Microbiology in Opthamology Flashcards
what are the 3 causes of bacterial conjunctivitis in neonates?
staph aureus
Neisseria gonorrhoea
chlamydia trachomatis
all cases in neonates must be referred to ophthalmology
3 causes of bacterial conjunctivitis in other ages?
staph aureus
strep pneumoniae
haemophilus influenzae (esp in children)
how is bacteria conjunctivitis managed?
swab topical antibiotic (usually chloramphenicol) drops vs ointment
when must chloramphenicol be avoided?
if history of aplastic anaemia or allergy
be aware that allergy may be present if symptoms worsen
3 causes of viral conjunctivitis?
adenovirus
herpes simplex
herpes zoster
what may indicate a chlamydial conjunctivitis?
chronic history
unresponsive to treatments
suspect in bilateral conjunctivitis in young adults
may or may not have symptoms of urethritis or vaginitis
need contact tracing
what may chlamydial conjunctivitis look like?
follicles like tiny grains of rice in the conjunctiva
can cause tubtarsal scarring
3 causes of microbial keratitis?
bacteria
viruses
fungi
what does bacterial keratitis look like?
level of white within the cornea due to mixing up of precisely arranged collagen fibres as a result of swelling, inflammation etc
what is a hypopyon?
a leukocytic exudate, seen in the anterior chamber, usually accompanied by redness of the conjunctiva and the underlying episclera
how is bacterial keratitis managed?
need admission for hourly drops
daily review
usually in association with other corneal pathology or contact lens wearer
name 2 causes of viral keratitis?
herpes
adenovirus
bacterial vs viral keratitis?
bacterial = usually have an underlying pathology associated viral = can just happen in otherwise healthy eyes
how might herpetic keratitis present?
dendritic ulcer
shows under blue light
incredibly painful (especially the first time)
can be recurrent which can eventually result in reduced corneal sensation
how is herpetic keratitis managed?
NEVER GIVE STEROIDS
- can cause a corneal melt and perforation
??? (flurosine?)
how might adenoviral keratitis present?
subepithelial infiltrates bilateral usually after URTI may affect vision contagious
how is adenoviral keratitis managed?
can give topical AB to prevent secondary infection
can require steroids to speed up recovery if it becomes chronic
what is acanthamoeba?
type of fungal keratitis
- pseudomonas aeruginosa
usually occurs in contact lens wearer
more indolent course than microbial keratitis
ususally a history of trauma from vegetation (e.g gardener)
takes a long time to heal
what are the features of orbital cellulitis?
painful (esp. on eye movements) proptosis associated with paranasal sinusitis pyrexial sight threatening swollen, red, puffy area around the eye
how is orbital cellulitis managed?
cared for by ENT and ophthalmology
CT scan to identify orbital abscesses if any suggestion of a restriction of muscles or optic nerve dysfunction (ask about red colour vision, follow finger etc)
broad spectrum AB and close monitoring
abscesses will require drainage
what can cause orbital cellulitis?
direct extension from sinus
extension from focal orbital infection
post-operative
what organisms can cause orbital cellulitis?
staph strep coliforms haemophilus influenzae anaerobes
what is endophthalmitis?
devastating infection inside of the eye
what can cause endophthalmitis?
post surgical (most common - leads to sudden blindness) endogenous (spread from systemic infection in other areas of the body like endocarditis)
how does endophthalmitis present?
very painful
decreasing vision
very red eye
sight threatening
what organisms usually cause endophthlamitis?
often conjunctival commensals
most common = staph epidermidis
how is endophthalmos managed?
intravitreal - amikacin - ceftazidime - vancomycin - topical antibiotics systemic antibiotics
3 causes of chorioretinitis?
CMV in AIDS
Toxoplasma gondii
Toxocara canis (worms)
what does CMV chorioretinitis look like?
many areas of exudate and haemorrhages in the retina
where is toxoplasma gondii likely to come from?
cats and raw meat
how does toxoplasmosis infection present?
mild flu like illness
can enter latent phase with cysts forming in an immunocomprimised patient
rarely causes further problems in healthy people
how is toxoplasmosis managed?
can be left alone
requires systemic treatment is sight threatening
can reactivate
what is toxocara?
parasitic nematode (roundworm) affects cats and dogs, unable to replicate in humans but remains an immature form of the worm
what do toxocara do in the body?
often self limiting as they cannot replicate
form granulomas which can cause irreversible visual loss
how are bacterial, chlamydial and viral eye infections diagnosed?
swabs for culture
how is bacterial keratitis diagnosed?
corneal scrapes
how is endophthalmitis diagnosed?
aqueous/vitreous for culture
how is acanthamoeba diagnosed?
microscopy/culture
how is toxoplasma and toxocara diagnosed?
serology
what are the 3 broad categories of antibiotics?
inhibit protein synthesis
inhibit cell wall synthesis
inhibit nucleic acid synthesis
what is the most commonly used topical antibiotic and what does it do?
chloramphenicol
inhibits peptidyl transferase enzyme which stops bacterial protein being made
bacteriocidal for strep and haemophilus
bacteriostatic for staph
how can chloramphenicol be delivered and what are 3 possible side effects?
ointment or dops must be kept in the fridge side effects: - allergy - irreversible aplastic anaemia (rare) - grey baby syndrome (if too much given?)
name 2 types of antibiotics which inhibit cell wall synthesis and how they work
penicillins and cephlasporins
both have a common B lactam ring
B lactam ring inhibits enzyme which makes bacterial cell wall
without cell wall, bacteria die
name an antibiotic which inhibits nucleic acid synthesis can how
quinolones (e.g ofloxacin)
inhibits DNA gyrase (an enzyme which compresses bacterial DNA into supercoils)
inhibition of DNA gyrase leads to unwinding of supercoils and cell death
name 3 common treatments for bacterial conjunctivitis
chloramphenicol = treats most apart from pseudomonas
fusidic acid = treats staph aureus
gentamicin = treats gram -ves - e.g coliforms, pseudomonas)
name a commonly used antiviral and how it works
acyclovir inhibits viral DNA synthesis base analogue (mimics guanine) topical and systemic used for dendritis ulcers of the cornea
how is chlamydial conjunctivitis managed?
topical oxytetracycline
- adults may also need oral azithromycin for genital chlamydia infection
name 2 treatments for bacterial keratitis
a 4-quinolone (ofloxacin) = treats most gram -ves but not strep pneumonia
gentamicin and cefuroxime = treats most gram +ve and -ves)
