Infections of the Sensory System Flashcards
What are the nonspecific ocular defences?
Eyelids, tears, ocular epithelium, normal ocular bacterial flora, mucin, antibacterial factors and macrophages and natural killer cells.
What are the specific ocular defences?
Eye-associated lymphoid tissue, Langerhans’s cells, immunoglobins, T-lymphocytes and B-lymphocytes. The bony orbit is the first line of defence as it protects the eye from trauma. The tear film (thin aqueous layer) and cornea. Ocular lymphoid tissue (lacrimal gland associated lymphoid tissue, conjunctiva-associated lymphoid tissue and lacrimal drainage-associated lymphoid tissue)
What are some biomolecules that are involved in defence against infections in the eye
Lysozyme - Enzyme that cleaves peptidoglycan. It can be found in tears, saliva, mucous and intracellularly in macrophages and neutrophils
Lactoferrin - Binds iron which starves bacteria and fungi. It also breaks down RNA and DNA making. Found in tears, saliva, mucous and neutrophils.
Both help defeat gram negative bacteria
Describe features of the ocular biome
- Staphylococcus, streptococcus, propionibacterium and corynebacterium.
- Works via competitively inhibits growth of pathogenic organisms
Name the common and rare eye infections
Common - Conjunctivitis, keratitis and orbital cellulitis.
Rare - Endophthalmitis, and retinochoroiditis.
Describe the features of viral conjuntivitis
Can be caused by; coronavirus, rhinovirus, RSV or parainfluenza virus (also adeno but this is more severe)/
It can cause symptoms of; Sticky, watery, pink eyes but it is a self limiting illness which tends to get better on its own
What is significant of adenovirus conjunctivitis?
More serious. It causes bilateral, very sticky, red, painful eyes. Can have corneal involvement resulting in punctate keratitis. Presents with sore throat and cough and enlargement of ipsilateral periauricular LN. The keratitis can last a long time.
Describe features of bacterial conjunctivitis
Discharge appears more yellow adn thick than viral and typically won’t go away without antibiotic treatment.
The common causes are haemophilus influenzae, streptococcus pneumoniae and moraxella. Treat with chloramphenicol or fusidic acid.
How can neonatal conjunctivitis develop?
If the mother has a sexually transmitted infection at the time of birth. Causative organs are neisseria gonnorhoea, chlamydia trachomatis or haemophilus influenza streptococcus
What is keratitis and causes?
It is corneal infections which can be caused by bacterial organisms (most often contact lens related in the UK), viral (HSV and HZO) or trachoma.
What are the common causes of corneal ulcers?
- Tear film deficiencies,
- Eyelid malformation/dysfunction,
- Endogenous cause,
- Exogenous cause (main bacterial corneal ulcers are caused by S. aureus, S. pneumoniae or pseudomonas spp)
Describe features of HSV keratitis
- presents with history ‘cold sores’
- Always unilateral and can be recurrent.
- Painful, red, watery and photophobic.
- Treat with topical and oral aciclovir
Describe features of orbital cellulitis
Can be pre/post septal. Preseptal is common and can result from scratches, insect bites or local spread. Postseptal arises from secondary spread and complications can be abscess and cavernous sinus thrombosis.
Eyelid oedema and erythema or failure to respond to abx is RED FLAG
Describe features of trachoma
Caused by a chlamydia trachomatis infection which causes chronic keratoconjunctivitis. Main viral cause of blindness.
S- surgery for interned eyelids.
A - antibiotics.
F - Facial cleanliness to prevent transmission.
E - Environmental change
What is onchocerciasis?
Parasitic infection which causes skin lesions and eye lesions which could lead to blindness
What are the ocular manifestations of HIV/AIDS
Tuberculosis, toxoplasmosis (anti-parasitic, antibiotics and corticosteroid treatmetn), CMV (cytomegalovirus retinitis presents late in course of HIV disease, treated with Ganciclovir), mycobacterium avium complex, cryptococcosis and microsporidiosis
Describe features of endophthalmitis
- Inflammation of intraocular fluids.
- Develops after intra-ocular op eg, cataract surgery, trauma with inoculation of foreign body or complication of systemic infection.
