Conjunctivitis Flashcards
What is blepharitis an infection of?
the eye lid
What is keratitis an infection of?
the cornea
What uveitis an infection of?
the iris, ciliary body and/or choroid
What is chorioretinitis an infection of?
the choroid and retinal layers of the eye
What is endophthalmitis an infection of?
the aqueous and vitreous humor
What are some factors that make someone more prone to eye infections?
immunocompromise
anatomical abnormalitis
dysfunctional tear states
contact lens wearers
What defense mechanism molecules are contained in tears/
secretory IgA and lysozyme
What is the special structure of sIgA and why is this important?
it’s a dimer with a central secreotry piece that protects IgA from being degraded
What sort of immune cells are present in the conjunctiva?
lymphocytes, plasma cells, neutrophils, and mast cells
so you can get antibody and cytokine production
How is blinking an eye defense mechanism?
It inhibits microbial attachment
WHat is the discharge and eye redness from in conjunctivitis?
dilation and congestion of the subepithelial vessles
What are the three general causes of conjunctivitis?
bacterial
viral
allergic
Of the three general causes of conjunctivitis, which are more likely to be bilateral eyes?
allergic is almost always both
bacterial is both 50-75% of the time
viral is bilateral only 30% of the time
What’s tricky about eye redness in bacterial conjunctivitis in older chlidren vs .infants
it’s common in older children, but uncommon in infants and toddlers
If you have an associated acute otitis media and conjunctivitis, is it usually viral or bacterial?
bacterial
What is the general mechanism for allergic rhinoconjunctivitis (hay fever)
- exposure to an antigen
- B cell crease IgE antibodies to the antigen
- the IgE bind to mast cells
- Upon re-exposure to the antigen, it binds tot he IgE
- Cross-linking of the IgE signals degranulation of the mast cells
- Histamines is released into the area
- Histamine increases the permeability of blood capillaries and get swelling and redness in the eyes
What do you use in management of allergic rhinoconjunctivitis/
antihistamines, mast cell stabilizers, NSAIDS
also avoid the antigen in general
Why should steroids be avoided in allergic rhinoconjunctivitis?
they are effective in treating teh allergic rhinoconjuncitbitis itself, but cause complications like glaucoma, cataracts and secondary infection so it’s not worth it
What is the most common virus leading to conjunctivitis in neonates? In the rest of the population?
neonates - HSV1
rest of the population = adenovirus
Besides HSV1 and adenovirus, what are some other viruses that can cause viral conjunctivitis?
coxsackie A24, HSV 2, VZV, EBV, rubella, mumps, influenza
What typically precedes a viral conjunctivitis?
an upper respiratory infection
Where will you particularly see lymphadenopathy in viral conjunctivitis?
preauricular adenopathy
How do you treat viral conjunctivitis?
it’s usually benign and self limited
treat with cold and warm compress and maybe topical vasoconstrictors
What sort of virus is the adenovirus?
it’s a non-enveloped, dsDNA virus
Where does adenovirus cause lytic infection and where does it cause latent infection?
lytic in epithelial cells and latent in lymphoid cells
WHy do some strains of adenoviruses infect the respiratory tract, while some do conjunctive and others do enteri corgans?
the differnt strains ahve different membrane fibers that will attach to different receptors found on different cells thoruhout the body
What 2 adenovirus strains very commonly cause conjunctivitis?
19 and 37
What new test is available to detect adenovirus hexon protein in eye swabs?
adenoplus - you dab and drag is across the lower lid
What is the most common bacteria causing acute bacterial conjunctivitis?
staph aureus
What are some other bacteria that can cause conjunctibitsi?
streptococcus pneumoniae, haemophilus influenze (kids), moraxella, e. coli, pseudomonas aeruginosa
If bacterial conjunctivitis is typically self limiting, why do we treat it with antibiotics?
treating decreases patient morbiditiy and transmission
What is the typical antibiotic used for conjunctivitis?
moxifloxacin solution - it’s the vest cover for both gram positive and gram negatives in this situation
Since moxifloxacin solution is expensive, what oother drug combo is usually given?
trimethoprim and polymyxin B
Moxifloxacin is a fluoroquinolone - wha tis the mechanism of action?
it binds DNA gyrase and disrupt DNA synthesis
What is the mechanism of action for trimethoprim?
it’s blocks DHFR so you don’t have the folate pathway for making nucleotides
What is the mechanism of action for polymyxin B?
It will punch holes in the membranes of gram negative organisms
True or false, you typically do cultures of conjunctivitis to determine the species.
false - usually not necessary - treat epirically wtih broad coverage
only get cultures for recurrent infections, severe infections or no response to treatment
What bacterial causes HYPERACUTE bacterial conjunctibitis
Neisseria gonorrhoaea
(sometimes meninigtidis, but much less often)
What symptoms will you see with a hyperacute bacterial conjunctibitis?
copiois yellow-green discharge - purulent
preauricular adenopathy (even though this is usually with the viral conjunctiitis)
How do you do a gram stain if you’re concerned about hyperacute bacterial conjunctivitis?
