Microbiology of Ocular Infections Flashcards by Kate Karlen

Extraocular Infections

Blepharitis

Infections of the eyelids

How well did you know this?

Not at all

Perfectly

Extraocular Infections

Dacryocystitis

Infections of the nasolacrimal system

How well did you know this?

Not at all

Perfectly

Extraocular Infections

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

Normal Flora: eyelid++, conjunctiva+

Very few: cornea

Sterile: intra-ocular tissues

How well did you know this?

Not at all

Perfectly

Intraocular Infections

Type of organisms found in conjunctival sac?

Gram (+) -> staph, strep, cornye

Occasional gram (-) -> neisseria, moraxella

Fungi = rare & transient

How well did you know this?

Not at all

Perfectly

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

Normal flora of conjunctiva (major role!)
Tears & blinking (contain IgA, lysozyme, lactoferrin)

How well did you know this?

Not at all

Perfectly

Extraocular Infections

Etiology of extraocular infections?

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)

How well did you know this?

Not at all

Perfectly

Intraocular Infections

Etiology of intraocular infections?

secondary // the ocular manifestations of systemic infections / disease

How well did you know this?

Not at all

Perfectly

Route of entry for extra vs intraocular infections

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)

How well did you know this?

Not at all

Perfectly

Pathogenesis of ocular pathogens? (4 steps)

How well did you know this?

Not at all

Perfectly

Steps of diagnosis of ocular infection (4 steps):

Thorough ocular exam
Sample collection (eye swab)
Cytology (culture / susceptibility testing where indicated)
Other diagnostic tests (i.e., for definitive dx)

How well did you know this?

Not at all

Perfectly

Extraocular Infections

What organisms are the most common cause of blepharitis?

Gram (+) cocci (s. pseudointermedius, beta-hemolytic streptococci)
fungi (dermatophytes)
parasites (demodex spp., sarcoptes, cuterebra larvae)

How well did you know this?

Not at all

Perfectly

Extraocular Infections

Infection?

Blepharitis

How well did you know this?

Not at all

Perfectly

Extraocular Infections

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

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

How well did you know this?

Not at all

Perfectly

Extraocular Infections

Most common bacterial cause of keratitis?

Gram (+) Cocci

S. pseduointermedius, Beta-hemolytic streptococci

How well did you know this?

Not at all

Perfectly

Extraocular Infections

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

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

How well did you know this?

Not at all

Perfectly

Extraocular Infections

Virulence factors // pathogenesis of Pseudomonas aeruginosa?

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

How well did you know this?

Not at all

Perfectly

Extraocular Infections Pink Eye

Bovine Keratoconjunctivitis - incting cause

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

Extraocular Infections

What predisposes cattle to developing keratoconjunctivitis?

= Pink Eye

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

Extraocular Infections

Pathogenesis and virulence factors of Moraxella bovis

Infected or carrier animals

Mechanical transmission via flying insects (NOT VECTORS!)

Fimbriae (pili)
Hemolysin

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

Extraocular Infections

Potential sequelae of Bovine keratoconjunctivits (pink eye)

Globe rupture
Seondary infection -> hypopyon

Extraocular Infections

How is Bovine Keratoconjuncivitis prevented / controlled?

Vaccination with M. Bovis Bacterin that works against the pili

Extraocular Infections

What extraocular infections can fungi cause?

Periocular and Surface Ocular Infections!

Extraocular Infections

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

Fungal keratitis: aspergillus, fusarium,

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

Extraocular Infections

Acute conjunctivitis & upper respiratory infection = ?

Feline Herpes Virus-1

# **Extraocular Infections** How does feline herpes virus cause persistent infections?

Virus maintains ***latency* in host sensory ganglia**

# **Extraocular Infections** Sequelae to FHV-1

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

# **Extraocular Infections** Dog presents with acute blepharitis, conjunctivis / ocular disease

Canine Distemper Virus

# **Extraocular Infections** What causes "**Blue Eye**" in *Canine Adenovirus-1*?

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

# **Intraocular Infections** Presenting complaint is ocular disease. What can this be a manifestation of?

**Systemic Disease** | The eye is often a target organ for systemic diseases

# **Intraocular Infections** Pathogenesis of intraocular infections

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

# **Intraocular Infections** Inciting cause of **Equine Reccurent Uveitis**? | An **Anterior Uveitis**

*Leptospira* spp.

# **Intraocular Infections** Four **Gram (-)** bacteria causing systemic infections with ocualr manifestation?

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

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

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

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

- Bilateral granulomatous anterior uveitis & chorioretinis - pyogranulomatous lesions around retinal vessels (white spots) ## Footnote 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**

# **Intraocular Infections** How does **FeLV** manifest in the eye?

As **ocular lymphosarcoma**

# **Intraocular Infections** Lesions of **canine distemper virus** versus **canine adenovirus**

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

# **Intraocular Infections** Malignant Catarrhal Fever - ocular manifestations

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

# **Intraocular Infections** Dimorphic Fungi - manifestations?

**BELLS** | Brain, Eyes, Lungs, Lymph Nodes, Skin

# **Intraocular Infections** **Geographic distribution** of Histoplasmosis (*Histoplasma capsulatum*)? ## Footnote **Cats**

Ohio, Missouri, Mississippi Valley

# **Intraocular Infections** **Blastomycosis (*Blastomyces dermatidis*)** - geographic distribution - lesions ## Footnote **Dogs**

- Mississippi / Ohio Rivers; Central Atlantic States - Chorioretinitis, anterior uveitis, endopthalmitis - *"Big, Blue, Broad-Based Budding"*

# **Intraocular Infections** Most common systemic mycotic infection in cats? Source? Lesions? ## Footnote Can occur in dogs as well

**Cryptococcosis (*Cryptococcus neoformans/gatti*)** - Pigeon droplets - Chororetinitis w/ granulomatous inflammation & retinal detachment; optic neuritis ## Footnote World-wide distribution

# **Intraocular Infections** ***Toxoplasma gondii*** lesion?

Chorioretinitis