MIIM - Bacteria and Fungi Causing Ocular Infections IV - Week 3 Flashcards
What gram stain, shape, and metabolic state is moraxella?
Gram negative diplococci
Strict aerobe
Is moraxella oxidase and catalase positive or negative?
Positive for both
Name the two major moraxella pathogens, and two conditions each they can cause.
Moraxella lacunata
- conjunctivitis
- keratitis
Moraxella catarrhalis
- acute conjunctivitis
- opportunistic infection (like endophthalmitis)
Name 2 means of pathogenesis for moraxella.
Fimbriae mediate attachment
Lipopolysaccharides in the cell wall induces inflammation
Name a source for each of the two major moraxella bacteria.
Moraxella catarrhalis - normal component of respiratory and ocular flora
Moraxella lacunata - also found as a commensal
What is the ideal specimen for a suspected case of moraxella?
Discharge swab
What antibiotics is moraxella resistant to (explain why), and what is the management for an infection?
Most isolates produce β-lactamase, and is resistant to penecillin and amoxycillin.
Amoxycillin-clavulanate or oral cephalosporins are used.
Susceptibility test beforehand is ideal.
What gram stain, shape, and metabolic state are neisseria bacteria?
Gram negative diplococci
Aerobic
Name the two major neisseria bacteria, and the systemic diseases they cause (3).
Neisseria meningitidis - meningiococcal disease
-meningitis and septicaemia
Neisseria gonnorhoeae - gonorrhoea
How is gonorrhoea transmitted?
Sexually
Are neisseria bacteria able to survive easily outside the body or are they fastidious?
They are fastidious
Name two ocular diseases caused by neisseria gonorrhoea.
Adult conjunctivitis
Ophthalmia neonatorum
What can prolonged untreated conjunctivitis lead to?
Keratitis
Name 4 ways ophthalmia neonatorum can be prevented.
Screening pregnant women from high risk populations
-antibiotic treatment for those infected
Prophylactic treatment of newborns with ophthalmic ointments like tetracyclines or erythromycin - raises resistance concerns
Silver nitrate eye drops used at birth to prevent gonococcal eye infection
Name one way chemical conjunctivitis can be induced?
Siver nitrate drops to prevent gonococcal eye infection
Name 6 means of pathogenesis in neisseria.
- Able to penetrate the corneal epithelium without pre-existing defects
- Fimbriae attachement
- Variation in fimbrial proteins to counteract immune response
- Outer membrane proteins mediate invasion and survival in phagocytes
- Cell wall components, especially lipo-oligosaccharides, cause inflammation
- IgA protease
Name a source of neisseria. Is it a part of the normal microbiota?
It spreads from contacts with gonorrhoea (sexually or poor hygiene).
It is not part of the normal microbiota.
What two ideal specimen for a neisseria lab diagnosis? Elaborate.
A conunctival swab or corneal scraping. Must be transported quickly to the lab in an appropriate transport medium as it is fastidious.
Is neisseria pyogenic?
Yes
How can neisseria be cultured?
Using a culture of pus or scrapings on enriched media.
Antibiotics may sometimes be added to surpress the normal microbiota.
Is neisseria oxidase positive?
Yes
Name 4 ways neisseria infections can be managed.
- Penicillin course
- Resistance is common in urban areas - susceptibility tests are essential
- Empirical treatment depends on source of infection
- Treating associated STI essential
Name three ways neisseria infections can be prevented.
Health education
Good hygiene
Effective diagnosis and treatment
What bacteria is responsible for the most common STI?
Chlamydia trachomatis
Does chlamydia trachomatis have a lipopolysaccharide membrane and peptidoglycan layer?
Has an outer lipopolysaccharide layer, but no peptidoglycan
Describe the gram stain of chalmydia trachomatis. Elaborate on what is seen on a slide.
Technically it is gram negative, but is not seen in a stain, because of its size.
Briefly describe the life cycle of chlamydiae (7).
- Elementary bodies attach by adhesins into mucosal epithelia.
- EBs are endocytosed into inclusion, and doesnt fuse with a lysosome.
- EBs transform into metabolically active reticulate bodies.
- In cells with multiple inclusions, they fuse to form one.
- Reticulate bodies multiply.
- Reticulate bodies mature back into infectious EBs or persist in the cell as an aberrant body.
- Newly matured EBs are released to infect other cells.
What two diseases can chlamydia trachomatis cause, and what serovars?
Serovars A-C - trachoma
Serovars D-K - inclusion conjunctivitis
What chlamydia bacteria is associated with follicular conjunctivitis?
Chlamydophila psittaci - causes psittacosis, associated with follicular conjunctivitis
What is the most common cause of preventable blindness worldwide?
Trachoma
What conditions is trachoma most common in (5)?
Hot Dry Dusty Scarce water Poor sanitation
Describe the progression of trachoma blindness beginning with repeated infection of the conjunctiva (9).
- Repeated infection of the conjunctiva
- Lymphoid follicles and inflammatory infiltration
- Eyelid scarring
- Trichiasis
- Entropion
- Corneal abrasion
- Scarring
- Blindness
Name three structures that are damaged with trichoma progression.
