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