- Treated with intra-ocular and systemic antibiotics with or without vitrectomy (removal vitreous fluid)
What are the defence mechanisms of the upper respiratory tract?
Innate - Physical, cells and chemicals (ear wax is antibacterial).
Adaptive - T cells, B cells and antibodies
Explain the bony protection of the hearing system?
Pinna - hollow folds and contours of the outer ear funnel and enhance the sound waves.
Describe features otitis media?
Most common in infants and small children, mainly RSV but could also be s. pneumoniae and h. influenzae.
Clinical features - fever, diarrhoea and vomiting, headaches and earache.
May result in hearing difficulties and delayed learning development.
Describe features of otitis externa
Cam be caused by staphylococcus aureus, candida albicans or pseudomonas aeruginosa.
What is sinusitis?
Pathogen invasion of air spaces associated with URT (middle ear, outer ear and sinuses). The mucosal swelling prevents muco-ciliary clearance of infection
What are the common causative agents of sinusitis?
- Respiratory syncytial virus (RSV),
- Mumps virus,
- Streptococcus pneumoniae,
- Haemophilus influenzae,
- Bacteroides fragilis
What are the clinical features and treatments for sinusitis?
Features - facial pain and localised tenderness.
Treatment - Ampicillin, amoxycillin, oral cephalosporins
Describe features of the common cold
Transmitted by aerosol or virus contaminated hands. Caused by rhinovirus and coronavirus (main ones), coxsackie virus A, echovirus or parainfluenza.
Causes tiredness, slight pyrexia, malaise, sore nose and pharynx, profuse, watery nasal discharge becoming mucopurulent, sneezing in early stages. Secondary bacterial infections can occur in minority
What are the causative agents in acute pharyngitis and tonsillitis
Viral - Epstein-Barr virus and Cytomegalovirus.
Bacterial - Streptococcus pyogens
Describe features of cytomegalovirus
Transmitted in body secretions and organ transplants. The virus can reactivate and cause disease when cell-mediated immunity is compromised. Treated with ganciclovir, foscarnet or cidofovir.
Describe features of the Epstein Barr Virus
Glandular fever, replicates in B lymphocytes.
Clinical features - Fever, headache, malaise, sore throat, anorexia, palatal petechiae, cervical lymphadenopathy, splenomegaly and mild hepatitis
Contact sports should be avoided until splenomegaly resolved. Complications are Burkitt’s lymphoma, nasopharyngeal carcinoma and guillain barre syndrome
Describe clinical features of tonsilitis
Bacterial tonsillitis is caused by streptococcus pyogenes. Results in fever, pain in throat, enlarged tonsils, tonsillar lymphadenopathy. Susceptible to treatment with penicillin.
What are the complications of streptococcus pyogenes?
Scarlet fever (caused by erythrogenic toxin), peritonsillar abscess, otitis media/sinusitis, rheumatic heart disease or glomerulonephritis
What are the features of parotitis?
Caused by the mumps virus. Symptoms are fever, malaise, headache, anorexia, trismus, severe pain and swelling of parotid gland.
Treatment - Mouth care, nutritional and analgesia.
Prevention - Active immunisation (MMR vaccine)
Complications - CNS involvement, epididymo-orchitis
Describe features of acute epiglottis
Caused by haemophilus influenza. Clinical features are high fever, massive oedema of the epiglottis, severe airflow obstruction resulting in breathing difficulties and bacteraemia.
DO NOT examine throat or take swabs as this will precipitate complete obstruction of airway. Instead blood cultures to isolate H.Influenzae
Treatment - Life-threatening emergency which requires urgent endotracheal intubation and IC ABX (Ceftriaxone or chloramphenicol)
Describe features of diphtheria
- Corynebacterium diphtheriae.
- Causes sore throat, fever, formation of pseudomembrane, lymphadenopathy and oedema of anterior cervical tissue.
- Treatment is prompt anti-toxin therapy administered intramuscularly, concurrent antibiotics and strict isolation.
- Prevention via childhood immunisation with toxoid vaccine
Describe features of laryngitis and tracheitis
Infections may spread down from the URT. They are usually viral in origin ( Parainfluenza, respiratory syncytial, influenza or adenovirus)
In adults this may cause hoarseness and retrosternal pain.
In children it may cause dry cough and inspiratory stridor
