Infections to the eye Flashcards
What are the peripheral infections to the eye
Peripheral infections of the eye Molluscum contagiosum, staphylococcus
give an example off an eyelid infection to the eye
staphylococcus aureus
where does staphylococcus aureus coccur
Multiplies in hair follicles (eye lashes)
Can produce infection and swelling of the eyelid known as a STYE
If touched like a solid mass
Can be opened with a scalpel – will release pus and a core (a white pea-like mass)
Likely go away over time
if there is a persistent infection of staph what happens
However, a persistent infection sees extended pathology – Blepharitis
Edges of eyelids become red and swollen
what does staph look like when stained
Pus from lesion on slide then Gram stained and visualised by microscopy:
Numerous polymorphonuclear (PMN) cells
Immune cells which kill and digest bacteria
Dead PMNs, tissue debris and bacteria produce pus
Gram +ve cocci in clumps
Staphylococci
when staph is smeared onto agar plate what happens
Swab smeared on to plate
Start with confluent layer of bacteria
Can produce single colonies
One bacteria starts, doubling every 20 minutes produces a colony
One colony ~1x109 bacteria
Staphylococci grow as pale, circular colonies on BcVod agar plates
Colonies with a yellow tinge – almost gold – Staphylococcus aureus
what properties of staph differentiate it from less non pathogenic species
Staphylococcus aureus has properties which differentiate it from less or non-pathogenic species
Non-pathogenic staphylococci lack invasive weaponry to cause disease
Pathogenic Staphylococcus aureus produce toxins and enzymes (e.g. coagulase), which confer pathogenicity
Coagulase is an indicator of the presence of other toxins and invasins
what is the ball found in a infected hair follicle called
Coagulase – enzyme which coagulates plasma
Cleaves fibrinogen to fibrin
If added to plasma it will clot
Ball found in infected hair follicle is a coagulant
If press on stye can express coagulant as one drop
Once removed no need for further treatment – will heal
how would they track staphloccoi outbreaks in wards
Further typing of staphylococci may be required to track outbreaks within wards
40% carry S. aureus asymptomatically
Increases to 60% in hospital settings
Carriers can easily become dispensers
Factors like having a cold etc. lead to spread
Whole genome sequencing
Rapid and cost-effective
Search for specific changes in seven key genes
Specific changes allow grouping of S. aureus isolates
what are the diff types of conjunctivitis
Neisseria gonorrhoeae
Haemophilus influenzae
Staphylococcus aureus
Pseudomonas aeruginosa
Streptococcus pneumoniae
what is nesireera gonorrhoea
Causative organism of gonorrhoea
Prevalence rising again due to antibiotic resistance
Symptoms are gender specific
Male – extreme pain during urination, purulent discharge
Female – can be aymptomatic
Considered carriers (clinical perspective)
Infection can increase without knowledge causing core pelvic disease
If infection moves to fallopian tubes can lead to sterility
Infection contracted at birth from mother’s genital tract: occurs from 1-5 days of age
what type of infection is neisseria gonnorhoea
Hyperpurulent infection
Pus from the eye placed on a slide and Gram stained shows:
Numerous pus cells
Gram –ve diplococci occurring inside the pus cells
Neisseria
how is neisseriha goner differentiated from other neiseriria
Two members of genus considered pathogenic
Neisseria gonorrhoeae differentiated from other Neisseria by biochemical tests
what does neiserria grown on chocolate agar show
Neisseria grown on chocolate agar shows small, white circular colonies
Treatment – Rapidly required to stop irreversible vision impairment through corneal ulceration
Used to treat with penicillin or chloramphenicol ointment
what is done if there are cases of neisseiheara gonohrea
N. gonorrhoeae infections are reportable to PHE
Isolate is tested for antibiotic resistance using E-test
Used to be given chloramphenicol eye drops
N. gonorrhoeae rapidly developed resistance to penicillin and chloramphenicol
Now recommended to give an injection of ceftriaxone
what is haemophilius
Infection by Haemophilus influenzae can occur at any age, either sporadically or as an outbreak involving a number of persons
Isolated from influenza patients in 20th century – originally thought to be causative agent
Actually cause of secondary pneumonia leading from influenza
Pus from the infected eye placed on a slide and Gram stained:
Pus cells
Gram –ve rods, which are PLEOMORPHIC (some very short-like cocci and some long rod shaped)
for growth what does haemophiliac require
For growth Haemophilus requires Haematin (found in blood) and/or NAD+ produced by staphylococci (obtained from a supplied source)
Struggles to grow on blood agar
Haematin and NAD found within cells
Heat blood agar to lyse cells, Haemophilus can grow
On blood agar, Haemophilus influenzae grow as satellite colonies around staphylococci – termed Satellitism
