WEEK 1: Eye infections Flashcards
Define normal flora.
Resident bacteria – Facilitate inhibition of growth of virulent strains.
Conjunctiva - habitat for various resident microorganisms
State the predominant species found in it.
State other species found in it.
Conjuctiva - habitat for various resident microorganisms
Predominant species:
Coagulase negative Staphylococcus i.e.
S. epidermidis
Streptococcus species
Others:
Corynebacterium, Propionibacterium acnes, Staphylococcus aureus, Escherichia coli , Haemophilus & Pseudomonas species
Outline various factors influence indigenous flora.
Environmental factors
Age
Contact lens use.
Immunocompromising disease & medications
The eye is a moist, warm tissue, oxygenated & rich in nutrients. So, without effective host defenses, contaminating microbes would infect frequently.
Outline the Mechanical, anatomical & immunological defense mechanisms of the eye.
- Conjunctiva, eyelids & lacrimal apparatus
Protective structures - Tears
Flush foreign particles; also contain - IgA & IgG; antimicrobial proteins-lactoferrin, lysozyme, lipocalin & beta-lysin.
-Tears contain several antimicrobial molecules attained primarily from the lacrimal gland and surfaces of the eye i.e. cornea, & epithelial cells.
There are also: neutrophils; AMPs = antimicrobial peptides; sIgA = secretory Immunoglobulin A; sPLA2 = secretory phospholipase A2; SLPI = secretory leukocyte protease inhibitor; SP-D = surfactant protein D.
-Tears help to physically wash out invading pathogens & they contain several antimicrobial molecules that are inhibitory to the growth of pathogens.
- Corneal nerves
Relay sensory information leading to reflex movements to protect eye. - Epithelium
Corneal epithelial cells secrete cytokines. - Keratocytes
Under influence of IL-1 & TNF, can synthesize IL-6 & defensins. - Neutrophils
- Cytokines, Complement
- Langerhans cells
Outline the different eye infections for the following parts.
Conjunctiva
Cornea
Cornea & Conjunctiva
Soft tissue around the eye
Vitreous & aqueous humor
Conjunctiva: Conjunctivitis, trachoma
Cornea: Keratitis (abrasions & ulcers)
Cornea & Conjunctiva: Epidemic keratoconjunctivitis
Soft tissue around the eye: Periorbital & orbital cellulitis
Vitreous & aqueous humor: Endophthalmitis
Define Conjunctivitis – ‘Pink / red eye.’
Inflammation of conjunctiva - mucous membrane lining inside of eye lids (tarsal) & sclera (bulbar)
Conjunctivitis can be infectious + noninfectious can be further divided into other types.
Give the examples of the infectious and non-infectious conjunctivitis.
Infectious
*Bacterial
*Viral
Non- infectious
*Allergic
*Nonallergic
Discuss the prevalence of conjunctivitis and the treatment options.
Prevalence of infectious conjunctivitis differs in paediatric vs. adults. Bacterial more prevalent in children
Infectious conjunctivitis is generally self-limiting, but treatment facilitates reduction of transmission.
Define Allergic conjunctivitis.
Outline the examples of allergic conjunctivitis.
Notes: Hypersensitivities to an exposure to an ‘allergen’ on the ocular surface.
It is an IgE mediated hypersensitivity reaction (type I), with resultant mast cell degranulation following direct contact with an allergen on the ocular surface.
Can be acute or seasonal &/or perennial. In many cases the onset of allergic conjunctivitis happens in people younger than 20 years old & then tends to decrease with age i.e. in older populations.
Although allergic conjunctivitis can by itself most times is also associated together with allergic rhinitis, atopic dermatitis &/or asthma.
Allergic conjunctivitis: group of diseases incl.
*Vernal keratoconjunctivitis.
*Seasonal rhinitis.
*Atopic keratoconjunctivitis
*Papillary conjunctivitis
Discuss the following:
*Vernal keratoconjunctivitis.
*Seasonal rhinitis.
*Atopic keratoconjunctivitis
*Papillary conjunctivitis
For further reading please refer to article: ‘Allergic Conjunctivitis’ by Baab, S; Le, P. H.and Kinzer, E. E. (https://www.ncbi.nlm.nih.gov/books/NBK448118/)
Vernal Keratoconjunctivitis
Exact mechanism not well understood, it’s suggested that it is an IgE mediated hypersensitivity with some Tcell involvement.
More common during in warm climates
More common in males. In younger people (<10years) with a history of atopy or asthma
Also tends to decrease with age, in many cases it is completely resolved after adolescence
Atopic Keratoconjunctivitis
Type I & delayed type IV hypersensitivity
In contrast to the previous, it is more evident in older years of age (30-50years)
Associated with atopic dermatitis. Like vernal keratoconjunctivitis, there is a male to female predominance
Giant Papillary Conjunctivitis:
Type I & delayed type IV hypersensitivity
Mostly seen as an aggressive allergic response to contact lenses.
