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Neuro Block 3 > Conjunctivitis > Flashcards

Conjunctivitis Flashcards

1
Q

What is blepharitis an infection of?

A

the eye lid

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2
Q

What is keratitis an infection of?

A

the cornea

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3
Q

What uveitis an infection of?

A

the iris, ciliary body and/or choroid

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4
Q

What is chorioretinitis an infection of?

A

the choroid and retinal layers of the eye

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5
Q

What is endophthalmitis an infection of?

A

the aqueous and vitreous humor

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6
Q

What are some factors that make someone more prone to eye infections?

A

immunocompromise

anatomical abnormalitis

dysfunctional tear states

contact lens wearers

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7
Q

What defense mechanism molecules are contained in tears/

A

secretory IgA and lysozyme

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8
Q

What is the special structure of sIgA and why is this important?

A

it’s a dimer with a central secreotry piece that protects IgA from being degraded

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9
Q

What sort of immune cells are present in the conjunctiva?

A

lymphocytes, plasma cells, neutrophils, and mast cells

so you can get antibody and cytokine production

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10
Q

How is blinking an eye defense mechanism?

A

It inhibits microbial attachment

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11
Q

WHat is the discharge and eye redness from in conjunctivitis?

A

dilation and congestion of the subepithelial vessles

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12
Q

What are the three general causes of conjunctivitis?

A

bacterial

viral

allergic

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13
Q

Of the three general causes of conjunctivitis, which are more likely to be bilateral eyes?

A

allergic is almost always both

bacterial is both 50-75% of the time

viral is bilateral only 30% of the time

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14
Q

What’s tricky about eye redness in bacterial conjunctivitis in older chlidren vs .infants

A

it’s common in older children, but uncommon in infants and toddlers

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15
Q

If you have an associated acute otitis media and conjunctivitis, is it usually viral or bacterial?

A

bacterial

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16
Q

What is the general mechanism for allergic rhinoconjunctivitis (hay fever)

A
  1. exposure to an antigen
  2. B cell crease IgE antibodies to the antigen
  3. the IgE bind to mast cells
  4. Upon re-exposure to the antigen, it binds tot he IgE
  5. Cross-linking of the IgE signals degranulation of the mast cells
  6. Histamines is released into the area
  7. Histamine increases the permeability of blood capillaries and get swelling and redness in the eyes
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17
Q

What do you use in management of allergic rhinoconjunctivitis/

A

antihistamines, mast cell stabilizers, NSAIDS

also avoid the antigen in general

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18
Q

Why should steroids be avoided in allergic rhinoconjunctivitis?

A

they are effective in treating teh allergic rhinoconjuncitbitis itself, but cause complications like glaucoma, cataracts and secondary infection so it’s not worth it

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19
Q

What is the most common virus leading to conjunctivitis in neonates? In the rest of the population?

A

neonates - HSV1

rest of the population = adenovirus

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20
Q

Besides HSV1 and adenovirus, what are some other viruses that can cause viral conjunctivitis?

A

coxsackie A24, HSV 2, VZV, EBV, rubella, mumps, influenza

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21
Q

What typically precedes a viral conjunctivitis?

A

an upper respiratory infection

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22
Q

Where will you particularly see lymphadenopathy in viral conjunctivitis?

A

preauricular adenopathy

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23
Q

How do you treat viral conjunctivitis?

A

it’s usually benign and self limited

treat with cold and warm compress and maybe topical vasoconstrictors

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24
Q

What sort of virus is the adenovirus?

A

it’s a non-enveloped, dsDNA virus

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25
Q

Where does adenovirus cause lytic infection and where does it cause latent infection?

A

lytic in epithelial cells and latent in lymphoid cells

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26
Q

WHy do some strains of adenoviruses infect the respiratory tract, while some do conjunctive and others do enteri corgans?

A

the differnt strains ahve different membrane fibers that will attach to different receptors found on different cells thoruhout the body

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27
Q

What 2 adenovirus strains very commonly cause conjunctivitis?

A

19 and 37

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28
Q

What new test is available to detect adenovirus hexon protein in eye swabs?

A

adenoplus - you dab and drag is across the lower lid

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29
Q

What is the most common bacteria causing acute bacterial conjunctivitis?

A

staph aureus

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30
Q

What are some other bacteria that can cause conjunctibitsi?

A

streptococcus pneumoniae, haemophilus influenze (kids), moraxella, e. coli, pseudomonas aeruginosa

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31
Q

If bacterial conjunctivitis is typically self limiting, why do we treat it with antibiotics?

A

treating decreases patient morbiditiy and transmission

32
Q

What is the typical antibiotic used for conjunctivitis?

A

moxifloxacin solution - it’s the vest cover for both gram positive and gram negatives in this situation

33
Q

Since moxifloxacin solution is expensive, what oother drug combo is usually given?

A

trimethoprim and polymyxin B

34
Q

Moxifloxacin is a fluoroquinolone - wha tis the mechanism of action?

A

it binds DNA gyrase and disrupt DNA synthesis

35
Q

What is the mechanism of action for trimethoprim?

A

it’s blocks DHFR so you don’t have the folate pathway for making nucleotides

36
Q

What is the mechanism of action for polymyxin B?

A

It will punch holes in the membranes of gram negative organisms

37
Q

True or false, you typically do cultures of conjunctivitis to determine the species.

A

false - usually not necessary - treat epirically wtih broad coverage

only get cultures for recurrent infections, severe infections or no response to treatment

38
Q

What bacterial causes HYPERACUTE bacterial conjunctibitis

A

Neisseria gonorrhoaea

(sometimes meninigtidis, but much less often)

39
Q

What symptoms will you see with a hyperacute bacterial conjunctibitis?