how many type of pathogenic species of haemophiliac occur
3 pathogenic species of Haemophilus occur and are identified by Haematin and/or NAD+ requirement
Only Haemophilus influenzae typically causes conjunctivitis
what is sticky eye infection on neonates due to staphylococcus called
Sticky-eye’ infection in neonates due to Staphylococcus is a conjunctivitis
Occurs 5-10 days after birth
Associated with an outbreak of staphylococcal infection in a maternity unit
Introduction of bacteria from patient’s nose or skin by fingers
Treat with appropriate antibiotics as infecting agent is commonly resistant to some antibiotics
For diagnosis and AMR detection, see earlier slides
Resistance is now a critical issue
Emergence of MRSA and now VRSA
Rapidly running out of effective antibiotics
what is pseudomonas aeurginso
Pseudomonas aeruginosa is not an invasive pathogen
Commonly found in soil and water (baths/sinks/toilets/eye drops/soap dishes)
Can infect the eye after trauma
Eye surgery, presence of a foreign body or suppressed immune status within the patient
Contact lens
Accumulation of infected pus containing Gram –ve, rod-shaped bacteria
what is the best treatment for pseudomas aeuroginosa
When grown on simple nutrient agar, produce a blue green fluorescent pigment – only bacteria with this property
Difficult to treat as it has innate resistance to a wide range of antibiotics – environmental bacteria
Best treatment is prevention
Elimination or control of potential sources on wards, theatres and outpatient departments
what can sreptoccusi pnueominae cause
Streptococcus pneumoniae can cause pneumonia or meningitis
Asymptomatic carriage in the throat
Traversal to lungs causes pneumonia
Causes keratitis either following injury or by invasion
Introduced from the throat (coughs or fingers)
Accumulation of pus
what Does streptococcus pneumoniae look like on a agar plate
Pus on slide, Gram stained and viewed by microscopy:
Pus cells
Gram +ve
Diplococci
Surrounded by clear, unstained space which mark the presence of capsule
Capsule allows bacteria to invade tissues and resist phagocytosis
Growth on agar plate
Loss of capsule loss of virulence
Colonisation of body leads to a re-established capsule
how is streptococcus pneuominiae viewed on blood agar
Grown on blood agar and in the presence of optochin
Colonies show α-haemolysis
Hydrogen peroxide produced by bacteria, oxidises haemoglobin, blood cells turn green beneath bacteria
Blood cell is fragile and may lyse thinning blood around the bacterial colony
Sensitivity to optochin allows for specific identification
Other Streptococci resistant
Sensitive to penicillins
what is leptospira
Common infection of rats
Systemic infection of the rat, excreted in faeces and urine
Proximity of rats to water often means water sources are colonised
Rivers, streams country parks, lakes
Swimming in contaminated water can lead to infection
Swallowing of water, contamination of mucous membranes or through breaks in the skin
2-4 week incubation period, clinical multi-organ infection occurs, known as Weil’s disease
Liver infection leads to cell destruction and jaundice
Evidence of infection is seen in the eyes where bleeding, yellowing and vision impairment manifest
what is an example of an inner eye infection
leptospira
what does histology of leptospirosis show and how is it treated
Histology shows infiltration of the eye by numerous corkscrew-shaped (Spirochete) bacteria together with cellular invasion
Leptospira interrogans
Severe immune response
Can severely impair vision and lead to blindness
Treated with doxycycline or penicillin
what is syphillis
Syphilis is a sexually transmitted infection, increasing in prevalence
Primary syphilis - Flat ulcer appears on genitalia
Corkscrew organisms called Treponema pallidum
50% of cases heal spontaneously
Secondary syphilis – Dissemination of organism from primary ulcer throughout the body causing a widespread rash – may present with a wide range of symptoms
Tertiary syphilis – Continuation of secondary stage alongside infection of neurons and a severe immune reaction – neurological symptoms such as Tabes Dorsalis and general paralysis of the insane
Chronic persistent infection of women
Can lead to stillborn births
Can result in birth of child with irreversibly damaged eyes
Retinitis
Interstitial keratitis can lead to blindness and potentially death
what Is chlaymida trachomatis
Bacteria
Inability to produce energy
Parasitise cells
Grow and multiply inside host cells
Use host cells to produce energy allowing function of enzymes
Common
Associated with STI
Can be aymptomatic
10% of women subclinical infection which can be dangerous to child being born
Three forms of infection
Genitourinary
Pulmonary
Ocular
Develops after infection from mother at birth (similar to N. gonorrhoeae)
A kerato conjunctivitis occurring at 4-7 days of age
what are some of the key characteristics of chalymdia trachmomatis
