MIIM - Bacteria and Fungi Causing Ocular Infections III - Week 3 Flashcards
What 6 things about the ocular infections do you need to know?
Characteristics of the disease - symptoms, distinguishing features, outcomes, consequences
Causative pathogens
Sources of causative pathogens
Pathogenesis - how they cause disease, and major virulence factors
Diagnosis - samples to collect, what tests are done to identify the cause
Management of the disease - treatment and prevention
What 5 things about ocular pathogens do you need to know?
Ocular infections they can cause
Pathogenesis
Sources of the pathogens
Diagnosis
Management of infections
What gram stain, shape, and metabolic type are haemophilus bacteria?
Gram negative pleomorphic rod (cocco-bacilli)
They are aerobic
On what medium will haemophilus grow?
They are fastidious - they require enriched media like CHA (wont grow on HBA)
Name the 7 kinds of typeable haemophilus strains, and the most common and serious disease-causing strain. Name 2 diseases that it can cause.
Haemophilus influenzae type a, b, c, d, e, and f.
Type b is the most common and serious strain.
It causes preseptal cellulitis following lower respiratory tract infection, and/or otitis media, and acute conjunctivitis.
Describe non-typeable haemophilus influenzae, where it can be found, and 2 diseases it can cause.
It is unencapsulated (thus untypeable), and is found in the normal microbiota of the nasopharyx.
It can cause acute conjunctivitis and opportunistic infections like endophthalmitis.
What is the primary pathogen causing acute conjunctivitis? Name two additional diseases/symptoms that some strains can cause, as well as what this is classed as.
Mainly caused by haemophilus influenzae biogroup aegypticus.
Some strains cause virulent purpuric conjunctivitis and sepsis.
-Brazilian purpuric fever
Name 4 means by which haemophilus causes diasease (pathogenesis).
It has a polysaccharide (classed a-f) which hides PAMPs from immune recognition
Fimbrial adhesins allow attachment to conjunctival and corneal surfaces
Lipo-oligosaccharides in the cell wall activates an inflammatory response, aiding immune evasion by mimicking ‘self’
Produces IgA proteases
What specimen should be collected for a suspected haemophilus infection?
Discharge swab
How can a suspected haemophilus swab be cultured in a lab, and what colour are the colonies (4)?
A culture of pus on enriched media (CHA), incubated in air + CO2, resulting in tiny colourless colonies.
What two factors are required for a diagnostic laboratory confirmation of haemophilus culture?
X (haemin) and V (NAD) growth factors. Colonies cannot grow without these two factors. They are provided in lysed blood agar (CHA).
How can haemophilus be managed? What is its susceptibility to antimicrobials like penicillin G? What should be done in this case? What is the ideal therapy for orbital cellulitis?
Haemophilus may acquire resistance to common antimicrobials like penicillin G. Antimicrobial susceptibility must be tested to ensure targeted therapy.
IV antimicrobials is ideal for orbital cellulitis.
Where does haemophilus come from?
People, as endogenous and exogenous infections.
Where in the human body does haemophilus influenzae colonise? Is this a problem?
The upper respiratory tract, usually asymptomatic.
Name 2 ways haemophilus is spread from person to person.
By direct contact to the conjunctiva or through respiratory droplets (coughing/sneezing).
How can haemophilus infections be prevented?
There is a vaccine for type b. Infections involving the other strains, as well as non-typeable strains still occur however (on top of children who arent vaccinated for type b).
Where does the nasolacrimal duct drain to?
The inferior meatus and turbinate.
What is dacryoadenitis?
Infection of the lacrimal sac, resulting in painful swelling in the outer region of the upper lid, with some degree of ptosis.
Consider dacryoadenitis. Name two possible causes in children and one cause in adults.
Children - a complication of mumps or herpes simplex
Adults - associated with gonorrhoea (neisseria gonorrhoeae)
How can dacryoadenitis be managed (3)?
Viral - rest and warm compresses
Other - specific appropriate treatment for the microbe
Is dacryoadenitis common or rare?
Rare
Is canaliculutis uni- or bilateral?
