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S&S > Microbiology of Ocular Infections > Flashcards

Microbiology of Ocular Infections Flashcards

1
Q

Extraocular Infections

Blepharitis

A

Infections of the eyelids

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2
Q

Extraocular Infections

Dacryocystitis

A

Infections of the nasolacrimal system

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3
Q

Extraocular Infections

What parts of the eye have normal flora? Few bacteria? Sterile?

A

Normal Flora: eyelid++, conjunctiva+

Very few: cornea

Sterile: intra-ocular tissues

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4
Q

Intraocular Infections

Type of organisms found in conjunctival sac?

A

Gram (+) -> staph, strep, cornye

Occasional gram (-) -> neisseria, moraxella

Fungi = rare & transient

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5
Q

What are the defense mechanisms of the eye? (2)

A
  1. Normal flora of conjunctiva (major role!)
  2. Tears & blinking (contain IgA, lysozyme, lactoferrin)
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6
Q

Extraocular Infections

Etiology of extraocular infections?

A

secondary to other issues:
- trauma (breaks in epithelial barrier of cornea, conjunctiva
- infections in adjacent structures
- KCS
- immunosuppression
- co-infection with other agents (virus infection -> tissue damage -> 2º bacterial invasion)

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7
Q

Intraocular Infections

Etiology of intraocular infections?

A

secondary // the ocular manifestations of systemic infections / disease

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8
Q

Route of entry for extra vs intraocular infections

A

Extraocular: direct inoculation
- opportunistic
- exogenous bacteria
- recrudescene of exisiting infection (e.g., feline herpes virus-1)

Intraocular: systemic infection (bilateral)
- access via uveal or vascular tracts
- immune antigen-antibody complexes typically establish in the uvea
- much less common = direct inoculation (unilateral) (e.g., cat claw injury)

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9
Q

Pathogenesis of ocular pathogens? (4 steps)

A
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10
Q

Steps of diagnosis of ocular infection (4 steps):

A
  1. Thorough ocular exam
  2. Sample collection (eye swab)
  3. Cytology (culture / susceptibility testing where indicated)
  4. Other diagnostic tests (i.e., for definitive dx)
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11
Q

Extraocular Infections

What organisms are the most common cause of blepharitis?

A
  1. Gram (+) cocci (s. pseudointermedius, beta-hemolytic streptococci)
  2. fungi (dermatophytes)
  3. parasites (demodex spp., sarcoptes, cuterebra larvae)
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12
Q

Extraocular Infections

Infection?

A

Blepharitis

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13
Q

Extraocular Infections

Differences between…
Chlamydia felis, Mycoplasma spp., and Pasteurellosis Conjunctivitis?

A

Chlamydia felis
- young cats
- source = carrier animals
- typically presumptive dx

Mycoplasma spp.
- cats, sheep, goats, cattle, birds
- M. felis, M. conjunctivae, M. gallisepticum

Pasteurellosis
- rabbits
- “snuffles” = URI -> conjunctivitis & weeping eyes
- P. multocida

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14
Q

Extraocular Infections

Most common bacterial cause of keratitis?

A

Gram (+) Cocci

S. pseduointermedius, Beta-hemolytic streptococci

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15
Q

Extraocular Infections

Culture of sample from cornea shows heavy growth of Pseudomonas aeruginosa. Significance of the bacteria isolated? Treatment?

A

Bacteria isolated from site with normal flora (cornea) -> Pseudomonas does have ability to cause infection, but requires primary corneal damage to infect

  • Pseudomonas = saprophyte (moist environments), poor pathogen

Treatment = EMERGENCY! -> empirically then modified post culture. Lavage + abx + atropine + NSAIDs + anti-proteinase!

Cornea is a site with REALLY LOW #S OF NORMAL FLORA

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16
Q

Extraocular Infections

Virulence factors // pathogenesis of Pseudomonas aeruginosa?

A

Pili + the production of Matrix Metalloproteinases (melting ulcers!)

Pili = hair-like prjections that aid with bacterial organism with attaching/colonizing/invasion -> produce exotoxins -> kill corneal epithelial cells -> keratits with exudate

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17
Q

Extraocular Infections Pink Eye

Bovine Keratoconjunctivitis - incting cause

A

Moraxella bovis a gram(-) rod
coccobacilli, strict aerobes

18
Q

Extraocular Infections

What predisposes cattle to developing keratoconjunctivitis?

= Pink Eye

A
  • lack pigment around the eye
  • young cattle
  • high UV exposure
  • dry/dust/crowded, stressful conditions
19
Q

Extraocular Infections

Pathogenesis and virulence factors of Moraxella bovis

A

Infected or carrier animals

Mechanical transmission via flying insects (NOT VECTORS!)

