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