Unilateral
Describe canaliculitis (6).
Chronic, recalcitrant, unilateral red eye, epiphora, and discharge.
What do canaliculitis infections result in the formation of?
Concretions called dacryoliths that impede fluid drainage.
What six bacteria can cause canaliculitis?
Actinomyces israelii
Proionibacterium
Strep spp.
Staph spp.
Candida albicans
Pseudomonas aeruginosa
What does canaliculitis look like?
In what three ways can canaliculitis be managed?
Concretion removal, antibiotics, and possibly surgery
Define epiphora. What does it look like?
Overflow of years and mucoid discharge
What can stagnation of tears in a pathologically closed lacrimal srainage system result in?
Dacryoadenitis
Which duct is obstructed in dacryocystitis?
The nasolacrimal duct
Name 4 common symptoms of dacryocystitis. What does it look like?
Excess tears, pain, redness, swelling
What can occur if an acute dacrycystitis infection spreads? What secondary condition can it cause?
Abcess formation requiring a drainage. A fistula may form spontaneously and cause orbital cellulitis.
Name two types of dacryoadenitis.
Congenital - at birth, rare but potentially fatal
Acquired - typically >40 years, acute or chronic
How can dscryoadenitis be managed (3)?
Oral antibiotics
Analgesia
Drainage
Name 4 pathogens that can cause congenital dacryoadenitis and 4 for acquired.
Congenital
- Staphylococcus aureus
- Streptococcus pyogenes
- Streptococcus pneumoniae
- Haemophilusinfluenzae
Acquired
- Staphylococcus aureus
- Streptococcus pyogenes
- Streptococcus pneumoniae
- Pseudomonas aeruginosa
Describe what propionibacterium are, and how they have been reclassified for humans (for skin and oral microbiota).
They are bacteria that produce propionic acid as an end product of fermentation, including dairy milk and human skin microbiota.
Human skin species is now in the genus cutibacterium
Oral species is now in the genus pseudopropionibacterium
What gram stain, shape, and metabolic type are actinomyces, cutibacterium, and pseudopropionibacteria?
do they produce spores?
They are all gram positive rods that produce no spores and are aerotolerant anaerobes.
What does actinomyces israelii cause?
Actinomycosis - chronic suppurative abcesses
What two bacteria are the leading cause of lacrimal canaliculitis?
Pseudopropionibacterium propionicum and Actinomyces israelii
What three ocassional but serious cases of disease can cutibacterium acnes cause?
Post-surgical delayed endophthalmitis, prosthetic implant infection, and IOL lens infection
Can cutibacterium acnes be cultured from conjunctivitis? Is this significant?
Yes it can, but not significant
Where do Actinomyces, Cutibacterium and Pseudopropionibacterium come from?
People, as endogenous infections
How can cutibacterium acnes cause acne?
It metabolises fatty acids around hair follicles on skin and is associated with acne in affected individuals
Which of the following are part of the normal microbiota:
Actinomyces
Cutibacterium
Pseudopropionibacterium
All three:
Actinomyces - normal oral and nasal microbiota
Cutibacterium - normal skin microbiota
Pseudopropionibacterium - normal oral microbiota
What is the pathogenesis of Actinomyces, Cutibacterium, and Pseudopropionibacterium (5)?
Adhesins/fimbriae for adhesion to tissue/biofilms
Stimulates innate immunity causing pus
Grows in colonies/biofilms made of cohesive branching filaments of cells, resisting phagocytosis
Selective growth advantage (lipid metabolism, bacteriocin production inhibitng other bacteria)
Tissue degrading enzymes (haemolysin, lipases, proteases)
What specimen is collected for suspected Actinomyces, Cutibacterium, or Pseudopropionibacterium infection?
Discharge swab
What gram stain, shape, and metabolic type are Actinomyces / Cutibacterium / Pseudopropionibacterium?
Gram positive rods, anaerobes.
What kind of discharge is seen in an infection from Actinomyces / Cutibacterium / Pseudopropionibacterium?