you would do one because of the severity
since the eyes are not sterile, you will likely pick up lots of bacteria just from normal flora, so you need to “weed” these out
stain and look for intracellular diplococci
grow on chocolate agar supplemented with vancomycin, colistin, nystatin and trimethroprim to kill off the normal flora and leave the neisseria if it’s there
How do you treat hyperacute bacterial conjunctivitis? Why does it need to be quick?
systemic ceftriazone
it can quickly progress to corneal ulceration and perforation
What is ophthalmia neonatorum?
it’s conjuctibitis or keratoconjunctibitis occurring within the first month of life
What do we do in the US to try to circumvent ophthalmia neonatorum?
we do prophylactic erythromycin ointment in newborn eyes
What type of drug is erythrromycin? How does it work?
it’s a macrolide
it inhibits translation by binding the 23S rRNA of the 50S ribosomal subunit
What is the spectrum for erythromycin?
broa coverage of respiratory pathogens and chlamydia
Resistance to erythromycin is becoming an issue - what are the mechanisms for resistance?
increased efflux
hydrolysis of drug by esterases
methylation of the drug’s binding site
What are the adverse effects of the macrolides like erythromycin?
GI discomfort
hepatic failure
prolonged QT interval
inhibits cyt p450, so check other meds
What bacterial is associated with the leading cuase of blindness worldwide?
chlamydia trachomatis - because you don’t get lasting immunity, recurrent infection is common, resulting in repeat damage to blindness
How do you diagnose chlamydia trachomatis conjunctibitis?
direct fluorescent antibody testing
What is the treatment for chlamydia trachomatis conjunctiitis? What other organism should you be owrried about?
azithromycin
be worries about coinfection with N gonorrhoae
Describe the life cycle of chlamydia trachomatis.
- elementary body enters epithelial cells
- converts to reticular body form in the cell
- replicates with binary fission
- reverts back to elementary body form
- elementary body leaves cell to infect neighbors
What is the isue with interferon-gamma and chlamydia trachomatis?
it can create persistent form of the infeciton which is reactivated when the antibiotic is removed
Which form of the chlamydia trachomatis - elementary or reticulate–will have a rigid otuer membrane?
elementary - it has to be able to survive in the environment
What are the two basic forms of blepharitis?
stye = localized inflammation in eyelash follicle
chalazion = a lipogranuloma plug of a meibomian gland
What is the treatment for blepharitis?
warm compress/massage to open gland
erythromycin ointment for bacterial
What sort of worrisome infection is herpes simplex 1 associated with?
keratoconjunctibitis
Although HSV1 conjunctivitis presents similar to adenovirus at first, what is the distinguishing feature/
it becomes more painful because it often causes scarring of the cornea (often only in one eye)
under fluorescene you’ll see a dendritic formation of the scar
Why should you avoid corticosteroids in treating HSV1 keratoconjunctiitis?
it’s more likely to lead to corneal penetration
If there is corneal involvement of an HSV conjuncivitis, how should you treat it?
topical trifluridine and systemic acyclovir
BOth acyclovir and trifuridine are prodrugs that will act as chain terminators. Why is trifuridine more toxic and therefore only used topically?
Acyclovir is specific to viral-infected cells because it needs thymidine kinase to be phosphorylated, which is only expressedin infected cells
Trifluridine is a pyrimidine analog that is phosphorylated by host kinases, so it’s less specific to the viral infected cells
What are some symptoms besides eye redness you would have with keratitis?
vision defects
photophobia
pain (cornea has lots of nerve endings)
foreign body sensation
What viruses are most commonly associated with keratitis?
HSV1 is the ost common
then adenovirus and VZV
What bacteria are most commonly causing bacterial keratitis?
staph auerus
staph epidermidis
pseudomonas aeruginosa
baccilus cereus
What ameba can cause keratitis?
acanthamoeba - often resides in improperly stores contact lens cleaning fluids
What is the treatment for viral keratitis? bacterial?
viral = trifluridine and acyclovir
bacteria: moxifloxacin eye drops
Who is at the highest risk for pseudomonas aeruginosa eye infections?
contact lens wearers
Why is pseudomonas aeroginosa naturally resistant to many antibiotics?
it can form biofilms
What virulence factor can pseudomonas produce to inhibit mitochondrial enzymes and disrupt ciliary beating in keratitis?
a blue pigment called pyocyanin
What virulence factors will break down the corneal epithelium in pseudomonas keratitis?
elastase and alkaline protease
What are the two types of uveitis?
iritis - anterior uveitis
chorioretinitis - posterior uveitis
How are the symptoms for iritis and chorioretinitis different?
iritis - photophobia, pain, decreased acuity
chorioretinitis - floaters, no pain (more common)
Why is chorioretinitis frequency a manifestation of systemic disease?
It’s affecting the retinal arteries and it’s usually blood borne to that area from somewhere else in the body
What two congenital infections common cause chorioretinitis in neonates?
toxoplasma
CMV
What are two worm parasitic infections that can cause eye infections - chorioretinitis in particular?
toxocara cani
onchocerca volvulus (river blindness from sand flies)
Who typically gets endophthalmitis - it’s rare.
people who have had recent intraocular surgery like cataract surgery.
the agent is from normal flora like pseudomonas, staph, or candida
How do you treat endophthalmitis?
you inject fluoroquinoloe or vancomycin into the eye