A

copiois yellow-green discharge - purulent

preauricular adenopathy (even though this is usually with the viral conjunctiitis)

40
Q

How do you do a gram stain if you’re concerned about hyperacute bacterial conjunctivitis?

A

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

41
Q

How do you treat hyperacute bacterial conjunctivitis? Why does it need to be quick?

A

systemic ceftriazone

it can quickly progress to corneal ulceration and perforation

42
Q

What is ophthalmia neonatorum?

A

it’s conjuctibitis or keratoconjunctibitis occurring within the first month of life

43
Q

What do we do in the US to try to circumvent ophthalmia neonatorum?

A

we do prophylactic erythromycin ointment in newborn eyes

44
Q

What type of drug is erythrromycin? How does it work?

A

it’s a macrolide

it inhibits translation by binding the 23S rRNA of the 50S ribosomal subunit

45
Q

What is the spectrum for erythromycin?

A

broa coverage of respiratory pathogens and chlamydia

46
Q

Resistance to erythromycin is becoming an issue - what are the mechanisms for resistance?

A

increased efflux

hydrolysis of drug by esterases

methylation of the drug’s binding site

47
Q

What are the adverse effects of the macrolides like erythromycin?

A

GI discomfort

hepatic failure

prolonged QT interval

inhibits cyt p450, so check other meds

48
Q

What bacterial is associated with the leading cuase of blindness worldwide?

A

chlamydia trachomatis - because you don’t get lasting immunity, recurrent infection is common, resulting in repeat damage to blindness

49
Q

How do you diagnose chlamydia trachomatis conjunctibitis?

A

direct fluorescent antibody testing

50
Q

What is the treatment for chlamydia trachomatis conjunctiitis? What other organism should you be owrried about?

A

azithromycin

be worries about coinfection with N gonorrhoae

51
Q

Describe the life cycle of chlamydia trachomatis.

A
  1. elementary body enters epithelial cells
  2. converts to reticular body form in the cell
  3. replicates with binary fission
  4. reverts back to elementary body form
  5. elementary body leaves cell to infect neighbors
52
Q

What is the isue with interferon-gamma and chlamydia trachomatis?

A

it can create persistent form of the infeciton which is reactivated when the antibiotic is removed

53
Q

Which form of the chlamydia trachomatis - elementary or reticulate–will have a rigid otuer membrane?

A

elementary - it has to be able to survive in the environment

54
Q

What are the two basic forms of blepharitis?

A

stye = localized inflammation in eyelash follicle

chalazion = a lipogranuloma plug of a meibomian gland

55
Q

What is the treatment for blepharitis?

A

warm compress/massage to open gland

erythromycin ointment for bacterial

56
Q

What sort of worrisome infection is herpes simplex 1 associated with?

A

keratoconjunctibitis

57
Q

Although HSV1 conjunctivitis presents similar to adenovirus at first, what is the distinguishing feature/

A

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

58
Q

Why should you avoid corticosteroids in treating HSV1 keratoconjunctiitis?

A

it’s more likely to lead to corneal penetration

59
Q

If there is corneal involvement of an HSV conjuncivitis, how should you treat it?

A

topical trifluridine and systemic acyclovir

60
Q

BOth acyclovir and trifuridine are prodrugs that will act as chain terminators. Why is trifuridine more toxic and therefore only used topically?

A

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

61
Q

What are some symptoms besides eye redness you would have with keratitis?

A

vision defects

photophobia

pain (cornea has lots of nerve endings)

foreign body sensation

62
Q

What viruses are most commonly associated with keratitis?

A

HSV1 is the ost common

then adenovirus and VZV

63
Q

What bacteria are most commonly causing bacterial keratitis?

A

staph auerus

staph epidermidis

pseudomonas aeruginosa

baccilus cereus

64
Q

What ameba can cause keratitis?

A

acanthamoeba - often resides in improperly stores contact lens cleaning fluids

65
Q

What is the treatment for viral keratitis? bacterial?

A

viral = trifluridine and acyclovir

bacteria: moxifloxacin eye drops

66
Q

Who is at the highest risk for pseudomonas aeruginosa eye infections?

A

contact lens wearers

67
Q

Why is pseudomonas aeroginosa naturally resistant to many antibiotics?

A

it can form biofilms

68
Q

What virulence factor can pseudomonas produce to inhibit mitochondrial enzymes and disrupt ciliary beating in keratitis?

A

a blue pigment called pyocyanin

69
Q

What virulence factors will break down the corneal epithelium in pseudomonas keratitis?

A

elastase and alkaline protease

70
Q

What are the two types of uveitis?

A

iritis - anterior uveitis

chorioretinitis - posterior uveitis

71
Q

How are the symptoms for iritis and chorioretinitis different?

A

iritis - photophobia, pain, decreased acuity

chorioretinitis - floaters, no pain (more common)

72
Q

Why is chorioretinitis frequency a manifestation of systemic disease?

A

It’s affecting the retinal arteries and it’s usually blood borne to that area from somewhere else in the body

73
Q

What two congenital infections common cause chorioretinitis in neonates?

A

toxoplasma

CMV

74
Q

What are two worm parasitic infections that can cause eye infections - chorioretinitis in particular?

A

toxocara cani

onchocerca volvulus (river blindness from sand flies)

75
Q

Who typically gets endophthalmitis - it’s rare.

A

people who have had recent intraocular surgery like cataract surgery.

the agent is from normal flora like pseudomonas, staph, or candida

76
Q

How do you treat endophthalmitis?

A

you inject fluoroquinoloe or vancomycin into the eye

77
Q
A

Neuro Block 3 (24 decks)

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