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Ophthalmology > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is infection of the cornea known as?

A

Keratitis

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2
Q

What is infection of the entire globe of the eye known as?

A

Endophthalmitis

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3
Q

What organisms commonly cause bacterial conjunctivitis in neonates?

A

Staph aureus, Neisseria gonorrhoeae, chlamydia trachomatis (all need referral to ophthalmology)

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4
Q

What are some causes of bacterial conjunctivitis in other age groups?

A

Staph aureus, strep pneumoniae, haemophilus influenzae (especially in children)

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5
Q

What is the treatment for bacterial conjunctivitis?

A

Swab then topical antibiotic = usually chloramphenicol qds

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6
Q

When should chloramphenicol be avoided?

A

If history of aplastic anaemia or allergic reaction to drug

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7
Q

What are some causes of viral conjunctivitis?

A

Adenovirus, herpes simplex, herpes zoster

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8
Q

When should chlamydial conjunctivitis be suspected?

A

Chronic history = unresponsive to treatment

Bilateral conjunctivitis in young patient

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9
Q

What symptoms may also be present in chlamydial conjunctivitis?

A

Those of urethritis or vaginitis

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10
Q

What must be done if chlamydial conjunctivitis is diagnosed?

A

Contact tracing must be done for that patient

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11
Q

What is a potential complication of chlamydial conjunctivitis?

A

Subtarsal scarring

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12
Q

What organisms may cause the formation of hypopyon in keratitis?

A

Bacterial or fungi

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13
Q

What is hypopyon?

A

White exudate in anterior chamber with underlying redness of the conjunctiva and underlying episclera

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14
Q

What is bacterial keratitis usually associated with?

A

Other corneal pathology or contact lens wear

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15
Q

How are patients with bacterial keratitis managed?

A

Admitted to hospital and given hourly drops, reviewed daily

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16
Q

What are the main viral causes of keratitis?

A

Herpes and adenovirus

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17
Q

What are the features of herpetic keratitis?

A

May have dendritic ulcer, very painful, can be recurrent

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18
Q

What do recurrences of herpetic keratitis result in?

A

Reduced corneal sensation

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19
Q

What may occur if herpetic keratitis is treated with steroids?

A

May cause corneal melt or perforation

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20
Q

What are some features of adenovirus keratitis?

A

Show subepithelial infiltrates, bilateral, usually follows URTI, may affect vision

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21
Q

When are steroids used on adenovirus keratitis?

A

To speed up recovery if chronic

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22
Q

When are topical antibiotics used in adenovirus keratitis?

A

To prevent secondary infection

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23
Q

What fungal organisms that cause keratitis are associated with contact lenses?

A

Acanthamoeba, pseudomonas aeruginosa

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24
Q

What are the features of fungal keratitis?

A

More indolent course than microbial keratitis, usually history of trauma from vegetation, takes long time to heal

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25
Q

What are the symptoms of orbital cellulitis?

A

Painful (especially on eye movement), proptosis, often associated with paranasal sinusitis, pyrexia

26
Q

Is orbital cellulitis serious?

A

Yes = sight threatening, patient needs care from ENT and ophthalmology

27
Q

Why are CT scans done in orbital cellulitis?

A

To identify orbital abscesses

28
Q

What are some sources of orbital cellulitis?

A

Direct extension from sinus, extension from focal orbital infection (e.g infected chalazion, dacryocystitis), may be post-operative

29
Q

What must you differentiate between in orbital cellulitis?

A

Preseptal or orbital infection

30
Q

What organisms are associated with orbital cellulitis?

A

Staph, strep, coliforms, haemophilus influenzae, anaerobes

31
Q

When should you do a scan on a patient with orbital cellulitis?

A

If there is a suggestion of restrictions of muscles or optic nerve dysfunction

32
Q

How is orbital cellulitis treated?

A

Broad spectrum antibiotic and monitor closely, sometimes abscesses need drained

33
Q

What is endophthalmitis?

