MIIM - Bacteria and Fungi Causing Ocular Infections III - Week 3

Question 1

What 6 things about the ocular infections do you need to know?

Answer 1

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

Question 2

What 5 things about ocular pathogens do you need to know?

Answer 2

Ocular infections they can cause

Pathogenesis

Sources of the pathogens

Diagnosis

Management of infections

Question 3

What gram stain, shape, and metabolic type are haemophilus bacteria?

Answer 3

Gram negative pleomorphic rod (cocco-bacilli)

They are aerobic

Question 4

On what medium will haemophilus grow?

Answer 4

They are fastidious - they require enriched media like CHA (wont grow on HBA)

Question 5

Name the 7 kinds of typeable haemophilus strains, and the most common and serious disease-causing strain. Name 2 diseases that it can cause.

Answer 5

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.

Question 6

Describe non-typeable haemophilus influenzae, where it can be found, and 2 diseases it can cause.

Answer 6

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.

Question 7

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.

Answer 7

Mainly caused by haemophilus influenzae biogroup aegypticus.

Some strains cause virulent purpuric conjunctivitis and sepsis.

-Brazilian purpuric fever

Question 8

Name 4 means by which haemophilus causes diasease (pathogenesis).

Answer 8

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

Question 9

What specimen should be collected for a suspected haemophilus infection?

Answer 9

Discharge swab

Question 10

How can a suspected haemophilus swab be cultured in a lab, and what colour are the colonies (4)?

Answer 10

A culture of pus on enriched media (CHA), incubated in air + CO2, resulting in tiny colourless colonies.

Question 11

What two factors are required for a diagnostic laboratory confirmation of haemophilus culture?

Answer 11

X (haemin) and V (NAD) growth factors. Colonies cannot grow without these two factors. They are provided in lysed blood agar (CHA).

Question 12

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?

Answer 12

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.

Question 13

Where does haemophilus come from?

Answer 13

People, as endogenous and exogenous infections.

Question 14

Where in the human body does haemophilus influenzae colonise? Is this a problem?

Answer 14

The upper respiratory tract, usually asymptomatic.

Question 15

Name 2 ways haemophilus is spread from person to person.

Answer 15

By direct contact to the conjunctiva or through respiratory droplets (coughing/sneezing).

Question 16

How can haemophilus infections be prevented?

Answer 16

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).

Question 17

Where does the nasolacrimal duct drain to?

Answer 17

The inferior meatus and turbinate.

Question 18

What is dacryoadenitis?

Answer 18

Infection of the lacrimal sac, resulting in painful swelling in the outer region of the upper lid, with some degree of ptosis.

Question 19

Consider dacryoadenitis. Name two possible causes in children and one cause in adults.

Answer 19

Children - a complication of mumps or herpes simplex

Adults - associated with gonorrhoea (neisseria gonorrhoeae)

Question 20

How can dacryoadenitis be managed (3)?

Answer 20

Viral - rest and warm compresses

Other - specific appropriate treatment for the microbe

Question 21

Is dacryoadenitis common or rare?

Answer 21

Rare

Question 22

Is canaliculutis uni- or bilateral?

Answer 22

Unilateral

Question 23

Describe canaliculitis (6).

Answer 23

Chronic, recalcitrant, unilateral red eye, epiphora, and discharge.

Question 24

What do canaliculitis infections result in the formation of?

Answer 24

Concretions called dacryoliths that impede fluid drainage.

Question 25

What six bacteria can cause canaliculitis?

Answer 25

Actinomyces israelii Proionibacterium Strep spp. Staph spp. Candida albicans Pseudomonas aeruginosa

Question 26

What does canaliculitis look like?

Answer 26

Question 27

In what three ways can canaliculitis be managed?

Answer 27

Concretion removal, antibiotics, and possibly surgery

Question 28

Define epiphora. What does it look like?

Answer 28

Overflow of years and mucoid discharge

Question 29

What can stagnation of tears in a pathologically closed lacrimal srainage system result in?

Answer 29

Dacryoadenitis

Question 30

Which duct is obstructed in dacryocystitis?

Answer 30

The nasolacrimal duct

Question 31

Name 4 common symptoms of dacryocystitis. What does it look like?

Answer 31

Excess tears, pain, redness, swelling

Question 32

What can occur if an acute dacrycystitis infection spreads? What secondary condition can it cause?

Answer 32

Abcess formation requiring a drainage. A fistula may form spontaneously and cause orbital cellulitis.

Question 33

Name two types of dacryoadenitis.

Answer 33

Congenital - at birth, rare but potentially fatal Acquired - typically \>40 years, acute or chronic

Question 34

How can dscryoadenitis be managed (3)?

Answer 34

Oral antibiotics Analgesia Drainage

Question 35

Name 4 pathogens that can cause congenital dacryoadenitis and 4 for acquired.

Answer 35

Congenital - Staphylococcus aureus - Streptococcus pyogenes - Streptococcus pneumoniae - Haemophilusinfluenzae Acquired - Staphylococcus aureus - Streptococcus pyogenes - Streptococcus pneumoniae - Pseudomonas aeruginosa

Question 36

Describe what propionibacterium are, and how they have been reclassified for humans (for skin and oral microbiota).

