Microbiology in Opthamology

Question 1

what are the 3 causes of bacterial conjunctivitis in neonates?

Answer 1

staph aureus
Neisseria gonorrhoea
chlamydia trachomatis
all cases in neonates must be referred to ophthalmology

Question 2

3 causes of bacterial conjunctivitis in other ages?

Answer 2

staph aureus
strep pneumoniae
haemophilus influenzae (esp in children)

Question 3

how is bacteria conjunctivitis managed?

Answer 3

swab
topical antibiotic (usually chloramphenicol)
drops vs ointment

Question 4

when must chloramphenicol be avoided?

Answer 4

if history of aplastic anaemia or allergy

be aware that allergy may be present if symptoms worsen

Question 5

3 causes of viral conjunctivitis?

Answer 5

adenovirus
herpes simplex
herpes zoster

Question 6

what may indicate a chlamydial conjunctivitis?

Answer 6

chronic history
unresponsive to treatments
suspect in bilateral conjunctivitis in young adults
may or may not have symptoms of urethritis or vaginitis
need contact tracing

Question 7

what may chlamydial conjunctivitis look like?

Answer 7

follicles like tiny grains of rice in the conjunctiva

can cause tubtarsal scarring

Question 8

3 causes of microbial keratitis?

Answer 8

bacteria
viruses
fungi

Question 9

what does bacterial keratitis look like?

Answer 9

level of white within the cornea due to mixing up of precisely arranged collagen fibres as a result of swelling, inflammation etc

Question 10

what is a hypopyon?

Answer 10

a leukocytic exudate, seen in the anterior chamber, usually accompanied by redness of the conjunctiva and the underlying episclera

Question 11

how is bacterial keratitis managed?

Answer 11

need admission for hourly drops
daily review
usually in association with other corneal pathology or contact lens wearer

Question 12

name 2 causes of viral keratitis?

Answer 12

herpes

adenovirus

Question 13

bacterial vs viral keratitis?

Answer 13

bacterial = usually have an underlying pathology associated
viral = can just happen in otherwise healthy eyes

Question 14

how might herpetic keratitis present?

Answer 14

dendritic ulcer
shows under blue light
incredibly painful (especially the first time)
can be recurrent which can eventually result in reduced corneal sensation

Question 15

how is herpetic keratitis managed?

Answer 15

NEVER GIVE STEROIDS
- can cause a corneal melt and perforation
??? (flurosine?)

Question 16

how might adenoviral keratitis present?

Answer 16

subepithelial infiltrates
bilateral
usually after URTI
may affect vision
contagious

Question 17

how is adenoviral keratitis managed?

Answer 17

can give topical AB to prevent secondary infection

can require steroids to speed up recovery if it becomes chronic

Question 18

what is acanthamoeba?

Answer 18

type of fungal keratitis
- pseudomonas aeruginosa
usually occurs in contact lens wearer
more indolent course than microbial keratitis
ususally a history of trauma from vegetation (e.g gardener)
takes a long time to heal

Question 19

what are the features of orbital cellulitis?

Answer 19

painful (esp. on eye movements)
proptosis
associated with paranasal sinusitis
pyrexial
sight threatening
swollen, red, puffy area around the eye

Question 20

how is orbital cellulitis managed?

Answer 20

cared for by ENT and ophthalmology
CT scan to identify orbital abscesses if any suggestion of a restriction of muscles or optic nerve dysfunction (ask about red colour vision, follow finger etc)
broad spectrum AB and close monitoring
abscesses will require drainage

Question 21

what can cause orbital cellulitis?

Answer 21

direct extension from sinus
extension from focal orbital infection
post-operative

Question 22

what organisms can cause orbital cellulitis?

Answer 22

staph
strep
coliforms
haemophilus influenzae
anaerobes

Question 23

what is endophthalmitis?

Answer 23

devastating infection inside of the eye

Question 24

what can cause endophthalmitis?