Common in teenagers & young adults
Most commonly seen in conjunctionwith soft contact lens use & observed in ~5% of contact lens users
State the symptoms of allergic conjuctivities.
Symptoms
-Bilateral redness; intense itching; watery discharge; follicles & papillae in conjunctiva (‘cobblestone appearance’)
In extreme cases: chemosis i.e. bulging, oedematous conjunctiva extending beyond eye lid level & maybe dark patches under eyes)
May occur at specific times of the year e.g. during periods of high levels of pollen or specific allergy e.g. cats
Outline the causative agents and treatment of allergic conjunctivitis.
Causative factors:
-Airborne allergens contact eye, causing type I hypersensitivity, triggering local mast degranulation & release of mediators e.g. histamine, eosinophil chemotactic activating factors
Treatment is primarily supportive measures i.e.
*Cold compress
*Artificial tears.
*In some cases, topical or oral antihistamines and mast cell inhibitors may also be prescribed
*Largely supportive but topical corticosteroids beneficial in severe cases
Discuss the causative agents, symptoms and treatment of Non-allergic/ Irritant Conjunctivitis.
Cause-usually transient.
Mechanical trauma or chemical exposure or other various irritants causing inflammatory response e.g. smoke, chlorinated pool H2O, shampoos), eyelashes.
Symptoms (usually improve within 24hours)
-Discharge watery
-Intermittent redness
Treatment - cleansing of eye to remove irritant.
The presentation now moves onto microbial infections of the eye, starting with those of the conjunctiva which, can be broadly categorized as:
- Bacterial conjunctivitis
- Viral conjunctivitis.
- Bacterial conjunctivitis
-Usually, a bilateral suppurative ocular infection resulting in purulent discharge.
-Treated with antibiotic eye drops.
- Viral conjunctivitis
-Usually starts as a unilateral infection that becomes bilateral after few days.
-Resulting in tears & watery discharge.
-Normally self limiting, with supportive management
Discuss Ophthalmia neonatorum.
Ophthalmia neonatorum - treated as an emergency
Rare ocular infection in new-Borns
Acquired via vertical transmission i.e. vaginal delivery from the mother with an untreated sexually transmitted infection
Treated as an emergency to prevent permanent eye damage or blindness.
Outline the major causes of ophthalmia neonatorum.
- Chemical
- Bacterial: Neisseria Gonorrhea, Chlamydia trachomatis, H. Influenza, Step. Pneumoniae
- Viral: Herpes simples, adenovirus
Discuss the management of hyperacute conjunctivitis.
Gonococcal ocular infection will include treatment would need to include both mother and baby:
-Intramuscular ceftriaxone for adults, children & neonates
&
-Oral azithromycin or doxycycline for adults (& erythromycin –neonates)
Due to increased rates of antimicrobial resistance in N. gonorrhoeae, the Centers for Disease Control & Prevention treatment 2015 guidelines support dual therapy with ceftriaxone & azithromycin.
As with Gonococcal conjunctivitis, neonates are mostly infected with Chlamydial conjunctivitis during delivery (from an infected mother) but they can also be infected after delivery by nursing mother.
Similar treatment as above
Discuss acute conjuctivitis.
Signs and symptoms
Causative pathogens
Common, contagious, higher incidence & prevalence in children (particularly infants, school children) & elderly
Symptoms
*Eye redness
*Mucopurulent discharge – thick yellow, white or green (vs. watery in viral). Usually, one eye but may be bilateral.
*Eyes may be ‘stuck shut’ especially in mornings
Causative pathogen
*Staphylococcus aureus – (esp. adults)
*Streptococcus pneumoniae (in children)
*Haemophilus influenzae (in children)
*Moraxella catarrhalis (esp. in children)
*Pseudomonas aeruginosa
~a 1/3rd acute infectious conjunctivitis cases are caused by bacteria: Staphylococci species are the most common pathogens, followed by
followed by Streptococcus pneumoniae and Haemophilus influenzae.
But in children, the leading causes of these infections are S. pneumoniae, H. influenzae, or Moraxella catarrhalis.
Recall: If the onset is hyper acute in neonate, the leading causative pathogens are: Neisseria gonorrhoeae or Chlamydia trachomatis.
Discuss the management of bacterial conjunctivitis.
HIGHLY CONTAGIOUS:
Management = prevent spread + treat infection
- Standard ‘Infection control measures’ i.e. continual hand sanitization; avoid sharing of hygiene cloths.
