Infections of the Sensory System Flashcards
What are the non-specific defense mechanisms of the eye?
- bony orbit, muscles and eyelids
- tears and tear film (corneal epithelium, aqueous water layer, outer lipid layer)
- ocular epithelium
- normal ocular bacterial flora
- mucin
- antibacterial factors
- macrophages and NK cells
What are the specific defense mechanisms of the eye?
- eye-associated lymphoid tissue (generates immune response in lacrimal gland, lacrimal sac and lining the conjunctiva of the eye)
- Langerhan’s cells
- immunoglobulins
- T and B lymphocytes
What are the important proteins in infection response?
Lysozyme: important in the primary response to infection. Found in tears, saliva and mucus. Can break down the peptidoglycan in the cell wall of gram positive bacteria. Also found in macrophages and neutrophils.
Lactoferrin: found in tears, saliva and mucus. Can bind iron starving bacteria and fungi from it (needed for its metabolism) and can also break down DNA and RNA (anti-viral). Found in neutrophils.
What is the normal microbiota of the eye?
- staphylococcus
- streptococcus
- corynebacterium
- propionibacterium
Conjunctivitis
Viral:
- causes: coronavirus, rhinovirus, RSV, parainfluenza
- signs: sticky, watery, pink eyes
- treatment: self-limiting
Adenoviral conjunctivitis (more serious):
- signs: bilateral red, sticky, painful eyes, enlargement of ipsilateral periauricular lymph node, starts with sore throat and cough
- treatment: symptomatic - paracetamol, lubricating drops
Bacterial:
- causes: H. influenzae, S. pneumoniae, moraxella
- signs: like viral but with yellow thick discharge
- treatment: chloramphenicol, fusidic acid
Keratitis
corneal infection caused by breach of normal defense (tear film deficiency/eyelid dysfunction/exogenous/endogenous)
Bacterial (associated with contact lens wear):
- causes: S. aureus, S. pneumoniae, pseudomonas spp.
- signs: yellow infiltration of cornea, redness of sclera
Viral (usually unilateral):
- causes: HSV
- signs: painful, red, watery eyes. Photophobic. Dendritic ulcers which can increase in size and cause scarring
- treatment: topical and oral aciclovir
Orbital cellulitis
Serious.
- pre-septal: caused from scratches/insect bites/local spread of infection
- post-septal: from secondary spread (sinusitis/local trauma), can cause abscesses and cavernous sinus thrombosis
- treatment: systemic antibiotics
Trachoma infection
- cause: chlamydia trachomatis
- signs: follicles in upper conjunctiva causing inflammatory thickening, scarring and inward turning of eyelids.
- follicles can cause abrasion to the cornea eventually resulting in blindness
- treatment: surgery, antibiotics, improved facial hygiene
Endophthalmitis
- causes: intra-ocular operation, trauma with inoculation of foreign body, complication of systemic infection
- treatment: intra-ocular and systemic antibiotics with or without vitrectomy
Otitis media
- causes: RSV, can be S. pneumoniae and H. influenzae
- symptoms: fever, diarrhoea, vomiting, headache, earache
- clinical signs: fluid in middle ear, bulging ear drum, hole in tympanic membrane with pus
Otitis externa
- causes: S. aureus, candida albicans, pseudomonas aeruginosa
- clinical signs: wax, chronic inflammation, fungal spores, foreign bodies
Sinusitis
- causes: pathogen invasion of middle/outer ear or sinuses causing block of eustachian tube or sinuses (RSV, S. pneumoniae, H. influenzae)
- can cause mucosal swelling and impaired mucociliary clearance
- acute signs: facial pain with localised tenderness
- treatment: ampicillin, amoxycillin, oral cephalosporins
Acute pharyngitis
- causes: EBV, CMV, S. pyogenes
- symptoms: headache, fever, malaise
- CMV can be mild/asymptomatic
- EBV: palatal petechiae, cervical lymphadenopathy, splenomegaly
- treatment: ganciclovir, cidofovir
Tonsilitis
- cause: S. pyogenes
- signs: fever, sore throat, enlargement of tonsils, tonsillar lymphadenopathy
- treatment: penicillin
Parotitis
- causes: mumps virus
- signs: pain and swelling of parotid gland, trismus, malaise
- treatment: mouth care, nutritional, analgesia