Most common but treatable cause of blindness in the world
Thickening of eyelids, inner eyelid becomes abrasive
Untreated or repeated infection leads to scarring of the inner eyelid, leading to distortion
Eyelid everts, forcing eyelashes to irritate and damage the eye
Scratching of eye leads to secondary infections and blindness
can chlaymida trachmoatis grow on agar
Can’t grow on agar
Chlamydia grown on tissue cultures
Infected cells contain Chlamydia inclusion bodies
Stained with antibody linked to fluorescent dyes
Very preventable
Infection treated with azithromycin
Antibiotic eye drops also recommended
what is rubella
Mild infection caused by Rubella virus – German measles
Previously very common – now covered by vaccines
Contracted as a droplet infection
Incubation period 14-21 day
Onset – low grade fever and catarrh for 2 days
Prodromal symptoms – non-specific symptoms followed by classical symptoms
Rash – maculopapular, begins on face and neck
General lymphadenopathy
Some cases mild with no rash
Many cases sub-clinical – produce lifetime immunity with no symptoms
is rubella symptomatic in children
Very mild or asymptomatic infection in children
Symptoms usually worse in adults
Extremely serious if infected whilst pregnant
Miscarriage or congenital rubella syndrome (CRS)
how is rubella transmitted
Virus can pass across the placenta and infect the foetus
First trimester – 90% will suffer Rubella syndrome
Second trimester – 20%
Third trimester – quite rare
Whole host of symptoms
Mental incompetence
Microcephaly
Cerebral palsy
Deafness
Congenital heart disease
High proportion of miscarriage
what happens to foetus when rubella occurs in womb
In womb, every pore, gland and fluid exudes virus – completely takes over
Foetus surrounded by a cloud of virus
Exist in a cocoon of perpetual infection
what eye conditions does rubella syndrome include
Rubella syndrome includes cataracts and glaucoma
Irreversible
Very common in CRS
Preventable
MMR vaccine
what is adenovirus
A group of 42 viruses sharing a common structure
Electron microscopy
12 triangular plates in geometric pattern
Stalks from each corner
Proteins in white are same across all 42 strains
Hexons – Six proteins touching each white ball
Pentons – Corners can only house 5 proteins
Proteins in black differ – 42 different forms
Penton base with fiber
Infection from one will not give immunity to others
how many different groups are there in the pathogenesis of adenovirus
Three different groups in pathogenesis
First group – More severe form of a cold
Common cold
Trivial infection - 2/3 days
No temperature/fever
Infection of nasal passages – mucus produced – irritates throat
Symptoms from immune response
Adenovirus colds
Respiratory and influenza like symptoms
7-8 days
Glands swell
Infection of throat and nasal passages
what is the second group of adneovirus characterised by
Three different groups in pathogenesis
First group – More severe form of a cold
Common cold
Trivial infection - 2/3 days
No temperature/fever
Infection of nasal passages – mucus produced – irritates throat
Symptoms from immune response
Adenovirus colds
Respiratory and influenza like symptoms
7-8 days
Glands swell
Infection of throat and nasal passages
Mild infections – troops often vaccinated against
describe the characteristics of adenovirus
Shipyard Eye’
Complaint in shipyard workers and metal workers
Eye infection with no pharyngitis
Intense inflammation in one or both eyes
No infection in families
Atmosphere full of microscopic metal particles
Cause trauma in the eye
Contact with adenovirus infected patient causes spread
Problem in eye clinic
Examination involves slight damage to eye
Patient with Shipyard Eye can easily transmit to other patients
Eye throat
Infections must run course
what is mollusc contagniosum
Poxvirus
Common in young children
Causes small bladder-like lesions on the neck, arms or legs
If opened – no pus
Usually painless
Can last up to 2 years
Eventually recognised and removed by the body
where does mollisum contagious occur In the eye
Occasionally occurs on eyelids
Look like a stye
Unlike staphylococci, not solid
Almost balloon like
Best to leave alone, reversible
how does mulluscum look like under electron microscope and how is It treated
Material from lesion does not contain pus
Unlike staphylococci
Under the electron microscope:
Large brick-shaped virus particles
No treatment, should resolve spontaneously
what is sars - cov- 2 linked to
Emerging evidence that it may cause conjunctivitis
Important to continue all safety measures during examinations
Mucous membranes of the eye considered a pathway to infection
People with glasses 2-3 times less likely to contract
what is herpes simplex 1
Herpesviridae – 8 known to infect humans
Herpes simplex (HSV-1) – most common
Primary infection usually children 6 months - 5 years old
Acquired by contact from patients or carriers
Produces a blister/ulcer on the mouth (cold sore), face etc.