Answer 36

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

Question 37

What gram stain, shape, and metabolic type are actinomyces, cutibacterium, and pseudopropionibacteria? do they produce spores?

Answer 37

They are all gram positive rods that produce no spores and are aerotolerant anaerobes.

Question 38

What does actinomyces israelii cause?

Answer 38

Actinomycosis - chronic suppurative abcesses

Question 39

What two bacteria are the leading cause of lacrimal canaliculitis?

Answer 39

Pseudopropionibacterium propionicum and Actinomyces israelii

Question 40

What three ocassional but serious cases of disease can cutibacterium acnes cause?

Answer 40

Post-surgical delayed endophthalmitis, prosthetic implant infection, and IOL lens infection

Question 41

Can cutibacterium acnes be cultured from conjunctivitis? Is this significant?

Answer 41

Yes it can, but not significant

Question 42

Where do Actinomyces, Cutibacterium and Pseudopropionibacterium come from?

Answer 42

People, as endogenous infections

Question 43

How can cutibacterium acnes cause acne?

Answer 43

It metabolises fatty acids around hair follicles on skin and is associated with acne in affected individuals

Question 44

Which of the following are part of the normal microbiota: Actinomyces Cutibacterium Pseudopropionibacterium

Answer 44

All three: Actinomyces - normal oral and nasal microbiota Cutibacterium - normal skin microbiota Pseudopropionibacterium - normal oral microbiota

Question 45

What is the pathogenesis of Actinomyces, Cutibacterium, and Pseudopropionibacterium (5)?

Answer 45

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)

Question 46

What specimen is collected for suspected Actinomyces, Cutibacterium, or Pseudopropionibacterium infection?

Answer 46

Discharge swab

Question 47

What gram stain, shape, and metabolic type are Actinomyces / Cutibacterium / Pseudopropionibacterium?

Answer 47

Gram positive rods, anaerobes.

Question 48

What kind of discharge is seen in an infection from Actinomyces / Cutibacterium / Pseudopropionibacterium?

Answer 48

Sulphur granules

Question 49

What laboratory findings would confirm an Actinomyces / Cutibacterium / Pseudopropionibacterium infection (2)?

Answer 49

Organisms from colonies producing propionic acid, and 16S rRNA.

Question 50

How long do Actinomyces / Cutibacterium / Pseudopropionibacterium take to grow, and on what media/incubation?

Answer 50

Slow growth (up to 7 days) on HBA anaerobically

Question 51

Describe how Actinomyces / Cutibacterium / Pseudopropionibacterium infections are managed (3) including antimicrobial susceptibility.

Answer 51

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.

Question 52

What is conjunctivitis, and is it serious?

Answer 52

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.

Question 53

Clinically, what three causes of conjunctivitis are hard to distinguish from one another?

Answer 53

Hard to distinguish bacterial from allergic or viral causes.

Question 54

How is acute conjunctivitis typically treated clinically? Does it involve laboratoy testing?

Answer 54

It is treated empirically (best guess therapy), based on observations and history, not lab findings.

Question 55

What two eyedrops can be used to empirically treat acute conjunctivitis? What three kinds of conjunctivitis cases require a different management?

Answer 55

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.

Question 56

Name 6 symptoms of conjunctivitis.

Answer 56

Redness of the sclera Increased tears Thick yellow, green, or white discharge Itchy/burning eyes Blurred vision Photosensitivity

Question 57

What is one way of differentiating a bacterial vs. viral cause for conjunctivitis?

Answer 57

Purulent discharge indicates bacterial, serous indicates viral.

Question 58

Does conjunctivitis typically spread to the other eye, or is it unilateral? Explain (3).

Answer 58

Can spread to the other eye. 1-2 days for bacteria, 2-3 days for viral.

Question 59

If discharge is present for a conjunctivitis case, is it still infectious or not?

Answer 59

Infectious while the discharge is present.

Question 60

Name 6 risk factors for conjunctivitis.

Answer 60

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)

Question 61

Name 4 ocular diseases and abnormalities that can increase risk of conjunctivitis.

Answer 61

Dry eye Blepharitis Ocular surface and eyelid abnormalities

Question 62

Name three ways to prevent conjunctivitis.

Answer 62

Good personal hygeine No towel sharing Exclude symptomatic people from childcare, pre-school, school, and work

Question 63

Name seven bacteria that can cause conjunctivitis. Which of these can cause neonatal conjunctivitis (2)?

Answer 63

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

Question 64

Describe Brazilian Purpuric Fever, whether it is serious, what it is preceded by, and what causes it.

Answer 64

It is a life threatening paediatric infection that is preceded by conjunctivitis, and is caused by Haemophilus influenzae aegypticus.

Question 65

Name 6 symptoms of Brazilian Purpuric Fever.

Answer 65

High fever Nausea Vomiting Severe abdominal pain Septic shock Death

Question 66

Which age group and individuals in what geographical area are most susceptible to Brazilian Purpuric Fever.

Answer 66

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.

Question 67

If conjuctivitis is found to be caused by haemophilus aegypticus, what is the preferred management, and what does it result in?

Answer 67

Prompt antibiotic treatment, preferrably with oral rifampin. It has been shown to prevent progression to Brazilian Purpuric Fever.