Sulphur granules
What laboratory findings would confirm an Actinomyces / Cutibacterium / Pseudopropionibacterium infection (2)?
Organisms from colonies producing propionic acid, and 16S rRNA.
How long do Actinomyces / Cutibacterium / Pseudopropionibacterium take to grow, and on what media/incubation?
Slow growth (up to 7 days) on HBA anaerobically
Describe how Actinomyces / Cutibacterium / Pseudopropionibacterium infections are managed (3) including antimicrobial susceptibility.
Susceptible to most commonly used antimicrobials - resistance is emerging.
In many cases, concretions and debris need to be surgically removed from the sites of injection.
Duct integrity may need to be restored such as a stent insertion or a new fistula connecting the lacrimal sac to the nasopharynx.
What is conjunctivitis, and is it serious?
It is the inflammation of the conjunctiva and the inner surfaces of the eyelid. Not a serious health risk if diagnosed promptly, but infections in newborn can be sight-threatening.
Clinically, what three causes of conjunctivitis are hard to distinguish from one another?
Hard to distinguish bacterial from allergic or viral causes.
How is acute conjunctivitis typically treated clinically? Does it involve laboratoy testing?
It is treated empirically (best guess therapy), based on observations and history, not lab findings.
What two eyedrops can be used to empirically treat acute conjunctivitis? What three kinds of conjunctivitis cases require a different management?
Framycetin
Chloramphenicol
Infections that fail to respond to these drugs, chronic conjunctivitis, and neonatal infections must be investigated further, including an ophthalmologist referral, and a lab examination of pus for a specific treatment.
Name 6 symptoms of conjunctivitis.
Redness of the sclera
Increased tears
Thick yellow, green, or white discharge
Itchy/burning eyes
Blurred vision
Photosensitivity
What is one way of differentiating a bacterial vs. viral cause for conjunctivitis?
Purulent discharge indicates bacterial, serous indicates viral.
Does conjunctivitis typically spread to the other eye, or is it unilateral? Explain (3).
Can spread to the other eye.
1-2 days for bacteria, 2-3 days for viral.
If discharge is present for a conjunctivitis case, is it still infectious or not?
Infectious while the discharge is present.
Name 6 risk factors for conjunctivitis.
Poor personal hygeine (including CL care)
Contaminated cosmetics
Chronic use of topical medications
Crowded living
Recent ocular surgery (exposed suture/ocular foreign bodies)
Compromised immunity (especially neonates)
Name 4 ocular diseases and abnormalities that can increase risk of conjunctivitis.
Dry eye
Blepharitis
Ocular surface and eyelid abnormalities
Name three ways to prevent conjunctivitis.
Good personal hygeine
No towel sharing
Exclude symptomatic people from childcare, pre-school, school, and work
Name seven bacteria that can cause conjunctivitis. Which of these can cause neonatal conjunctivitis (2)?
Staphylococcus aureus
Streptococcus pyogenes
Streptococcus pneumoniae
Haemophilus influenzae (including aegypticus)
Moraxella spp.
Neisseria gonorrhoeae
Chlamydia trachomatis
Neisseria gonorrhoeae and Chlamydia trachomatis can cause neonatal conjunctivitis
Describe Brazilian Purpuric Fever, whether it is serious, what it is preceded by, and what causes it.
It is a life threatening paediatric infection that is preceded by conjunctivitis, and is caused by Haemophilus influenzae aegypticus.
Name 6 symptoms of Brazilian Purpuric Fever.
High fever
Nausea
Vomiting
Severe abdominal pain
Septic shock
Death
Which age group and individuals in what geographical area are most susceptible to Brazilian Purpuric Fever.
Children under 5 are most susceptible because they lack serum bactericidal activity. Older children and adults have much higher titres, which is protective.
Children residing in warmer geographical areas have been associated with a higher risk.
If conjuctivitis is found to be caused by haemophilus aegypticus, what is the preferred management, and what does it result in?
Prompt antibiotic treatment, preferrably with oral rifampin. It has been shown to prevent progression to Brazilian Purpuric Fever.
