Moraxella & Francisella Flashcards
What is unique about Moraxella bovis structure?
appears as a Gram-negative diplococci —> not a true coccus, cells are rod-shaped around a penicillin disk
What respiration and fermentation does Moraxella bovis undergo?
- strict aerobes
- nonsaccharolytic: oxidizes sulfur and nitrogen (amino acids)
What infection does Moraxella bovis cause? What are the clinical signs?
infectious bovine keratoconjunctivitis (IBK, bovine pinkeye)
- conjunctivitis
- keratitis
- corneal ulceration
- more than 5% of herd infected
Where is Moraxella bovis commonly found? How is it transmitted? What is required for infection?
normal flora in upper respiratory tract
direct contact with fomites (grass), flies, dust
attachment to the eye and colonization
What are 5 predisposing factors to Moraxella bovis infection? How is infection commonly controlled?
- sunlight (UV) - irritation
- breed - non-hooded eyelids (Herefords)
- flies - transmission
- irritation - dust, grass
- prior infection
protect the eye from irritants (eye patches)
What cattle are more suscpetible to Moraxella infection?
- less than 2 years old (lower immnuity)
- those with non-hooded eyelids (Herefords)
What is a corneal pannus?
common presentation of Moraxella bovis infection - subepithelial fibrovascular tissue ingrowth occurs from the limbus onto the cornea, usually resulting from inflammation from chronic irritation
Moraxella bovis, pinkeye:
corneal opacity due to intraocular fluid pressure + bright red rim of pannus formation
Moraxella bovis, pinkeye:
ulcer in localized area of corneal opacity
- no pannus formation with shallow lesions
Moraxella bovis, pinkeye:
small corneal scar due to incomplete healing
- B = artifact from flash
What is a staphyloma?
secondary infection of Staphylococcus aureus in the resulting ulcer left from Moraxella bovis, resulting in a deep ulcer perforating through the aqueous humor
- Staph. is common on skin and less fastidious, so it will be an opportunistic pathogen and commonly found in a culture with Moraxella
Moraxella bovis, pinkeye:
healing ulcer that has lost its red appearance
How does Moraxella bovis infection cause increased intraocular pressure? What does this result in?
impairs the drainage of aqueous humor —> glaucoma
damages the optic nerve due to increased pressure and chronic inflammation
Moraxella bovis, pinkeye:
- secondary infection of the eye (endophthalmitis) with purulent inflammation and pus in the anterior chamber
- pannus formation
- white and irregular cornea
- sight permanently lost due to scar formation, pus buildup, and glaucoma
What are the 2 major virulence factors of the virulent strains of Moraxella bovis?
- β-hemolysin - enhances lesion formation
- highly piliated - sticks to plate/eye