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OV3017 Eye Disease > 8 - Pathogenesis of Infectious eye disease > Flashcards

8 - Pathogenesis of Infectious eye disease Flashcards

(45 cards)

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1
Q

the ocular surface is normally well protected from pathgens because it has self defense mechanisms such as

A
  1. antimicrobial properties of tears
  2. sheddng of cells on ocular surface which reduces contact with pathogens
  3. effective illumnological methods
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2
Q

what are the risk factors that pre dispose eye to infection

A
  1. immune status
  2. ocular morbidity
  3. CL wear
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3
Q

what are the causes of infection

A

pathogens such as:
bactera, HSV, CMB, VZV

less common ones:
fungi and protozea e.g. acanthomeaba and toxoplasma

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4
Q

what is normal conjunctival flora

A

microbiial flora, present on lids and in conjunctival sac from birth + present throughout life (commensal)

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5
Q

what are commensals

A

inate defence system of eye: compete with pathogens for essential nutrients

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6
Q

what bacteria are normal conjunctival flora

A

gram positive

  • gram +ve cocci
    staphylococcus epidermis
    staphylococcus aureus
    micrococcuus sp
  • gram +ve baccili
    corynebacterium species
  • anaerobic
    -propinibacterium
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7
Q

external hordoleum (stye)

A
  • infection of ciliary sebaceous glands (Zeiss)
  • base of eyelashes
  • typically steph. aureus
  • typical treatment is warm compress
  • topical antibiotics needd
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8
Q

blepharitis

A
  • non infective
  • chronic or remitting

staph. aureus
staph. epidermis

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9
Q

what are the charecteristics of - staphylococci

A
  • commensals of human skin
  • gram positive
  • grow on most media
  • toxin mediated

can cause ocular surface infection e.g. conjunctivitis. if they penetrate deeper then potentially more severe infections
- common cause of food poisoning + cause damage by production of toxins

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10
Q

difference between orbital cellulitis and pre-septal cellulitis

A
  • orbital cellulitis is rare but life threatening , common in children.
  • rises from abcess in sinuses
  • proptosis
  • lid oedema
  • RAPD
  • limitation and pain on eye movements
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11
Q

where does the infection lie in preseptal cellulitis

A

in front of natural barrier

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12
Q

where does the infection lie in orbital cellulitis

A

in the orbit, behind the septum. it can spread into the cranial cavity

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13
Q

aetiology of pre-septal cellulitis / orbital infection

A
  • sinusitis
  • strep. pnemoniae / H influenzae
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14
Q

treatment for pre septal

A

antibiotics

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15
Q

treatment for pre-septal

A

antibioticst

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16
Q

treatment for orbital

A
  • antibiotics +/- surgery
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17
Q

characteristics of streptococci

A
  • commensals of mouth +gut
  • gram positive cocci - chains
  • grow on blood sugar (haemolysis)
  • mostly non pathogenic
  • can cause conjunctivitis & even deeper orbital infections
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18
Q

streptococci- spectrum of disease

A

wide (pneumonia, wound and skin infections, sepsis)

  • local infection may lead to systemic infection
  • toxin mediated
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19
Q

characteristics of haemophillus spp

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A
  • commensal of upper respiratory tract
  • gram negative rod
  • fastidious
20
Q

spectrum of disease for haemophilus spp.

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A
  • local infection / meningitis
  • much less since Hib vaccination
21
Q

conjuncitvitis presentation

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A
  • viral
  • bacterial
  • chlamydial
22
Q

bacterial conjunctivitis - charcteristics

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A
  • rapid onset
  • unilateral to bilateral in 1-2 days
  • staphylococci/streptococci/ H. influenzae

self limiting

23
Q

viral conjunctivitis characteristics

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A
  • enlargement of pre-auricular nodes
  • most common
  • unilateral > bilateral in 1 week
24
Q

viral conjunctivitis - adenovirus

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A

pharyngoconjunctival fever
- most commmon
- associated w respiratory tract infection
- resolves in 2 weeks

epidemic keratoconjunctivitis
- more severe
- lasts 1-3 weeks
- associated w subconjunctival hameorrages
- may get corneal involvement

25
what is adenovrius
- a DNA virus - 49 serotypes spread if contact with secretions e.g coughing/sneezing - formites (inanimate objects)
26
what are the 2 forms of chlamydial conjuncitvitis
- trachoma - acute inclusion conjunctivitis
27
what is trachoma
- potentially blinding condition due to exposure of ocular tissue - overcrowding + poor sanitation - follicular conjunctivitis
28
what is acute inclusion conjunctivitis
- chronic follicular conjunctivitis - usually sexually transmitted - unilateral red eye - adults - misdiagnosed - involves cornea - may be punctate keratitis with sub epithelial infiltrates
29
charactreristics of chlamydiae
- obligate intracellular parasite - life cycle resembles viruses - depend on host cell - inert infectious particles - culture not routine
30
diagnosis of chlamydiae
- serology - histology (conjunctival scrape)` - PCR (presence of chlamydial nucleic acid)
31
conunctival scrape
- using a kamura spatula - useful for chlamydia - sample taken from upper and lower sac
32
how to have an indication of the most effective antibiotic treatment for an infection?
measure the zone of inhibition of bacterial growth
33
microbial keratitis - bacteria
- bacterial keratitis most common cause of MK
34
most common bacterial corneal pathogens
- pseudomonas sp (gram -) - staphylococcous sp ( gram +) - streptococcus sp (gram +)
35
where is gram - and gram + most common
-ve in CL associated keratitis +ve in non CL wearers
36
risk factors of microbial keratitis: bacteria
- cl wear - immunosuppression - ocular surface disease - trauma
37
herpetic keratitis
- herpes simplex virus (HSV) mostly HSV1 as 2 causes genital herpes - varicella zoster virus (VSV) ophthalmic shingles
38
mechanisms of bacterial pathogenictiy
- some bacteria produce damage through the colonisation of body surface + release toxins and only invade tissue to limited extent - some bacteria cause damage by invasion and multiplication in the tissues
39
non - infectious keratitis
- corneal response to bacterial toxins 1. CLARE 2. marginal keratitis 3. CLPU
40
marginal keratitis
- inflammatory response to bacerial toxins on lid - non infective - managed with combinations of topical steroid and antibiotics + lid hygiene
41
uveitis
- most cases non infective and idiopathic
42
infectious analogies of anterior uveitis
- HSV - VSV
43
Infectious aetiologies of posterior uveitis
- toxoplasosis - toxocara -syphillis CMV
44
endophthalmitis characteristics
- usually bacterial and acute - most cases exogenous e.g surgery trauma
45
classification of endopthalmitis
- acute post cataract - chronic pseudophakic - bleb related - post traumatic

OV3017 Eye Disease (19 decks)

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