- Broad spectrum topical antibiotic i.e. eye drops or ointment
Chloramphenicol
Fusidic acid
In most cases self-limiting, 60% of cases will resolve within 5 days without antibiotic interventions.
Discuss Viral conjunctivitis.
1. Causative pathogen
2. Transmission
3. Symptoms
Causative pathogen
Most common cause (60-90%): Adenovirus
Less common - Herpes simplex virus type 1; Varicella-zoster virus; Measles virus
Contagious especially in first ~2 wks (& may last up to 2-3wks)
May occur with or just after common colds & systemic viral infections
(i.e. measles, chickenpox, rubella & mumps.
Localised viral conjunctivitis without systemic manifestations usually results from adenoviruses
Transmission:
-Direct contact of tears or eye discharge
Symptoms
-Significant eye redness + very watery
-Chemosis ; preauricular lymph node may be swollen
-Tarsal conjuctiva may have follicular or ‘bumpy’ appearance-gritty feeling
Disease often becomes bilateral in 24 - 48hrs.
Self-limiting infection
Discuss clinical presentation in both bacterial & viral conjunctivitis vs keratitis.
*Visual acuity is preserved
*Photophobia absent
NB.
Presence of either photophobia or decreased visual acuity triggers concern for corneal involvement.
Corneal involvement has more dire prognosis & requires ophthalmologic consultation.
Discuss Allergic Conjunctivitis - Management.
*Diagnosis extensively by clinical history & clinical examination.
*Swabs & laboratory cultures rarely performed.
Focus is on alleviating discomfort.
-Mild cases - cold compresses on eyes & artificial tears
-Vasoconstrictors - antihistamine combination for severe pruritis
-Anti inflammatories i.e. steroid eye drops
Antibiotics
Strict hygiene is vital – hand washing / sanitising
Avoiding sharing personal articles & contact with others
Conjunctivitis often self-limiting BUT early & correct diagnosis vital, to rule out medical emergencies i.e. bacterial keratitis, corneal abrasions, acute closed angle glaucoma.
Discuss Conjunctivitis - Management
1. Viral conjunctivitis (most common):
2. Bacterial conjunctivitis (less common):
In certain cases, treatment:
Viral conjunctivitis (most common): no specific
-Antiviral treatments but for Herpes simplex or zoster virus then antivirals are prescribed i.e. Acyclovir ointment or Ganciclovir gel
Bacterial conjunctivitis (less common):
-Antibiotics not generally prescribed
-But if prescribed: chloramphenicol 0.5-1% eye drops -Fusidic acid
They both prevent the synthesis of bacterial protein.
In most cases self-limiting, 60% of cases will resolve within a week without antibiotic interventions.
If condition doesn’t improve in approx. referral to ophthalmologist necessary
Discuss management of Gonococcal ocular infection.
Gonococcal ocular infection will need treatment.
If suspected, conjunctival swabs collected for lab testing.
Must be immediately referred to ophthalmologist.
*Intramuscular ceftriaxone recommended for adults, children & neonates
*Patients should lavage infected eye with saline
Discuss management of Chlamydial ocular infection.
*Many cases have concurrent genital infection
*If suspected, conjunctival swabs collected for lab testing
- Oral azithromycin or doxycycline for adults ( & erythromycin –neonates)
Due to increased rates of antimicrobial resistance in N. gonorrhoeae, the Centers for Disease Control & Prevention treatment 2015 guidelines support dual therapy with ceftriaxone & azithromycin.
Define keratitis.
Inflammation of cornea, most often by a bacterial or viral infection.
Why is Viral & Bacterial keratitis considered serious ocular infections?
Because can cause of corneal opacifications & if untreated common cause of blindness world-wide after cataracts.
Outline Risk factors: ***Most common pre-disposing factors of Keratitis.
*Overuse of contact lenses, esp. overnight
*Ocular surgery
*Use of topical corticosteroids
*Abrasions (physical &/or chemical) on cornea, *Refractive surgery
*Diabetes
*Topical steroids
*Trachoma
*Exposure to intense ultraviolet light,
Outline symptoms of keratitis.
*Acute redness
*Tearing
*Painful eye
*Often with a foreign body sensation
*Photophobia
*Decreased vision
Prompt diagnosis, identification of causative agents & treatment paramount. To prevent vision loss due to ulceration, necrosis & scarring***
Outline Common bacterial pathogens for Keratitis.
Staphylococcus spp.
Streptococcus pneumoniae
Pseudomonas spp.- esp. amongst contact lens wearers
Moraxella catarrhalis-immunocompromised patients
Neisseria gonorrhea & Chlamydia trachomatis: sexually active patients esp. if conjunctivitis is present:
