Moraxellaceae

Question 1

Moraxellaceae - general characteristics

Answer 1

Small, GN

• nonmotile
• aerobic rods
• non fermentative
• oxidase and catalase positive
• commensal of the nasopharynx and conjunctiva of cattle

Question 2

M. bovis

Answer 2

Causes infectious bovine keratoconjunctivitis (IBK)

- pinkeye in cattle

Question 3

M. bovis is most common in _______

Answer 3

Beef cattle

- range from mild conjunctivitis to severe ulceration, corneal perforation, and blindness

Question 4

What happens after initial infection?

Answer 4

Edema and neutrophilic inflammation

- progress to severe edema = corneal opacity, ulceration, potential rupture with uveal prolapse

Question 5

M. bovis is aggravated by

Answer 5

Exposure to sunlight, tall grass, dry dusty wind, and insects

Question 6

What type of fimbriae does M. bovis have?

Answer 6

Type 4

• mediates adherence and colonization to corneal and conjunctival epithelial cells
• undergo phase variation
• 7 serological types

Question 7

______ is required for virulence

Answer 7

RTX cytotoxin

• pore forming toxin with specificity for conjunctival and corneal epithelial cells and neutrophils
• destruction of conjunctival/corneal cells = inflammation
• neutrophils are recruited and are lysed = tissue destruction

Question 8

What other bacteria also has RTX cytotoxin?

Answer 8

Actinobacillus pleuropneumoniae

Question 9

Diagnosis

Answer 9

Isolated on blood agar

• RTX produces beta hemolysis
• nonfermenter, nitrate not reduced, indole negative

Question 10

Treatment and control

Answer 10

• control irritants
• insect control
• oxytetracycline and florfenicol are preferred treatments
• subconjunctival antibiotics
• surgery or eyepatch

Question 11

What to do in outbreak situations

Answer 11

Add chlortetracycline to feed for 30 days

Question 12

If non responsive?

Answer 12

Culture for mycoplasma bovis or chlamydia