  1. Fimbriae (pili)
  2. Hemolysin

Pili allow for attachment / interaction with host cell. Hemolysin are toxic to corneal epithelial cells -> cause damage and induce inflammatory infiltration

20
Q

Extraocular Infections

Potential sequelae of Bovine keratoconjunctivits (pink eye)

A
  1. Globe rupture
  2. Seondary infection -> hypopyon
21
Q

Extraocular Infections

How is Bovine Keratoconjuncivitis prevented / controlled?

A

Vaccination with M. Bovis Bacterin that works against the pili

22
Q

Extraocular Infections

What extraocular infections can fungi cause?

A

Periocular and Surface Ocular Infections!

23
Q

Extraocular Infections

What species is typically affected by fungal keratitis? What are the VFs of these fungi?

Fungal keratitis: aspergillus, fusarium,

A
  • Equine
  • The fungal VFs, impede healing by inhibiting corneal neovascularization and reducing both neutrophil infiltration and cell-mediated phagocytosis
24
Q

Extraocular Infections

Acute conjunctivitis & upper respiratory infection = ?

A

Feline Herpes Virus-1

25
Q

Extraocular Infections

How does feline herpes virus cause persistent infections?

A

Virus maintains latency in host sensory ganglia

26
Q

Extraocular Infections

Sequelae to FHV-1

A
  1. Symblepharon
  2. Eosinophilic keratitis
  3. Conjunctival cys
  4. Sequestrum
  5. KCS OU
27
Q

Extraocular Infections

Dog presents with acute blepharitis, conjunctivis / ocular disease

A

Canine Distemper Virus

28
Q

Extraocular Infections

What causes “Blue Eye” in Canine Adenovirus-1?

A

Diffuse corneal, bilateral, edema. Deposition of immune complexes on epithelium of eye. Type 3 hypersensititvity rxn

29
Q

Intraocular Infections

Presenting complaint is ocular disease. What can this be a manifestation of?

A

Systemic Disease

The eye is often a target organ for systemic diseases

30
Q

Intraocular Infections

Pathogenesis of intraocular infections

A

Infectious agents or immne complexes access the eye via Uvea or vascular tract => establish in uvea and cause infection

31
Q

Intraocular Infections

Inciting cause of Equine Reccurent Uveitis?

An Anterior Uveitis

A

Leptospira spp.

32
Q

Intraocular Infections

Four Gram (-) bacteria causing systemic infections with ocualr manifestation?

A
  1. Enterobacterales (like E. coli)
  2. Histophilus somni
  3. Borrelia burgdorferi
  4. Brucella canis
33
Q

Intraocular Infections

Gram (-) bacteria causing systemic infections with ocualr manifestation.What tick-borne disease often has ocular lesions in dogs?

A

Rickettsial Infections

  1. Ehrlichia canis -> infects monocytes
  2. *Rickettsia rickettsii (rocky mtn. spotted fever) -> causes vasculitis by infecting epithelial cells = ocular hemorrhage
34
Q

Intraocular Infections

How do FCoV -> FIP (dry) lesions manifest as in the eye?

A
  • Bilateral granulomatous anterior uveitis & chorioretinis
  • pyogranulomatous lesions around retinal vessels (white spots)

The granulomatous inflammatory response is a special type of chronic inflammation characterised by often focal collections of macrophages, epithelioid cells and multinucleated giant cells.

Pyogranulomatous inflammation (PI) is a chronic inflammatory lesion characterised by a predominance of macrophages and neutrophils, often in combination with plasma cells and giant cells

35
Q

Intraocular Infections

How does FeLV manifest in the eye?

A

As ocular lymphosarcoma

36
Q

Intraocular Infections

Lesions of canine distemper virus versus canine adenovirus

A

Distemper: Non-granulomaotus chorioretinitis, potentially optic neuritis (=> blindness)

Adeno: uveitis

37
Q

Intraocular Infections

Malignant Catarrhal Fever - ocular manifestations

A
  1. Edema of eyelids and conjuunctiva
  2. Lymphocytic uveitis
  3. photophobia
38
Q

Intraocular Infections

Dimorphic Fungi - manifestations?

A

BELLS

Brain, Eyes, Lungs, Lymph Nodes, Skin

39
Q

Intraocular Infections

Geographic distribution of Histoplasmosis (Histoplasma capsulatum)?

Cats

A

Ohio, Missouri, Mississippi Valley

40
Q

Intraocular Infections

Blastomycosis (Blastomyces dermatidis)
- geographic distribution
- lesions

Dogs

A
  • Mississippi / Ohio Rivers; Central Atlantic States
  • Chorioretinitis, anterior uveitis, endopthalmitis
  • “Big, Blue, Broad-Based Budding”
41
Q

Intraocular Infections

Most common systemic mycotic infection in cats? Source? Lesions?

Can occur in dogs as well

A

Cryptococcosis (Cryptococcus neoformans/gatti)
- Pigeon droplets
- Chororetinitis w/ granulomatous inflammation & retinal detachment; optic neuritis

World-wide distribution

42
Q

Intraocular Infections

Toxoplasma gondii lesion?

A

Chorioretinitis

S&S (53 decks)

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