Virus retreats to ganglia – can periodically reactivate
Often passed to children – when adults secreting virus
Cold sore and kissing newborn
what are the characteristics of herpres simplex 2
Lesion normally forms on lips – very itchy
Can be transferred by rubbing/scratching to other skin surfaces, e.g. near the eye
Secondary lesions
Can also be transferred directly to the eye
what can herpes simplex cause
Can cause
Conjunctivitis
Dendritic ulcers
Keratitis
Blindness
Most common infective cause of blindness in high income countries
Corneal graft may be required
what can herpes simplex be treated with
Can be treated with aciclovir
Analogue to nucleotides
Inactivates viral DNA replication
Very potent
Non-toxic
No resistance
Affects majority of herpesviridae
Available over the counter at pharmacists
Initial ‘tingle’ 48 hours prior
Treatment will abort infection
what are the characteristics of varicella zoster (chicken pox)
Herpesviridae
Spread by inhaling virus
Dried from lesions or as droplets
Incubation period of 14-21 days
Manifests in outbreak of respiratory symptoms and rash
Face and in hair, central body more than hands and feet
Vaccine available, not used in UK
Immunocompromised may be offered
Can cause haemorrhagic chicken pox
what are the lesions produced by varciella zoster like
Individual lesions are like blisters
Very itchy
Following recovery, virus remains in the dorsal root ganglia for life
Can also retreat to other ganglia
Doesn’t usually reoccur
what is varicella zoster
In later life, virus is reactivated to produce shingles
Multiplies within the nerves
Intensely painful rash which follows the nerve
Manifests on skin associated with tight clothing
No treatment for it
Aciclovir can reduce symptoms
what are characteristics of varicella zoster
Occasionally can reactivate from facial ganglion (trigeminal nerve)
Large rash across face – demarcation due to infection of specific nerve
From here can spread to eye
Very damaging but quite rare
Virus can travel along the optic nerve to the brain to cause encephalitis
what can amboema cause
Some free-living amoebae can cause keratitis – quite rare
Acanthamoeba
Usually associated with contact lenses which have not been cleaned with sterile saline solutions – enter after trauma to eye
Amoebae found in plain tap water
Must not use for cleaning contact lens or equipment for examining eyes
Very difficult to treat
what is onhoerca volvulus
Microscopic African worm living in freshwater rivers
99% of infected people live in 30 countries across sub-Saharan Africa
37 million people in East and Central Africa are carriers
800,000 blind
Eaten by simulian flies and transferred to humans through insect bites
Parasite multiplies at site of bite to cause swelling, nodules protect parasite from immune response
Parasite produce embryonic larvae which migrate to all organs of the body
what does onchohera volvulus cause
Migrating larvae die and initiate an intense immune response
In skin, intense itching, swelling and inflammation
Can penetrate all areas of the eye
Often migrates to surface of the cornea causing keratitis
Eventually leads to blindness
River blindness
in what populations does onchohererca volvulus occur
Can occur in >90% of adults in some African tribes
Younger generations required to lead infected generation
Proximity means high likelihood of passing on the parasite
Also found in Yemen, Brazil and Venezuela
No vaccine or medication to prevent infection
Best option is prevention
Ivermectin can kill larvae but not adult worms (6-12 months)
what is toxocara
Parasitic roundworm of cats and dogs, eggs excreted in faeces
Spread to humans through ingestion of eggs
Children in parks
Larvae can migrate throughout body causing a severe allergic reaction
Parasitic larvae can encyst within the eye
Can form a granuloma, and cause a peripheral eosinopimulia
Mass (granuloma) often confused with malignant retinoblastoma
Loss of vision over days or weeks
Damage is permanent, can result in blindness
