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Therapeutics > pathogenesis of infectious disease > Flashcards

pathogenesis of infectious disease Flashcards

1
Q

list 4 possible ocular diseases/infections from ascending order of severity that can be caused by pathogens

A
  • periocular and orbital
  • keratitis
  • uveitis
  • endophthalmitis
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2
Q

what can the exposed condition of the ocular service implicate about disease and how does this not happen as often as thought

A

the exposed condition of the ocular surface means it is frequently in contact with disease causing micro-organisms, however the ocular surface has many defence mechanisms to ensure that it remains disease free including:

  • anti-microbial properties of the tears
  • constant shedding of the cells from the ocular surface

these reduce contact time with the pathogen and a number of affective immunological mechanisms

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3
Q

name 3 risk factors that can predispose the eye to infections

A
  • patients immune status
  • ocular morbidity
  • contact lens wear
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4
Q

list 5 potential pathogens that can cause infection of the cornea

A
  • bateria
  • HSV
  • VZV
  • protozoa
  • fungi
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5
Q

list 4 potential pathogens that can cause infection of the uvea

A
  • bacteria
  • CMV
  • VZV
  • protozoa
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6
Q

list 2 potential pathogens that can cause endophthalmitis

A
  • bacteria

- fungi

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7
Q

which potential pathogen can cause infection of the orbit

A

bacteria

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8
Q

list 5 potential pathogens that can cause infection of the lids and conjunctiva

A
  • bacteria
  • chlamydia
  • adenovirus
  • HSV
  • VZV
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9
Q

what are the 2 least common pathogens to affect the eye

A

fungi and protozoa

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10
Q

where in the eye are microbial flora usually present and since when

A
  • on the eyelids and in the conjunctiva sac

- from birth and are present throughout the life

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11
Q

what are these harmless microbial flora called

A

commensals

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12
Q

what type of non-pathogenic microbes make up the microbial flora and which microbes less commonly make up the microbial flora

A
  • most commonly gram +ve bacteria

- less commonly environmental fungi and viruses

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13
Q

which parts of the eye are there no microbes/commensals at all

A
  • cornea
    and
  • anterior chamber

are sterile

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14
Q

what do the commensals found on the eyelid and conjunctiva form

A

part of the innate defence system of the eye, they compete with potential pathogens for essential nutrients

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15
Q

what 3 classes of bacteria make up the normal conjunctival and eyelid flora

A
  • gram +ve cocci (sphere shape)
  • gram +ve bacilli (rod shaped)
  • anaerobic
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16
Q

list the 3 types of gram +ve cocci commensal bacteria

A
  • staphylococcus epidermis 30-80%
  • staphylococcus aureus 3-25%
  • micrococcus sp. 1-28%
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17
Q

which bacterial commensal accounts for 30-80% of the conjunctiva and lids

A

gram +ve staphylococcus epidermis

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18
Q

which bacterial commensal accounts for 3-25% of the conjunctiva and lids

A

gram +ve staphylococcus aureus

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19
Q

which bacterial commensal accounts for 1-28% of the conjunctiva and lids

A

gram +ve micrococcus

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20
Q

what is the name of the gram +ve bacilli commensal bacteria found on the conjunctiva and lids

A

corynebacterium species 5-83%

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21
Q

which gram +ve bacterial commensal accounts for 5-38% of the conjunctiva and lids

A

grame +ve bacilli corynebacterium species

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22
Q

what is the name of the anaerobic commensal bacteria found on the conjunctiva and lids

A

propionibacterium sp. 0-33%

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23
Q

which bacterial commensal accounts for 0-33% of the conjunctiva and lids

A

propionibacterium (anaerobic)

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24
Q

when can all the commensal bacteria found on the conjunctiva and eyelids cause disease

A

in particular circumstances when they are found in high concentration

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25
Q

list three peri ocular structures which can get infected

A
  • eyelids
  • conjunctiva
  • lacrimal system
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26
Q

name 2 orbital infections

A
  • orbital cellulitis

- pre septal cellulitis

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27
Q

name a peri-ocular infection of the eyelid

A

external hordoleum (stye)

