week 1 microbiology Flashcards
name a gram +ive cocci
strep, staph
what is keratitis
inflammation of cornea
name a gram -ive cocci
neisseria
name a gram -ive cocci-bacilli
h.influenzae
name a gram -ive bacilli
psuedomonas
what is endophthalmitis
entire globe inflammation
infection of skin round eye
infection/inflammation of the eye skin
what can conjunctivitis be cause by
viral and bacterial
how to tell difference between bacterial and viral conjunctivitis?
bacterial = pus (lots) viral = watery
common infective organisms in bacterial conjunctivitis in newborn/baby
Staph aureus
Neisseria gonorrhoeae
Chlamydia trachomatis
(refer all cases to ophthalmology)
common infective organisms in bacterial conjunctivitis in adult
Staph aureus
Strep pneumoniae
Haemophilus influenzae (especially in children)
treatment for bacterial conjunctivitis
Swab
Topical antibiotic usually chloramphenical qds, (drops vs ointment)
if not responding then culture will give answer
what is difference between drops and ointment for chloramphenicol
drops = easy, need stored in fridge ointment = causes blurry vision
contraindications of using chloramphenicol
history of aplastic anaemia or allergy(worsening symptoms = allergy)
what are the main organisms causing viral conjunctivitis
Adenovirus
Herpes simplex
Herpes zoster
treating viral conjunctivitis
swab not usually necessary (can PCR if necessary).
sometimes antibiotics given to prevent secondary infection
herpes zoster ophthalmicus symptoms
- hutchinsons sign (nasocilary nerve), could have eye involvement.
- prolonged post-disease neuralgia
what are the 4 CN with parasympathetic function
3, 7, 9, 10
treatment for herpes zoster ophthalmicus
antivirus within 72hrs
chlamydial conjunctivits PC
young adult, bilateral chronic Hx of being unresponsive to treatments. vaginits or urethritis may be present
“rice grains” = follicles
subtarsal scarring can occur
chlamydia infections need contact tracing /phone number.
causes of keratitis
Bacteria
Viruses
Fungi
how can you differential bacterial/fungal keratitis from viral
hypopyon (sight threatening disease)
treatment for Bacterial keratitis
Need admission for hourly drops
Daily review
can perforate=bad
risk factors for bacterial keratitis
[Usually in association with other corneal pathology or contact lens wear]
what are the causative organisms of viral keratitis
herpes, adenovirus
what is a common finding with Herpetic keratitis
dendritic ulcer
PC of bacterial keratitis
painful red eye, short Hx, reduced vision
PC of herpetic keratitis
very painful to open eyes, may need local anaesthetic (topical). recurrence can occur with patient noticing reduced vision and less pain (reduced corneal sensation).
what should never be given to patient with PMHx of herpetic keratitis. why?
steroids - causes corneal melt and perforated cornea. develop geographical ulcer
what is seen in adenovirus keratitis?
superepithlial infiltrates
PC of adenoviral keratitis
Bilateral
Usually follows an URTI
Contagious
may affect vision
treatment of adenoviral keratitis
Can give topical AB to prevent secondary infection
Can require steroids to speed up recovery if becomes chronic
keratitis use by contact lenses (organisms)?
Acanthamoeba
Pseudomonas aeruginosa
PC fungal keratitis
less aggressive than microbial keratitis
Usually a history of trauma from vegetation - farmer.
healing takes a long time
orbital cellulitis PC
painful (esp on eye movements) Proptosis Often associated with paranasal sinusitis (although can be insect bite on eyelid traveling backwards) Pyrexial Sight threatening
investigation of orbital cellulitis
Cared for by ENT and Ophthalmology(admit)
CT scan to identify orbital abscesses
how to distinguish between between preseptal and orbital cellulitis
examination. vision (loss of red colour) and painful rectus medial on moving eye. also skin is well marked around orbit in orbital
causative organisms of orbital cellulitis
Staphylococci Streptococci Coliforms Haemophilus influenzae anaerobes
orbital cellulitus treatment
If any suggestion there is restriction of muscles or optic nerve dysfunction then scan (CT)
Broad spectrum AB and monitor closely
Sometimes an abscess will require drainage
what is endopthalmitis? why does it occur?
Devastating infection inside of the eye
Post-surgical or endogenous
PC of Endophthalmitis
Painful +++, with decreasing vision
Very red eye
[Sight threatening]
most common organism causing Endophthalmitis?
