M: Bacteria causing ocular infections 3 - Week 3 Flashcards
What is the main virulence mechanism for strep. pneumoniae?
its polysaccharide capsule
Name and explain the 2 vaccines available for strep. pneumoniae (i.e. what do the vaccines contain)
- polysaccharide vaccine: contains 23 capsular polysaccharide antigens most commonly found in serious infection in adults
- Conjugate paediatric vaccines: contain the 7 or 13 most common capsular antigens assoc. with childhood pneumococcal infection
Describe the efficacy of the polysaccharide vaccine in adults vs children for strep. pneumoniae
adults: limited efficacy
children: poor efficacy (b/c the b cells haven’t matured yet)
What age group are typically given polysaccharide vaccine for strep. pneumoniae? How often?
people over 65 years who are at risk for their age group. Generally given every 5 years (b/c long term memory is not developed)
Where do streptococci come from?
People. Both endogenous and exogenous
What age group most commonly have S. pneumonia as part of their normal conjunctival flora?
children under 5yrs (around 13%)
What proportion of our population carry viridans strep in the oropharynx?
100%. All of us
What proportion of our population carry viridans strep in the conjuctiva/eyelids
2% of us
Name 6 typical microbes that can be involved with preseptal cellulitis
- staph aureus
- strep pneumoniae
- strep pyogenes
- haemophilus influenza type b (if unvacc)
- peptostreptococcus
- HSV 1 and 2, VSV
Describe the following features of Haemophilus:
- Gram stain and shape
- Growth requirements relating to O2
- Growth requirements in general
Haemophilus:
- gram negative, pleomorphic cocco-bacillus
- aerobe and capnophilic (CO2 loving)
- “fastidious” (requires enriched medium like chocolate agar to grow. Doesn’t grow on horse blood agar)
Which type of Haemophilus influenzae is the most pathological/most likely to cause problems?
Type B. Fortunately we vaccinate against it
What can infection with Haemophilus influenzae lead to? (4)
- preseptal cellulitis following lower respiratory tract infection and/or otitis media, acute conjuctivitis
What type of haemophilus influenzae is always a pathogen out of the following? Capsular or un-encapsulated
capsular
Where is un-encapsulated haemophilus found as part of normal flora?
nasaopharynx
T/F: un-encapsulated haemophilus influenzae can someimes cause acute conjunctivitis?
True
What is Haemophilus influenzae biovar aegypticus
is a primary pathogen causing acute conjunctivitis
- some strains cause a virulent purpuric conjunctivitis and sepsis (brazillian purpuric fever, BPF)
Where does haemophilus come from?
People. Endogenous and Exogenous
Where does haemophilus influenzae typically colonize. Does this result in symptoms?
colonises upper respiratory tract. (usually asymptomatic)
How can haemophilus be spread?
person to person by:
- direct contact (to the conjunctiva)
- or through respiratory droplets (cough and sneeze)
How does haemophilus spread through the body in infection?
spreads through the tissues, lead to cellulitis
Describe 4 features of Haemophilus that contribute to its pathogenesis (How does haemophilus cause disease)?
- primary pathogens have polysacch. capsule: hides PAMPs from immune recognition
- fimbrial adhesions: allow attachment to conjunctival and corneal surfaces
- lipo-oligosaccharide (LOS) in cell wall: activates inflammatory response and aids immune evasion (mimics “self”)
- produces and IgA protease
Describe the laboratory diagnosis of Haemophilus.
Specimen:
Microscopy:
Culture:
Specimen: discharge (swab)
Microscopy: Gram negative pleomorphic rods (cocci-bacillus)
Culture: culture of pus on enriched media (choc agar, incubated in air and CO2) lead to tiny colourless colonies
Describe the laboratory diagnosis of Haemophilus
Confirmation:
Confirmation: organisms have specific requirements for “X” (haemin) and “V” (NAD) growth factors
– haemophilus needs BOTH for it to grow
(these growth factors can be found in lysed blood agar e.g. chocolate agar)
How do you manage Haemophilus?
- haemophilus may require resistance to commonly used antimicrobials (such as penicilin G and chloramphenicol): need to TEST ANTIMICROBIAL SUSCEPTIBILITY to ensure targeted therapy
- for orbital cellulitis use IV antimicrobials: 3rd generation cephalosporins (e.g.cefotaxime)
How do you prevent Haemophilus?
Vaccination with Hib vaccine (however infection with types other than type b still occur)
Define Dacryocystitis
Infection of the lacrimal sac/duct, usually associated with obstruction, leading to a stasis of lacrimal sac contents
List the symptoms for dacryocystitis
- excess tears
- pain
- redness
- swelling
What can an acute dacryocystitis infection lead to?
abscess formation requiring drainage
How common and severe is congenital dacryocystitis?
rare but potentially serious
Describe the 2 types of dacryocystitis:
- congenital - rare, potentially fatal
- acquired - can be acute or chronic
What 2 bacteria cause acute dacryocystitis?
S. aureus, Strep. pyogenes
What 2 bacteria might cause acquired dacryocystitis?
proprionibacterium acnes or actinomyces israeli
In what age group does acquired dacryocystitis commonly occur in?
over 40yrs old
How do you manage dacryocystitis?
oral antibiotics and analgesia (pain relief), drainage (?)
Can dacryocystitis lead to orbital cellulitis?
yes
Define Canaliculitis
inflammation of the lacrimal (tear) duct
How common is canaliculitis? What age group does it affect?
relatively rare, affects adults over 50yrs
What type of conditions does canaliculitis present with? (3)
chronic, recalcitrant unilateral red eye, epiphora, and discharged
Explain how canaliculus infection leads to impaired fluid drainage
through the formation of concretions (dacryoliths)
Name the 2 most common bacterial causes for canaliculitis
- Actinomyces israelii
- Proprionibacterium proprionicum
How do you manage canaliculitis? (2-3)
- remove concretions
- antibiotics
- surgery (?)