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28
Q

what is a external hordoleum (stye) found on the eyelid an infection of

A
  • the ciliary sebaceous gland (zeis)

- typically staph. aureus

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29
Q

what form of treatment is needed to treat a external hordoleum (stye)

A

most commonly warm compresses

topical antibiotics if needed

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30
Q

what else has to be affected as well as the gland of zeis for the infection to be a internal hordoleum

A

meibomian glands

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31
Q

what are the signs and symptoms associated with a external hordoleum (stye)

A
  • lid swelling
  • lid tenderness
  • collection of pus under the skin
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32
Q

name a peri-ocular infection of the eyelid other than a external hordoleum (stye)

A

blepharitis - inflammation of the eyelids

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33
Q

what are the 2 forms of blepharitis

A

chronic or remitting

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34
Q

what 2 aetiologies can blepharitis have

A

infective or non-infective (often)

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35
Q

what are the 2 infectious organisms that cause blepharitis

A
  • staph, aureus

- staph epidermis

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36
Q

what is the treatments of blepharitis

A
  • eyelid hygiene alone

- may require topical antibiotics

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37
Q

what are the characteristics of the staphylococci bacteria

A
  • commensals of human skin
  • gram +ve cocci (clumps)
  • grow on most media
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38
Q

what is the spectrum of disease caused by staphylococci bacteria

A
  • can be local such as conjunctivitis or deep infection as it can penetrate into deeper tissues
  • can cause toxin mediated disease, where it produces damage primarily through the production of toxins which are cytotoxic for cells and can cause harm
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39
Q

what are the signs of pre septal cellulitis that differentiates it from orbital cellulitis

A

normal vision and no pupillary defect

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40
Q

what are the signs of orbital cellulitis that differentiates it from pre septal cellulitis

A
  • ophthalmoplegia (down and out)
  • pupillary defect/RAPD
  • proptosis
  • pain
  • painful eye movements
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41
Q

what can orbital cellulitis arise from

A

abscess in the ethmoid sinus and less commonly the maxillary and frontal, which spreads into the orbit

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42
Q

who is orbital cellulitis more commonly found in

A

children

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43
Q

where can the infection of orbital cellulitis spread to which makes it sight and life threatening

A

to the cranial cavity

as there is direct connection between the orbit and the cranium

44
Q

where does the septum run

A

from the orbital margins to the tarsal plates

45
Q

how many orbital infections does pre septal cellulitis account for

A

94% (most common)

46
Q

how many orbital infections does orbital cellulitis account for

A

6%

47
Q

what is pre septal cellulitis and orbital cellulitis both more common in and why how much

A

in children 75% in

48
Q

what are the 2 aetiologies of pre septal cellulitis

A
  • sinusitis in 80-90% of cases

- strep. pneumoniae / H.influenza

49
Q

what is used in the diagnosis of an orbital infection

A

CT scan is the most helpful in DDX

50
Q

what is the treatment for pre septal cellulitis

A

antibiotics

against potential causative organisms such as, staph aureus, strep pneumonia or H. influenza

51
Q

what is the treatment for orbital cellulitis

A

drainage of abscess and concurrent IV antibiotics

52
Q

name the 3 characteristics of the bacteria streptococci

A
  • commensals of mouth/gut
  • gram +ve cocci (chains)
  • grows on blood agar (haemolysis)
53
Q

what is the spectrum of disease of the bacteria streptococci

A
  • wide
  • local (conjunctivitis) to systemic infections (pneumonia or meningitis)
  • toxin mediated disease
54
Q

what distant appearance does the bacteria streptococci cause on an agar plate

A

they cause a clear zone called haemophilus

55
Q

what are three characteristics of haemophilus spp

A
  • commensal of URT
  • gram negative rod
  • fastidious (grows on chocolate agar = a variant of blood agar)
56
Q

haemophilus spp are ____________ pathogens who live in the ______ without causing __________ but with reduced __________ functions or ___________ inflamed tissues cause _____________ for it to cause ___________

