Microbiology Flashcards
Give two examples of gram positive cocci
Strep
Staph
Give an example of gram negative
- Cocci
- Cocci-bacilli
- Bacilli
Gram negative
- Cocci – Neisseria
- Cocci-bacilli – H. influenze
- Bacilli – pseudomonas
Which pathogens should you suspect in neonatal conjunctivitis?
Most likely from the birth canal, i.e. STIs - Staph aureus - Neisseria gonorrhoeae - Chlamydia trachomatis Refer all cases to ophthalmology.
Which pathogen should you think of in children with conjunctivitis?
H. influenzae
How should you treat bacterial conjunctivitis?
What if theres corneal abrasion?
Chloramphenicol eye drops
If corneal abrasion, ointment can be quite soothing
When should you avoid chloramphenicol?
History of aplastic anaemia or allergy
What should you consider in a patient with worsening bacterial conjunctivitis despite treatment?
Chloramphenicol allergy - may become more itchy as well
What is viral conjunctivitis commonly preceded by?
How does it present?
URTI
Very, very red eyes
Which three pathogens should you consider in viral conjunctivitis?
Adenovirus
Herpes simplex – looks like small white pustules around the eye
Herpes zoster
Which nerve is affected in herpes zoster of the eye?
CN V1 - ophthalmic division of trigeminal nerve
If the tip of the nose is affected by herpes zoster infection, what else is likely to be involved?
Which nerve has been affected?
Eye - refer to ophthalmology
Nasociliary nerve
Treatment of herpes zoster infection?
Oral acyclovir asap
Chronic history of conjunctivitis which isn’t too bad - which pathogen?
What might be seen on examination?
Chlamydia
Exaggerated lymphatic response - looks like rice grains on the inside of the lid
Why does corneal infection need urgent treatment?
If you have infection on cornea it can work its way straight through to the back of the eye – very difficult to treat.
What does microbial keratitis look like on examination?
Big white lesion on eye – shine cobalt blue on it.
White line along the bottom = white cells within the anterior chamber – inflammatory process is so severe that there is intra-ocular inflammation.
What is a hypopyon and which condition is it associated with?
Hypopyon = presence of leukocytes in the anterior chamber of the eye.
Microbial keratitis
Investigation of microbial keratitis?
Put local anaesthetic eye drops in, take scalpel and scrape surface of eye – send it off for
- Microscopy
- Culture
Treatment of bacterial keratitis?
Admit patient – antibiotic eye drops every hour for 48 hours at least.
What does herpes simplex keratitis cause on the cornea?
Dendritic type ulcer
This is very painful and can result in reduced corneal sensation
What should you not treat viral keratitis with?
Steroids - can cause a corneal melt and perforation of the cornea
How should viral keratitis be treated?
Topical acyclovir 5x per day
What can you see on examination of adenoviral keratitis?
Subepithelial infiltrates - looks like little white dots on the cornea
Treatment of adenoviral keratitis?
- Contagious – tell patient to use different towels from others in the house etc
- Can give topical AB to prevent secondary infection
- Patients often have slightly reduced vision
- Can require steroids to speed up recovery if becomes chronic
Give some features of fungal keratitis
- More indolent course than microbial keratitis
- Usually a history of trauma from vegetation
- Takes a long time to heal
- Can get hypopyon
Give some clinical features of orbital cellulitis
Which syndrome is a risk and what is the first clinical feature of this?
- Painful – especially on eye movements
- Proptosis
- Often associated with paranasal sinusitis
- Pyrexial
It is sight threatening and can lead to orbital compartment syndrome. One of the first things to go is colour vision.
Investigation of orbital cellulitis?
CT scan
What is endophthalmitis?
- What is the most common preceding event?
- Symptoms?
Devastating infection inside of the eye
- Post surgical
- Painful +++, with decreasing vision
- Very red eye
- Sight threatening
What is the most common pathogen in endophthalmitis?
Staph epidermis
How is endophthalmitis treated?
In theatre suck out some of the gel of the eye and inject intravitreal amikacin and vancomycin and topical antibiotics. Send the gel off to the microbiology lab.
Which pathogen is associated with endophthalmitis in HIV?
Cytomegalovirus
Which microbiology infections are done in:
- Bacterial keratitis
- Endophthalmitis
- Acanthomoeba
- Toxoplasma/toxocara
- Corneal scrapes in bacterial keratitis – only done by microbiologist
- Aqueous/vitreous for culture in endophthalmitis
- Microscopy/culture for acanthamoeba – tell patient to bring their contact lens case
- Serology for toxoplasma and toxocara
How does chloamphenicol work?
- Inhibits peptidyl transferase enzyme (therefore stops bacterial protein being made)
- Bacterocidal for strep and haemophilus
- Bacterostatic for staph
Give three side effects of chloramphenicol
- Allergy
- Irreversible aplastic anaemia (rare : 1 in 40,000)
- Grey baby syndrome
What is dacrocystitis?
Infection of the lacrimal sac, secondary to obstruction of the nasolacrimal duct at the junction of lacrimal sac.
Antibiotic for corneal ulcers?
Ofloxacin
Which bacteria does chloramphenicol not treat?
Pseudomonas aeruginosa
Which drug is used for staph aureus?
Fusidic acid
Which pathogens does gentamicin treat?
Gentamicin treats most Gram negative bacteria including coliforms, Pseudomonas aeruginosa.
How is chlamydial conjunctivitis treated?
Topical oxytetracycline
but adults may also need oral azithromycin treatment for genital chlamydia infection