A

Devastating infection of inside of eye = may be post-surgical or endogenous, sight threatening

34
Q

What are some symptoms of endophthalmitis?

A

Very painful, decreased vision, very red eye

35
Q

What organisms cause endophthalmitis?

A

Often conjunctival commensals = usually staph epidermidis

36
Q

What is the treatment for endophthalmitis?

A

Intravitreal amikacin/ceftazidime/vancomycin and topical antibiotics

37
Q

What are some common causes of chorioretinitis?

A

CMV in AIDS patients, toxoplasma gondii, toxocara canis

38
Q

What is a feature of chorioretinitis caused by CMV in AIDS patients?

A

Usually haemorrhagic

39
Q

What is toxoplasma gondii?

A

Protozoan infection = usually from cats or raw meat, usually causes mild flu like illness that causes no further problems

40
Q

How does toxoplasma gondii act in immunocompetent patients?

A

Enters latent phase with cyst forming

Can reactivate and needs systemic treatment if sight threatening

41
Q

What is toxocara canis?

A

Parasitic nematode (roundworm) that normally affects cats and dogs

42
Q

Why is toxocara canis infection self-limiting?

A

Organism unable to replicate in humans = remains in immature form (larvae)

43
Q

How may toxocara infection affect sight?

A

Can form granulomas which may threaten sight

44
Q

What organisms is swabbing for culture suitable for?

A

Bacterial, viral, chlamydial

45
Q

How is bacterial keratitis diagnosed?

A

Corneal scrapes

46
Q

How is endophthalmitis diagnosed?

A

Aqueous/vitreous sample for culture

47
Q

How is acanthamoeba diagnosed?

A

Microscopy and culture

48
Q

How are toxoplasma and toxocara diagnosed?

A

Serology

49
Q

What is chloramphenicol?

A

Most commonly used topical antibiotic = ointment or drops

50
Q

How does chloramphenicol work?

A

Inhibits peptidyl transferase = stops bacterial protein being made

51
Q

What are some organisms that chloramphenicol is active against?

A 
Bactericidal = strep, haemophilus influenzae
Bacteriostatic = staph
52
Q

What are some side effects of chloramphenicol?

A

Allergy, irreversible aplastic anaemia, grey baby syndrome

53
Q

What are some antibiotics that inhibit bacterial cell wall synthesis?

A

Penicillin and cephalosporins = have common beta lactam ring

54
Q

What does a beta lactam ring do to bacteria?

A

Inhibits the enzyme that makes the bacterial cell wall

55
Q

What is an antibiotic class that inhibits nucleic acid synthesis?

A

Quinolones = inhibit DNA gyrase (enzyme that compresses bacterial DNA into supercoils), inhibition of DNA gyrase leads to unwinding of supercoils

56
Q

What is a common contaminate of eye drop bottles?

A

Pseudomonas = bottles must be kept contaminate free for four weeks (get new drops after 28 days)

57
Q

What are some antibiotics used to treat bacterial conjunctivitis?

A

Chloramphenicol = treats most (except p.aeruginosa)
Fusdic acid = treats staph aureus
Gentamicin = treats most gram negatives

58
Q

How does aciclovir work?

A

Inhibits viral DNA synthesis

59
Q

What are some features of aciclovir?

A

Base analogue (mimics guanine), topical and systemic, used for dendritic ulcers of cornea

60
Q

How is chlamydial conjunctivitis treated?

A

Topical oxytetracycline = adults may also need azithromycin for genital chlamydial infection

61
Q

What are some antibiotics used to treat bacterial keratitis?

A

4-quinolone (ofloxacin) = treats most gram negative but not active against strep. pneumoniae
Gentamicin + cefuroxime = combo will treat most gram negatives and positive organisms

62
Q

What is the distinguishing feature of chlamydial conjunctivitis?

A

It causes follicles

Ophthalmology (20 decks)

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