Often conjunctival “commensals”
Most common is staph epidermidis
treatment of Endophthalmitis?
Intravitreal(inject eye) amikacin/ ceftazidime/ vancomycin and topical antibiotics
systemic antibiotics too (but due to poor vascular supply not too useful; usually bugs, IS, ABs don’t get to that part of eye - so infection v destructive)
what is Chorioretinitis
inflammation of back of the eye/retina
causes of Chorioretinitis
CMV in AIDS - Haemorrhagic CMV retinitis
Toxoplasma gondii
Toxocara canis (worm)
what is the pizza-pie sign seen in?
Haemorrhagic CMV retinitis in AIDS - not issue due to good HIV treatment
what causes toxoplasmosis? what type of infection is this?
Toxoplasma gondii
protozoal infection
key facts about toxoplasmosis (Chorioretinitis)
Protozoan infection by toxoplasmosis gondii
Cats and raw meat
Mild flu like illness
Rarely causes any further problems
In immunocompetent patients it enters latent phase with cysts forming
Very common- 10% of USA sample had toxoplasmosis specific IgG
treatment of toxoplasmosis Chorioretinitis
only causes problem if macula gets scarred; requires systemic treatment if life-threatening
toxocara canis (worms) keys facts
Parasitic nemotode (roundworm)
Affects cats or dogs
Unable to replicate in humans
Remains an immature form of the worm (larvae)
Often self limiting as they cannot replicate
Form granulomas which can cause irreversible visual loss
how to diagnose bacterial keratitis
corneal scrapes
how to diagnose endophthalmitis
Aqueous/vitreous for culture
how to diagnose acanthamoeba in eye
microscopy/culture
how to diagnose toxoplasma or toxicara in eye
serology
how to diagnose bacterial, viral, chlamydial infection in eye?
Swabs for culture
what is the most commonly used topical antibiotic for the eyes?
Chloramphenicol
how does Chloramphenicol work?
-Inhibits peptidyl transferase enzyme (therefore stops bacterial protein being made)
- Bacterocidal for strep and haemophilus
- Bacterostatic for staph
side effects of Chloramphenicol
Allergy
Irreversible aplastic anaemia (rare : 1 in 40,000)
Grey baby syndrome (build up of Chloramphenicol )
what antibiotics inhibit cell wall synthesis?
Penicillins & cephalosporins have common B lactam ring
B lactam ring inhibits enzyme which makes bacterial cell wall
[Without cell wall, bacteria die]
what is Dacryocystitis?
Dacryocystitis is an infection of the lacrimal sac, (secondary to obstruction of the nasolacrimal duct at the junction of lacrimal sac)
what antibiotics inhibit nucleic acid synthesis?
Quinolones e.g. ofloxacin, inhibit DNA gyrase, an enzyme that compresses bacterial DNA into supercoils
[Inhibition of DNA gyrase leads to unwinding of supercoils and cell death]
when is only case ofloxacin should be used? why?
bacterial keratitis.
to prevent resistance
eye drop bottles don’t keep loner than a month even in fridge(4 weeks) - what is the commonest contaminant
Pseudomonas
how to treat bacterial conjunctivitis?
chloramphenicol
(treats most bacteria except Pseudomonas aeruginosa)
fusidic acid
(treats Staph. aureus)
gentamicin
(treats most Gram negative bacteria including coliforms, Pseudomonas aeruginosa)
what is acyclovir. how is it given? why is it used?
anti-viral, topical/systemic.
used for detritus ulcer in cornea to stop preforation
how does acyclovir work ?
Aciclovir inhibits viral DNA synthesis Base analogue (mimics guanine)
what should not be given to patient with red eye? when can it be?
steroids
can be once slit lamp shows no dendritic ulcer
how to treat Chlamydial conjunctivitis
topical oxytetracycline
but adults may also need oral azithromycin treament for genital chlamydia infection
how to treat bacterial keratitis?
A 4-quinolone (Ofloxacin)
(treats most Gram negative bacteria including coliforms, Pseudomonas aeruginosa, Haemophilus influenzae. Not active vs. Strep. pneumoniae)
Gentamicin and cefuroxime
(the combination will treat most Gram positive and Gram negative organisms but is more toxic to eye itself)