Answer 24

post surgical (most common - leads to sudden blindness)
endogenous (spread from systemic infection in other areas of the body like endocarditis)

Question 25

how does endophthalmitis present?

Answer 25

very painful decreasing vision very red eye sight threatening

Question 26

what organisms usually cause endophthlamitis?

Answer 26

often conjunctival commensals | most common = staph epidermidis

Question 27

how is endophthalmos managed?

Answer 27

``` intravitreal - amikacin - ceftazidime - vancomycin - topical antibiotics systemic antibiotics ```

Question 28

3 causes of chorioretinitis?

Answer 28

CMV in AIDS Toxoplasma gondii Toxocara canis (worms)

Question 29

what does CMV chorioretinitis look like?

Answer 29

many areas of exudate and haemorrhages in the retina

Question 30

where is toxoplasma gondii likely to come from?

Answer 30

cats and raw meat

Question 31

how does toxoplasmosis infection present?

Answer 31

mild flu like illness can enter latent phase with cysts forming in an immunocomprimised patient rarely causes further problems in healthy people

Question 32

how is toxoplasmosis managed?

Answer 32

can be left alone requires systemic treatment is sight threatening can reactivate

Question 33

what is toxocara?

Answer 33

``` parasitic nematode (roundworm) affects cats and dogs, unable to replicate in humans but remains an immature form of the worm ```

Question 34

what do toxocara do in the body?

Answer 34

often self limiting as they cannot replicate | form granulomas which can cause irreversible visual loss

Question 35

how are bacterial, chlamydial and viral eye infections diagnosed?

Answer 35

swabs for culture

Question 36

how is bacterial keratitis diagnosed?

Answer 36

corneal scrapes

Question 37

how is endophthalmitis diagnosed?

Answer 37

aqueous/vitreous for culture

Question 38

how is acanthamoeba diagnosed?

Answer 38

microscopy/culture

Question 39

how is toxoplasma and toxocara diagnosed?

Answer 39

serology

Question 40

what are the 3 broad categories of antibiotics?

Answer 40

inhibit protein synthesis inhibit cell wall synthesis inhibit nucleic acid synthesis

Question 41

what is the most commonly used topical antibiotic and what does it do?

Answer 41

chloramphenicol inhibits peptidyl transferase enzyme which stops bacterial protein being made bacteriocidal for strep and haemophilus bacteriostatic for staph

Question 42

how can chloramphenicol be delivered and what are 3 possible side effects?

Answer 42

``` ointment or dops must be kept in the fridge side effects: - allergy - irreversible aplastic anaemia (rare) - grey baby syndrome (if too much given?) ```

Question 43

name 2 types of antibiotics which inhibit cell wall synthesis and how they work

Answer 43

penicillins and cephlasporins both have a common B lactam ring B lactam ring inhibits enzyme which makes bacterial cell wall without cell wall, bacteria die

Question 44

name an antibiotic which inhibits nucleic acid synthesis can how

Answer 44

quinolones (e.g ofloxacin) inhibits DNA gyrase (an enzyme which compresses bacterial DNA into supercoils) inhibition of DNA gyrase leads to unwinding of supercoils and cell death

Question 45

name 3 common treatments for bacterial conjunctivitis

Answer 45

chloramphenicol = treats most apart from pseudomonas fusidic acid = treats staph aureus gentamicin = treats gram -ves - e.g coliforms, pseudomonas)

Question 46

name a commonly used antiviral and how it works

Answer 46

``` acyclovir inhibits viral DNA synthesis base analogue (mimics guanine) topical and systemic used for dendritis ulcers of the cornea ```

Question 47

how is chlamydial conjunctivitis managed?

Answer 47

topical oxytetracycline | - adults may also need oral azithromycin for genital chlamydia infection

Question 48

name 2 treatments for bacterial keratitis

Answer 48

a 4-quinolone (ofloxacin) = treats most gram -ves but not strep pneumonia gentamicin and cefuroxime = treats most gram +ve and -ves)