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OD2 (S1&2) > MIIM - Bacteria and Fungi Causing Ocular Infections V - Week 3 > Flashcards

MIIM - Bacteria and Fungi Causing Ocular Infections V - Week 3 Flashcards

1
Q

Describe the gram stain, shape, and metabolic state of pseudomonas. Does it produce spores? What are its growth requirements?

A

It is a gram negative rod
Aerobic
Minimal growth requirements

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2
Q

What two pigments are produced by pseudomonas?

A

Pyocyanin
Fluorescein

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3
Q

What bacteria is the most common cause of contact lens associated keratitis.

A

Pseudomonas aureginosa

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4
Q

Following eye injury, what bacteria is a common cause of exogenous endophthalmitis?

A

Pseudomonas aureginosa

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5
Q

Are the outcomes of pseudomonas eye infections good or poor?

A

Poor

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6
Q

Name 7 means of pathogenesis for pseudomonas.

A

Adhesion structures, especially good for CL, CL cases
Nutritionally resourceful - ubiquitous
Opportunistic
Induces inflammatory response
Produces exotoxins
Pyocyanin targets many pathways
Has cytotoxic and invasive strains

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7
Q

Name 4 places where pseudomonas could form a biofilm.

A

CL, CL cases, pipes, and showerheads

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8
Q

Name two specimens that can be used in a suspected pseudomonas infection.

A

Conjunctival swab
Corneal scraping

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9
Q

What do cultures of pseudomonas look and smell like?

A

Large colonies which produce blue-green water soluble pigment
Has a distinct sweet ammonia smell

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10
Q

Is pseudomonas oxidase positive or negative?

A

Positive

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11
Q

What media does pseudomonas grow on?

A

Basal media like NA

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12
Q

Is pseudomonas aureginosa inherently resistant or susceptible to most antibiotics?

A

Is resistant to many commonly used antibiotics, and can acquire resistance to others.

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13
Q

What should be done prior to treating pseudomonas with antibiotics?

A

Susceptibility test

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14
Q

Name 4 ways pseudomonas infections can be prevented.

A

Preventing CL associated infections by improving cleaning and wearing compliance
Discourage home-made cleaning salines
Using approved and sterile cleansers to remove biofilms
Using sterile CL storage solutions

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15
Q

Name 5 ocular diseases that can be caused by pseudomonas.

A

Keratitis
Keratoconjunctivitis
Orbital cellulitis
Endophthalmitis
Uveitis

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16
Q

How can orbital cellulitis cause a thrombosis, and is this serious?

A

If the infection spreads through thin bone, the abcess can pass into the blood stream.
Is life threatening.

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17
Q

Does orbital cellulitis cause proptosis?

A

It may

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18
Q

Name 4 agents that can cause orbital cellulitis.

A

Streptococcus pneumoneae
Haemophilus influenzae type b
Staphylococcus aureus
Streptococcus pyogenes

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19
Q

What is the most common cause of orbital cellulitis?

A

Sinus infection

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20
Q

Define endophthalmitis.

A

Inflammation of the interior of the eye (inside the globe).

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21
Q

What is the typical cause of endophthalmitis?

A

Eye surgery or trauma

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22
Q

Is endophthalmitis a minor condition or an emergency?

A

Emergency

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23
Q

Name 5 symptoms of endophthalmitis.

A

Progressive vision loss, photophobia, eye pain, red/pink eye, floaters

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24
Q

Name an endogenous source of endophthalmitis. Are these cases common or rare?

A

Haematogenous spread from a distant source like endocarditis.
These are rare.

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25
Q

Name 3 ways of managing an edophthalmitis infection.

A

Intravitreal injection of antibiotics - repeated if no response
-systemic antibiotics should be used if the source is endogenous
Vitrectomy in severe cases

26
Q

Can vision be retained or restored in endophthalmitis cases?

A

If appropriate care is given, useful vision can be recovered. In severe cases, it may result in the loss of sight or the eye.

27
Q

Describe the gram stain, shape and metabolic type of bacillus bacteria. Do they produce spores? Where are they found?

A

They are large gram positive rods
Produce spores
Aerobic or facultative anaerobes
Found in soil and dust

28
Q

Are bacillus bacteria easily cultured in labs?

A

Yes

29
Q

What is bacillus cereus, and what disease is it commonly associated with?

