Microbiology

Question 1

What is infection of the cornea known as?

Answer 1

Keratitis

Question 2

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

Answer 2

Endophthalmitis

Question 3

What organisms commonly cause bacterial conjunctivitis in neonates?

Answer 3

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

Question 4

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

Answer 4

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

Question 5

What is the treatment for bacterial conjunctivitis?

Answer 5

Swab then topical antibiotic = usually chloramphenicol qds

Question 6

When should chloramphenicol be avoided?

Answer 6

If history of aplastic anaemia or allergic reaction to drug

Question 7

What are some causes of viral conjunctivitis?

Answer 7

Adenovirus, herpes simplex, herpes zoster

Question 8

When should chlamydial conjunctivitis be suspected?

Answer 8

Chronic history = unresponsive to treatment

Bilateral conjunctivitis in young patient

Question 9

What symptoms may also be present in chlamydial conjunctivitis?

Answer 9

Those of urethritis or vaginitis

Question 10

What must be done if chlamydial conjunctivitis is diagnosed?

Answer 10

Contact tracing must be done for that patient

Question 11

What is a potential complication of chlamydial conjunctivitis?

Answer 11

Subtarsal scarring

Question 12

What organisms may cause the formation of hypopyon in keratitis?

Answer 12

Bacterial or fungi

Question 13

What is hypopyon?

Answer 13

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

Question 14

What is bacterial keratitis usually associated with?

Answer 14

Other corneal pathology or contact lens wear

Question 15

How are patients with bacterial keratitis managed?

Answer 15

Admitted to hospital and given hourly drops, reviewed daily

Question 16

What are the main viral causes of keratitis?

Answer 16

Herpes and adenovirus

Question 17

What are the features of herpetic keratitis?

Answer 17

May have dendritic ulcer, very painful, can be recurrent

Question 18

What do recurrences of herpetic keratitis result in?

Answer 18

Reduced corneal sensation

Question 19

What may occur if herpetic keratitis is treated with steroids?

Answer 19

May cause corneal melt or perforation

Question 20

What are some features of adenovirus keratitis?

Answer 20

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

Question 21

When are steroids used on adenovirus keratitis?

Answer 21

To speed up recovery if chronic

Question 22

When are topical antibiotics used in adenovirus keratitis?

Answer 22

To prevent secondary infection

Question 23

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

Answer 23

Acanthamoeba, pseudomonas aeruginosa

Question 24

What are the features of fungal keratitis?

Answer 24

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

Question 25

What are the symptoms of orbital cellulitis?

Answer 25

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

Question 26

Is orbital cellulitis serious?

Answer 26

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

Question 27

Why are CT scans done in orbital cellulitis?

Answer 27

To identify orbital abscesses

Question 28

What are some sources of orbital cellulitis?

Answer 28

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

Question 29

What must you differentiate between in orbital cellulitis?

Answer 29

Preseptal or orbital infection

Question 30

What organisms are associated with orbital cellulitis?

Answer 30

Staph, strep, coliforms, haemophilus influenzae, anaerobes

Question 31

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

Answer 31

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

Question 32

How is orbital cellulitis treated?

Answer 32

Broad spectrum antibiotic and monitor closely, sometimes abscesses need drained

Question 33

What is endophthalmitis?

Answer 33

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

Question 34

What are some symptoms of endophthalmitis?

Answer 34

Very painful, decreased vision, very red eye

Question 35

What organisms cause endophthalmitis?

Answer 35

Often conjunctival commensals = usually staph epidermidis

Question 36

What is the treatment for endophthalmitis?

Answer 36

Intravitreal amikacin/ceftazidime/vancomycin and topical antibiotics

Question 37

What are some common causes of chorioretinitis?

Answer 37

CMV in AIDS patients, toxoplasma gondii, toxocara canis

Question 38

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

Answer 38

Usually haemorrhagic

Question 39

What is toxoplasma gondii?

Answer 39

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

Question 40

How does toxoplasma gondii act in immunocompetent patients?

Answer 40

Enters latent phase with cyst forming | Can reactivate and needs systemic treatment if sight threatening

Question 41

What is toxocara canis?

Answer 41

Parasitic nematode (roundworm) that normally affects cats and dogs

Question 42

Why is toxocara canis infection self-limiting?

Answer 42

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

Question 43

How may toxocara infection affect sight?

Answer 43

Can form granulomas which may threaten sight

Question 44

What organisms is swabbing for culture suitable for?

Answer 44

Bacterial, viral, chlamydial

Question 45

How is bacterial keratitis diagnosed?

Answer 45

Corneal scrapes

Question 46

How is endophthalmitis diagnosed?

Answer 46

Aqueous/vitreous sample for culture

Question 47

How is acanthamoeba diagnosed?

Answer 47

Microscopy and culture

Question 48

How are toxoplasma and toxocara diagnosed?

Answer 48

Serology

Question 49

What is chloramphenicol?

Answer 49

Most commonly used topical antibiotic = ointment or drops

Question 50

How does chloramphenicol work?

Answer 50

Inhibits peptidyl transferase = stops bacterial protein being made

Question 51

What are some organisms that chloramphenicol is active against?

Answer 51

``` Bactericidal = strep, haemophilus influenzae Bacteriostatic = staph ```

Question 52

What are some side effects of chloramphenicol?

Answer 52

Allergy, irreversible aplastic anaemia, grey baby syndrome

Question 53

What are some antibiotics that inhibit bacterial cell wall synthesis?

Answer 53

Penicillin and cephalosporins = have common beta lactam ring

Question 54

What does a beta lactam ring do to bacteria?

Answer 54

Inhibits the enzyme that makes the bacterial cell wall

Question 55

What is an antibiotic class that inhibits nucleic acid synthesis?

Answer 55

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

Question 56

What is a common contaminate of eye drop bottles?

Answer 56

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

Question 57

What are some antibiotics used to treat bacterial conjunctivitis?

Answer 57

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

Question 58

How does aciclovir work?

Answer 58

Inhibits viral DNA synthesis

Question 59

What are some features of aciclovir?

Answer 59

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

Question 60

How is chlamydial conjunctivitis treated?

Answer 60

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

Question 61

What are some antibiotics used to treat bacterial keratitis?

Answer 61

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

Question 62

What is the distinguishing feature of chlamydial conjunctivitis?

Answer 62

It causes follicles