Define Epiphora
overflow of tears (and mucoid discharge) onto the face
Define Dacryoadenitis
inflammation of the lacrimal gland
What symptoms present with dacryoadenitis?
painful swelling in outer region of upper lid, with some degree of ptosis (eyelid drooping)
How common is dacryoadenitis? Where is it seen? (i.e. who)
rare - most often seen in children as a complication of viral infections (e.g. mumps) or in adults in association with gonorrhoea
How do you manage dacryoadenitis?
- if viral: rest and warm compress
- if other cause: specific appropriate treatment
Describe the following features of actinomyces/cutibacterium
- gram stain and appearance in microscopy
- oxygen requirements
- both are gram positive rods
- both do not produce spores and are aerotolerant anaerobes (require an anaerobic environment, but can tolerate O2)
(however, while they can survive with O2, they need anaerobic environment to actually grow)
Describe the outcomes of the following pathogens in ocular infection:
- actinomyces israelii
- pseudopropionibacterium propionicus
actinomyces israelii - causes actinomycosis; chronic, suppurative abscesses
pseudopropionibacterium propionicus and actinomyces israeli – leading cause of lacrimal canaliculitis
Describe the outcomes of the following pathogens in ocular infection:
- cutibacterium acnes
cutibacterium acnes – occasional cause of post-surgical delayed endophthalmitis; infection of prosthetic implants and IOLs; lacrimal sac obstruction, keratitis
Where do actinomyces and pseudopropionibacteria and cutibacterium come from?
people, as endogenous infections
Where do you generally find cutibacterium acnes
common member of skin and ocular microbiota (in and around hair follicles): metabolises fatty acids in these sites
Where do you generally find psuedoproprionibacterium?
normal oral microbiota
Where do you generally find actinomyces israelii?
part of normal oral and nasal microbiota
Describe 3 features/abilities of actinomyces/psueoprop…/cutibacterium that contribute to their ability to cause disease.
- cell wall constituents = protease resistant (therefore not degraded by neutrophils and macrophages. Lead to chronic infection)
- can suppress T cell activation (chronic infl.)
- have selective growth advantage (lipid metabolism, bacteriocin production)
What is bacteriocin?
toxin produced to inhibit growth of other bacteria
Describe the laboratory diagnosis of actinomyces/propionibacterium.
Specimen:
Microscopy:
Culture:
Specimen = discharge
Microscopy = gram positive rods (may appear branching)
Culture = culture of pus and granules under anaerobic conditions. Slow growing
Describe the laboratory diagnosis of actinomyces/propionibacterium in terms of
Confirmation:
Confirmation = organisms from colonies of this produce propionic acid
How long might it take actinomyces/propionibacterium to grow on anaerobically incubated horse blood agar?
up to 7 days
How do you manage actinomyces/pseudopr…/cutibacterium infection?
- susceptible to most common antimicrobials
- however antimicrobial therapy alone will not suffice
- site of infection will need SURGICAL REMOVAL OF CONCRETIONS and debris to achieve a cure
Define conjunctivitis
inflammation of conjunctiva (outermost membrane of the eye) and inner surface of eyelid
How would you describe the infectious-ness of bacterial/viral conjunctivitis?
very infectious
In what age group can conjunctivitis infection be sight-threatening?
newborns
List 6 symptoms of conjunctivitis
- redness in white/corner of eye
- increased amount of tears
- thick yellow, green or white discharge
- itchy/burning eyes
- blurred vision
- increased sensitivity to light (if significant, refer to ophthalmologist)
How long is the typical incubation period for conjunctivitis?
24 to 72 hours
List 6 risk factors for conjunctivitis
- poor personal/CL hygeine
- contaminated cosmetics/chronic use of topical medications
- crowed living/social conditions
- ocular diseases incl. dry eye, blepharitis, and anatomic abnormalities of ocular surface and lids
- recent ocular surgery
- immune compromise
List 3 ways you can prevent conjunctivitis
- good personal hygeine (hand washing)
- do not share towels, face cloths or lenses
- exclude symptomatic people from childcare, school or work
Is bacterial conjunctivitis easy or hard to distinguish from allergic or viral causes?
Hard to distinguish
How do you treat acute conjunctivitis? (in terms of the ideology)
is treated empirically (“best guess” therapy) based on observations and history (NOT laboratory findings_
Describe the management of conjunctivitis
for suspected bacterial infections: framycetin eye drops or chloramphenicol eye drops (can use “delayed prescription” approach)
Infections that fail to respond, chronic infections, and neonatal infections: MUST be investigated with prompt referral to ophthalmologist
List 4-5 possible bacterial pathogens for bacterial conjunctivitis
staph. aureus, strep. pyogenes, strep. pneumoniae, haemophilus influenzae, moraxella
List the 2 main bacterial pathogens associated with neonatal conjunctivitis
- neisseria gonorrhoeae
- chlamydia trachomatis
What is Brazilian Purpuric Fever?
a life threatening paediatric infection prceeded by conjunctivitis caused by a specific strain of haemophilus influenzae biogroup aegyptius
What age group are most susceptible to Brazillian Purpuric Fever?
children under 5
What is the best management option for brazillian purpuric fever?
If conjunctivitis is found to be caused by haemohilus aegyptius biogroup III, follow with prompt antibiotic treatment: preferably with oral rifampin
