Microbiology in Ophthalmology Flashcards
what is an infection of the conjunctiva called
conjunctivitis
what is an infection of the cornea called
keratitis
what is an infection of the entire eye called
endophthalmitis
what bacteria causes bacterial conjunctivitis in neonates
staph azures
neisseria gonorrhoea
chlamydia trachoma’s
what bacteria causes bacterial conjunctivitis in all other ages
staph aures
strep pneumonia
haemophilus influenza (especially in children)
how do you treat bacterial conjunctivitis
swab
topical antibiotic - chloramphenicol
drops/oitment
when should you avoid using chloramphenicol in the treatment of bacterial conjunctivitis
history of aplastic anaemia or allergy
what viruses cause viral conjunctivitis
adenovirus
herpes simplex
herpes zoster
key difference in the presentation of viral vs bacterial conjunctivitis
bacterial - pussy discharge
how does chlamydial conjunctivitis tend to present
chronic history
unresponsive to treatments
bilateral conjunctivitis in young adults
may or may not have vaginitis/urethritis
Looks like lots of little bumps under the eye lids- these can cause scarring to cornea so must be treated
what can cause keratitis
bacteria
viruses
fungi
what are the characteristics of bacterial keratitis
v rare
looks bad - v serious
white lump on cornea
level of white cells in the eye
that is the treatment for bacterial keratitis
hourly drops - even over night so needs admission
main risk factors for bacterial keratitis
contact lens wearers
other corneal pathology
what viruses can cause viral keratitis
herpes
adenovirus
characteristics of herpes keratitis
a dendritic ulcer on the eye - looks like bolt of lightening
v painful, recurrent
what happens if herpes keratitis is treated with steroids
can cause corneal melt and perforation of the cornea
characteristics of adenovirus keratitis
bilateral
follows URTI
contagious
sub epithelial infiltrates
treatment for adenovirus keratitis
topical antibiotic to prevent secondary infection (bacterial keratitis can be caused by other corneal pathologies)
can require steroids to speed up recovery if it becomes chronic
what fungi can cause keratitis
acanthamoeba
pseudomonas aeruginosa
what is a hypopyon
inflammatory infiltrate built up in the eye - looks like a white line
characteristics of fungal keratitis
not as painful as bacterial
history of trauma from vegetation
takes long time to heal
what is orbital cellulitis
inflammation of eye tissues due to infection spread from the sinuses into the orbit
characteristics of orbital cellulitis
painful - especially on eye movements
often associated with paranasal sinusitis
can compromise the optic nerve
swollen puffy red eye - skin around the eye is v swollen
why is it important to differentiate between preseptal an orbital
because orbital can cause compartment syndrome
what organisms cause orbital cellulitis
staph strep coliforms haemophilus influenzae anaerobes
treatments for orbital cellulitis
if there’s any signs of restriction of muscles or optic nerve dysfunction - scan
give broad spectrum AB and monitor closely
sometimes abscesses need drainage
what is endophthalmitis
rare and devastating infection inside the eye
v painful with decreasing vision - sight threatening
what causes endophthalmitis
post surgical or endogenous ( if they have a systemic infection clumps of bacteria can get into the eye)
treatment for endophthalmitis
difficult to treat infection inside eye - cut off from immune system
intravitrial
amikacin/ceftazimide/vancomycin
systemic antibiotics given as well
causative organisms of endophthalmitis
conjunctival commensals
most common - staph epidermidis
what is chorioretinitis
infection of the retina and choroid
what causes chorioretinitis
cytomegalovirus seen in patents with AIDS
Toxoplasma gondii
toxocara Canis (worm)
characteristics of toxoplasma gondii chorioretinitis
protozoa get it from cats and raw meat mild flu like illness rarely causes any other problems enters the latent phase with cysts forming needs treatment if life threatening
characteristics of toxocara Canis
worm
get it from cats and dogs
unable to replicate in humans
remains an immature form of worm (larvae)
self limiting as cannot replicate
form granulomas which can cause irreversible vision loss
investigations for conjunctivitis
swabs for culture - bacterial, chlamydial, viral
investigation for bacterial keratitis
corneal scape
investigation for endophthalmitis
aqueous/vitreous culture
investigation for ancanthamoeba
microscopy/culture
type of keratitis
investigation for toxoplasma and toxocara
serology
what are the 3 main ways antibiotics kill cells
inhibit cell protein synthesis
inhibit cell wall synthesis
inhibit nucleic acid synthesis
what is the most commonly used antibiotic for eye infections
chloramphenicol
how does chloramphenicol act
inhibits peptides transferase enzyme (therefore inhibits bacterial protein synthesis)
what organisms is chloramphenicol bactericidal for
strep
haemophilus
what organism is chloramphenicol bacterostatic for
staph
side effects of chloramphenicol
allergy
irreversible aplastic anaemia (v r are)
grey baby syndrome
what antibiotics inhibit cell wall synthesis
penicillins and cephalosporins - have common B lactic ring which inhibits the enzyme which makes the bacterial cell wall
what antibiotics inhibit nucleic acid synthesis
quinolone eg. ofloxacin inhibit enzymes that compress bacterial DNA into supercoils
inhibition of DNA gyrase leads to unwinding of DNA coils and cell death
what is a common contaminate of eyedrops bottles
pseudomonas - eyedrop preservatives keep them clean of contaminants but only last 4 weeks
antibiotics for bacterial conjunctivitis
chloramphenicol
(treat most except pseudomonas)
fusdic acid (treats staph aures)
gentamicin (treats gram -ve bacterias including pseudomonas)
what antivirals are used in viral eye infections
Aciclovir
used for dendritic ulcers of the cornea
what antibiotic is used for chlamydial conjunctivitis
topical oxytetracycline
antibiotics for bacterial keratitis
Ofloxacin
-treats most gram -ve but not strep pneumonia)
gentamicin and cefuroxime (combination treats most gram + and -)