A

A opportunistic pathogen associated with exogenous endophthalmitis

30
Q

What is the gram stain, shape, and metabolic type of clostridia? Do they produce spores?

A

Large gram positive rods
Produce spores
Obligate anaerobes

31
Q

Where are clostridia found (3)?

A

Soil, dust, and the GIT of warm-blooded animals (including humans)

32
Q

What two diseases can clostridia cause?

A

Keratitis and exogenous endophthalmitis

33
Q

Name three species of clostridia, and a disease associated with each.

A

C. tetani - tetanus
C. botulinum - botulism
C. perfringens - gas gangrene/food poisoning

34
Q

Describe the gram stain ,shape, and metabolic type of enterobacteriaceae.

A

Gram negative rods
Facultative anaerobes

35
Q

Name 4 enterobacteriaceae associated with ocular disease. Describe which are normal microbiota, and which arent.

A

Environmental (associated with water)
-Serratia

Normal microbiota
-Proteus
-E. coli
-Klebsiella

36
Q

In what two ways are enterobacteriaceae associated with ocular disease?

A

Contact lens associated infections
Penetrating eye injuries

37
Q

Are enterobacteriaceae resistant or susceptible to antimicrobials?

A

Can be very resistant

38
Q

How can enterobacteriaceae infections be managed (1) and prevented (1)?

A

Due to resistance, antibiotic susceptibity testing is essential
Prevention of CL infections by improving wearing and cleaning compliance

39
Q

What kind of stain, metabolic type, and shape are mycobacteria?

A

Acid fast stain needed
Large rods
Aerobic

40
Q

Name the two major mycobacteria, and the disease they cause.

A

M. tuberculosis - tuberculosis
M. leprae - leprosy

41
Q

Do mycobacteria grow fast or slowly? Describe why.

A

Slow growing due to restricted entry of nutrients through its waxy cell wall

42
Q

Do tuberculosis or leprosy infect the eye as part of a systemic infection?

A

Yes

43
Q

Name two mycobacteria species that cause keratitis? What other disease can they cause?

A

M. chelonae
M. fortuitum
They can also cause endophthalmitis

44
Q

What disease can mycobacteria rarely cause?

A

Scleritis

45
Q

Name two means of managing mycobacteria infection.

A

Susceptibility testing for antibiotics
Surgery for patients who dont respond

46
Q

What kind of sterol can be found in the cell membrane of fungi?

A

Ergosterol

47
Q

In what two ways do fungi propagate?

A

Vegetatively or by spores

48
Q

What are the two classifications of fungi (3)?

A

Yeast - unicellular
Moulds - filamentous
Some can be both - dimorphic

49
Q

Define saprophytic.

A

Gain energy from the breakdown of dead organic matter

50
Q

Can fungi infect eyes with an intact epithelium?

A

Rarely - they are opportunistic

51
Q

Are fungal eye infections common? What is the most common disease?

A

They are rare.
Keratitis is the most common

52
Q

How do fungi cause corneal damage?

A

Injury by tree branches

53
Q

What fungal infection do CL wear predispose one to?

A

Oculomycoses

54
Q

What fungi is involved with causing fungal endophthalmitis in hospitalised patients?

A

Candida sp.

55
Q

Name 4 common fungi for ocular infections and their classification.

A

Yeast
-Candida (especially albicans)

Filamentous
-Fusarium
-Aspergillus
-Scedosporium

56
Q

Name 4 means of pathogenesis for fungal infectious agents.

A

Adhesins
Pseudohyphae in some species
Fungal toxins
Inducing inflammation

57
Q

Can candida albicans be found in healthy individuals?

A

Yes, in 50% of healthy people it is found on most mucous membranes

58
Q

What is the ideal specimen for a suspected fungal infection?

A

Discharge swab, corneal scrapings

59
Q

What can be expected in a microscope image of a suspected fungal infection (4)?

A

Direct examination of pus, corneal scrapings may show yeast/hyphae/spores.

60
Q

On what media do fungi grow, yeast and others?

A

HBA for yeasts or SAB for others.

61
Q

What is the management for a fungal infection? Name a problem with treating fungal infections.

A

Long term antifungal chemotherapy.
Difficult to achieve selective toxicity.

62
Q

What do antifungals often target?

A

The cell membrane of fungi.

OD2 (S1&2) (174 decks)

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