A

haemophilus spp are opportunistic pathogens who live in the host without causing disease but with reduced immune functions or chronically inflamed tissues cause opportunity for it to cause infection

57
Q

what is the spectrum of disease of the bacteria haemophilus spp

A
  • much less since vaccination

- local infection (sinitis or conjunctivitis) to meningitis or pneumonia

58
Q

which group of patients is conjunctivitis most common in

A

children

59
Q

which 3 pathogens can present as conjunctivitis

A
  • viral
  • bacterial
  • chlamydial
60
Q

what evaluation is often not done with conjunctivitis and why

A

lab can be done but isn’t done as much because conjunctivitis is self limiting

61
Q

when will you carry out a scraping/swab of conjunctivitis on a patient and why

A

only done on ophthalmia neonatorium (if contract in 1st month of life) as they need to be referred for intensive treatment

62
Q

what type of conjunctivitis do girl and chlamydial pathogens cause

A

characteristic follicular conjunctivitis

63
Q

what are the characteristics of bacterial conjunctivitis

A
  • incidence is unknown
  • rapid onset
  • unilateral, but bilateral after 1-2 days
64
Q

name the bacteria involved acute in conjunctivitis in adults and children

A

staphylococcus aureus

65
Q

name the bacterias involved in acute conjunctivitis in children only

A
  • strep. pneumo

- H. influenza

66
Q

name the bacteria involved in chronic conjunctivitis

A
  • due to endotoxins
  • staphylococcus aureus
  • moraxella
  • enterobacteriacae
67
Q

what may be difficult with chronic conjunctivitis

A

to eradicate it

68
Q

what other conditions is viral conjunctivitis commonly associated with

A

cold and flu

69
Q

what is the most common form of conjunctivitis

A

viral

70
Q

what are the characteristics of viral conjunctivitis

A
  • acute
  • unilateral but bilateral after 1 week
  • often also get pre-auricular nodes
  • self limiting - recovery after a few days only
  • usually no sequelae
71
Q

which virus is viral conjunctivitis caused by

A

adenovirus

72
Q

what are the 2 variations of viral conjunctivitis

A
  • pharyngoconjunctival fever

- epidemic keratoconjunctivitis

73
Q

which adenovirus serotypes is pharyngoconjunctival fever variation of viral conjunctivitis caused by and what is this type characterised by

A

3, 4 and 7

characterised by pre auricular lymph node enlargement in 90% of cases

74
Q

which is the commonest type of viral conjunctivitis

A

pharyngoconjunctival fever

75
Q

after how long does the pharyngoconjunctival fever variation of viral conjunctivitis resolved

A

within 2 weeks

76
Q

which form of viral conjunctivitis is more severe

A

epidemic keratoconjunctivitis

77
Q

how long does epidemic keratoconjunctivitis type of viral conjunctivitis last

A

1-3 weeks

78
Q

what 2 things is associated with epidemic keratoconjunctivitis type of viral conjunctivitis

A
  • subconjunctival haemorrhage in 33% of cases

- may get corneal involvement - sub epithelial infiltrates in 20-30% of cases

79
Q

which adenoviral serotypes is epidemic keratoconjunctivitis type of viral conjunctivitis caused by

A

8, 11 & 19

and produces a mixed papillary and follicular conjunctival response

80
Q

what type of virus is the aden virus

A

a DNA virus

with 49 serotypes

81
Q

which 2 ways is the adenovirus spread

A
  • fomites (virus can survive in inanimate objects)

- contact with secretions e.g. following cough or sneeze

82
Q

what are the 2 forms of chlamydial conjunctivitis

A
  • trachoma

- follicular conjunctivitis

83
Q

what 2 things is trachoma due to

A
  • poor sanitation

- multiple untreated infections which is endemic in developing countries due to over crowding

