antibiotics (chloramphenicol QDS)
When is chloramphenicol contraindicated?
Patients with a history of aplastic anaemia or patients with a chloramphenicol allergy
What are the two types of chloramphenicol and what is the disadvantage of each?
Drops need to be kept in the fridge
Ointment can cause visual problems
Name three causes of viral conjunctivitis
Adenovirus
Herpes Simplex
Herpes Zoster
Describe adenoviral conjunctivitis
Pink eye, usually after URTI is highly contagious but does not require treatment
What often occurs with herpes simplex conjunctivitis?
Associated skin rash
What is Hutchison Sign and why does this occur?
Herpes zoster of the nasociliary branch of the ophthalmic division of the trigeminal nerve causes vesicles on the tip/side of nose and indicates eye involvement
How does chlamydial conjunctivitis present?
Chronic history of conjunctivitis which is unresponsive to treatment - usually bilateral in young adults, low grade red eye but no discharge.
What is the classic sign of chlamydial conjunctivitis?
Follicles on inner eyelid
What can chlamydial conjunctivitis cause?
Sub tarsal scarring
What is keratitis?
Infection of the cornea
How does the cornea look when infected?
Cloudy as bacteria dislodges the natural arrangement
Define hypopyon
Pus behind the eye
How is bacterial keratitis managed?
Scraping for culture
Admission for hourly drops
What is the serious complication of bacterial keratitis?
Perforation
How does keratitis caused by herpes present?
Very painful and often recurrent infection with dendritic ulcers
What stain can be used to see dendritic ulcers?
Flurocein
What can recurrent herpes keratitis lead to?
Reduced corneal sensation
What must not be given in herpes keratitis and why?
Steroids - risk of corneal melt and perforation
How does adenovirus cause keratitis?
Autoimmune reaction post URTI
What does adenovirus keratitis look like?
Bilateral subepithelial infiltrates and blurred vision
Why are antibiotics given in adenovirus keratitis?
To prevent secondary infection
What may be required if adenovirus keratitis becomes chronic?
Steroids
Describe keratitis caused by fungi
Not as bad as bacterial, takes a few weeks to develop and usually has a history of trauma from vegetation
How will fungal keratitis present?
Well defined ulcer that takes a long time to heal
What infections are caused by contact lenses?
Acanthamoeba Pseudomonas aeruginosa (very painful)
What is orbital cellulitis and how does it occur?
Pus in the orbit pushes the eye forward usually a direct extension from the sinus/focal orbital infection.
How does a patient with orbital cellulitis present?
Proptosis, severe pain on movement, extremely unwell, pyrexic, well demarcated erythema
Why is orbital cellulitis sight threatening?
It can cause damage to the optic nerve
Name the pathogens associated with orbital cellulitis
Staphylococci Streptococci Coliforms H.influenza Anaerobes
What investigation can be done on a patient with suspected orbital cellulitis?
CT scan
What is the difference between preseptal and orbital cellulitis?
Preseptal - no compression of the nerve, less serious
Orbital - emergency, sight threatening compression of the nerve
How is orbital cellulitis treated?
Broad spectrum antibiotics and drainage
What is endophthalmitis?
Infection of the whole globe
How does endophthalmitis present?
Usually 48 hours post surgery patients lose sight, extremely painful and red eye, systemically unwell
How does endophthalmitis occur?
Blood retinal barrier is perforated resulting in infiltration of commensals such as staph epidermis
What surgery is endophthalmitis a complication of?
Cataract surgery
How is endophthalmitis managed?
Needle into vitreous to take culture and inject antibiotics
Define chorioretinitis
Infection of the choroid and retina
Name three causes of chorioretinitis
- CMV in AIDS and HSV
- Toxoplasmosis Gondii
- Toxocara Canis
Describe toxoplasmosis gondii
Protozoan infection from cats and raw meat that causes a mild flu like illness and rarely further problems. Can sit in the eye in the latent phase but can reactivate
What happens when toxoplasmosis gondii reactivates?
It interferes with vision and requires systemic therapy
Describe toxocara canis
Roundworm affects cats/dogs but is unable to replicate in the human body so remain immature larvae, fairly self limiting
What is the serious compilation of toxocara canis?
Granuloma formation and irreversible visual loss
State four methods of diagnosis for eye infections
- swabs
- corneal scrapes
- aqueous/vitreous culture
- serology
What is dacrocystitis?
Lacrimal sac outflow is occluded which leads to bacterial proliferation
How does chloramphenicol work?
Inhibits protein synthesis
Is chloramphenicol bacteriostatic/cidal?
Bactericidal - strep and haemophillus
Bacteriostatic - staph
What can be used for staph infections which don’t respond to chloramphenicol?
Fusidic acid
What can chloramphenicol cause?
Aplastic anaemia
Grey Baby Syndrome
What quinolone is commonly used in keratitis?
Ofloxacin
How do quinolones work?
Inhibit DNA synthesis
Why should use of ofloxacin be monitored closely?
Antibiotic resistance
What bacteria is a common contaminant?
Pseudomonas
What can be used to treat gram negative bacteria?
Gentamicin
How does acyclovir work?
Mimics G base to inhibit DNA synthesis - used to treat dendritic corneal ulcers
What is the treatment for chlamydial conjunctivitis?
Oxytetracycline (adults may also need treatment for genital chlamydia)