Goblet cell, lacrimal gland, and tear duct destruction.
What lid defect does trachoma cause?
Defects in lid closure like trachiasis.
Describe trachiasis.
Eyelashes are misdirected, and grow inwards towards the eye, rubbing on the cornea, conjunctiva, and inner lid surface, causing irritation.
Describe entropion. Which eyelid does it usually affect, and which one is affected in trachoma?
It is the turning in of the edge of an eyelid, usually seen on the lower eyelid, but both are affected in trachoma. It causes the lashes and lid edge to rub against the eye.
Briefly describe the lifecycle of chlamydiae (3).
Flies carry the bacteria onto eyes when feeding on discharge.
Bacteria infects and spreads through direct contact.
Flies breeding in human faeces spread the disease to others.
Briefly describe how trachoma causes blindness (3).
The infection inflames and thickens the upper eyelid.
The scarred eyelids turn inwards and rubs against the cornea.
The lashes scratching the cornea continually leads to blindness.
Name four symptoms of inclusion conjunctivitis in adults.
Scanty mucopurulent discharge
Epithelial keratitis
Marginal and central infiltrates
Does corneal scarring and neovascularisation occur in inclusion conjunctivitis?
Yes
Does inclusion conjunctivitis involve one or both eyes?
In adults, usually just one eye.
What appearance does the lower eyelid have with inclusion conjunctivitis, and what are these structures?
The eyes are red, and the lower eyelid has many small red bumps, which are lymphoid follicles.
This is called collicular conjunctivitis.
In most cases, how does adult inclusion conjunctivitis spread? Name three additional ways.
Mostly caused due to the eye being exposed to infected genital secretions ( ͡° ͜ʖ ͡°) Water in swimming pools Contaminated hot tubs Sharing makeup
Name 4 symptoms of neonatal inclusion conjunctivitis.
Eyelid oedema
Hyperaemia
Conjunctival infiltration
Discharge
If untreated, what does neonatal inclusion conjunctivitis lead to?
Blenorrhoea, which is excess mucus
In what population of babies is neonatal inclusion conjunctivitis seen in?
Babies born vaginally to an asymptomatic (but infected) mother
When does neonatal inclusion conjunctivitis present afterbirth?
5-19 days afterbirth
Name three means of pathogenesis in chlamydiae.
Adhesins allowing colonisation of columnar epithelium
Evasion of host immune responses by forming inclusions
Inhibits apoptosis
Define tropism.
Specificity towards a particular tissue
What two specimens are ideal for a suspected chlamydia infection for lab diagnosis?
Conjunctival discharge or corneal scraping.
What is seen on a gram stain of chlamydia (4)?
Lymphocytes
Monocytes
Macrophages
Chlamydiais not seen
What is seen on a giemsa stain of chlamydia?
Intracytoplasmic inclusions
Name 2 detection methods for chlamydia.
Antigen detection by enzyme immunoassay - EIA
Nucleic acid detection by PCR
Name 3 means of management for chlamydia infection.
Long term antibiotic treatment due to antibiotics.
Personal hygiene
Contact tracing of STI
What syndrome is C. trachomatis serovars D-K infection associated with?
Reiter’s syndrome
What is syphilis caused by?
The spirochaete - treponema pallidum
When left untreated, name the three stages of syphilis.
Primary - painless chancre at the inoculation site
Secondary - skin rashes, other organ involvement including ocular complications
Tertiary - cardiovascular involvement and neurosyphilis
Describe a chancre.
Fluid filled ulcer
How can a definitive diagnosis for syphilis be made?
Lab diagnosis via a serology for antibody response.
What percentage of those with syphilis will usually have ocular complications, and what is the most common complication?
10%, most commonly being uveitis.
Which antibiotic is used to treat syphilis? Is resistance a problem?
Penicillin is used, which it typically doesnt resist. Reinfection can occur.
Name 5 ocular conditions that can be caused by syphilis.
Keratitis Keratoconjunctivitis Orbital cellulitis Endophthalmitis Uveitis
Describe keratitis.
Inflammation of the cornea.
Describe two causes of non-infectious keratitis.
Minor injury or wearing contact lenses too long.
Is infectious keratitis an emergency?
Yes, urgent referral is essential.
List 7 symptoms keratitis.
Red eye Eye discomfort Photophobia Blurred or decreased vision Pain Vision loss Pus
Name three risk factors of keratitis associated with contact lens wear.
Wearing them too long
Poor disinfection
Wearing them while swimming
List 4 risk factors for keratitis (aside from those associated with contact lenses).
Reduced immunity (including corticosteroid use)
Warm climate
Previous eye injury
Recent corneal disease
Name 5 bacteria that can cause keratitis.
Staphylococcus aureus Streptococcus pneumoniae Pseudomonas aureginosa Enterobacteriaceae Moraxella
Name three non-bacterial agents that can cause keratitis.
Fungi
Parasites (like acanthomoeba)
Viruses