84
Q

what can trachoma cause

A
  • palpebral conjunctival scarring
  • entropion
  • in some cases ectropion
  • ulceration and corneal scarring (due to result of corneal exposure)
85
Q

what is the treatment os trachoma associated with chlamydial conjunctivitis

A

antibiotics:
- tetracyclines
and
- erythromycin

86
Q

what causes acute inclusion conjunctivitis form of chlamydial conjunctivitis

A
  • chronic follicular conjunctivitis

- usually sexually transmitted

87
Q

what is the presentation of chlamydial conjunctivitis

A
  • unilateral red eye
  • usually mild/diffuse
  • may involve the cornea, producing punctate keratitis (& lesions similar to viral conjunctivitis)
88
Q

what are the characteristics of the pathogen chlamydiae

A
  • obligate intracellular parasite
  • depend on host cell
  • inert infectious particles
  • culture not routine (but can be cultured by conjunctival scrape)
89
Q

which 3 ways can you diagnose the pathogen chlamydia

A
  • serology
  • histology (inclusions)
  • PCR
90
Q

how is a conjunctival scrape carried out for detecting chlamydia

A
  • using a kamura spatula
  • sample taken from upper and lower conjunctival sac
  • sample is then placed on a slide and under a microscope to identify the characteristic inclusion bodies
91
Q

what are the varieties of culture media

A
  • chocolate (aerobic and anaerobic)
  • blood agar
  • Mc conkey agar (coliforms)
  • sabouranaud dextrose (fungi)
92
Q

which agar is used for particular gram -ve organisms e.g. E coli

A

Mc conkey agar (coliforms)

93
Q

how is antibiotic sensitivity tested

A
  • by impregnating antibiotics onto paper discs
  • placed on an agar plate
  • bacteria are not able to grow around anti-biotics to which they’re sensitive
  • by measuring their zones of inhibition around the discs will identify the most relevant antibiotic treatment for a infection
94
Q

list the 4 types of keratitis and what micro organism causes each one

A
  • bacterial - pseudomonas
  • viral - herpes simplex
  • fungal - fusiform
  • protozoal - acanthamoeba
95
Q

what is contact lenses the biggest risk for

A

bacterial and acanthamoeba keratitis

96
Q

what are the 4 classifications of uveitis

A
  • anterior
  • intermediate
  • posterior
  • panuveitis
97
Q

what are the aetiologies of uveitis

A
  • infectious

- non-infectious

98
Q

what is infected in uveitis

A

any part of the uveal tract e.g. iris, ciliary body or choroid, either individually or collectively

99
Q

what are the 2 infectious aetiologies of anterior uveitis

A
  • herpes simplex virus HSV (most common cause)

- varicella zoster virus VZV

100
Q

what are the 4 infectious aetiologies of posterior uveitis

A
  • toxoplasmosis (parasite)
  • toxocara
  • syphilis
  • cyclomagalovirus CMV
101
Q

which type of posterior uveitis does cyclomagalovirus CMV cause and which patients is this seen in

A

choroiditis and associated retinitis

seen in immunosuppressed individuals e.g. AIDS

102
Q

what are the characteristics of endophthalmitis

A
  • usually bacterial and acute

- in most cases due to exogenous bacteria that the internal structures is exposed to (due to surgery or trauma)

103
Q

what are the 4 classifications of endophthalmitis

A
  • acute post cataract
  • chronic pseudophakic
  • bleb-related
  • post traumatic
104
Q

from where in the eye can infected samples of edophthalmitis be taken from

A
  • aqueous humour

- vitreous humour

105
Q

what does the college of optometrist provide

A

its infection control guidance

106
Q

what 6 principles of infection control does the college of optometrists provide

A
  • principles of cleaning sterilisation and infection
  • hand hygiene
  • situations of greater risk
  • contact lenses and ophthalmic devices such as tonometer heads
  • contamination via contact lens solutions and medicine bottles
  • safe disposal waste

Therapeutics (19 decks)

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