Mannheimia Flashcards
Pasteruella pneumotropica
Commensal in laboratory rodents
- rats and mice are primary carriers
- transmitted via direct contact
- does not survive in environment
- conjunctivitis, rhinitis, otitis, cervical lymphadenitis
Capsular antigens are determined by a _______ in M. haemolytica
Number
- all begin with the letter A
Growth properties of M. haemolytica
- grows on MacConkey agar
- beta hemolysis
- indole negative
Virulence factors of M. haemolytica
- LPS: long O chain, endotoxin to complex with leukotoxin to stabilize leukocytic activity
- capsule: inhibits complement, phagocytosis, intracellular killing, and enhances neutrophil recruitment and adhesion to alveolar epithelium
- fimbriae: enhance colonization of URT
Leukotoxin
Poreforming cytolysin that affects ruminant leukocytes and platelets by altering function at low levels and causing lysis at high levels
- required for BRD lesions!!
- RTX family of cytolytic toxins
Leukotoxin prefers _____
Neutrophils over mononuclear cells
- stimulates release of IL-1 and TNF-alpha from mononuclear cells
What are the different functions of leukotoxin at a high versus low dose?
- low dose: activates PMNs and stimulates degranulation
- high dose: neutrophil lysis due to membrane disruption
- higher dose: induces neutrophil apoptosis
= massive inflammatory cell recruitment and inflammatory mediator release, tissue destruction
M. haemolytica is the primary agent of ________ in cattle
Bovine respiratory disease (shipping fever)
- bronchopneumonia may or may not be present
- A1, sometimes A2 (common in normal calves before shipment)
M. haemolytica also causes ______ and ______
Mastitis in cows and broncopneumonia and mastitis in sheep
Treatment of M. haemolytica
Same as P. multocida
- M. haemolytica and P. multocida combination bacterins are inconsistent
- only prevention is good management
Bibersteina trehalosi
- septicemic pasteurellosis in feeder lambs (5-12 months)
- resembles bovine hemorrhagic septicemia w/out intestinal involvement
- lower morbidity rate
- stress associated
- found in tonsils of carrier sheep
Avibacterium paragallinarum
Requires V factor (NAD)
- will grow on blood agar with staph streak
- forms small colonies at 24-48 hrs
A. paragallinarum disease
Infectious coryza
- occurs in growing chickens or layers
- nasal discharge, sneezing, facial edema, conjunctivitis, lacrimation
- anorexia and diarrhea
- acute or chronic form
- leads to septicemia and arthritis with secondary bacterial infection
- increased culls and decreased egg production
A. paragallinarum diagnosis
Difficult to diagnose via culture due to slow growth and fastidious nature (is overgrown)
- serologic detection of serum antibodies by agglutination
- PCR detection is effective
A. gallinarum
Commensal in URT of chickens
- occasionally causes a low grade respiratory infection in chickens
Actinobacillus
Small, GN rod, facultative anaerobes, nonmotile
- resemble pasteurella morphologically and biochemically
Principle species of actinobacillus
- pleuropneumoniae: swine pleuropneumonia
- suis: septicemia in young pigs
- lignierseii: bovine actinomycosis
- equuli: sleepy foal disease
- capsulatus: arthritis in rabbits
What is the only specie of actinobacillus that is not a commensal?
Pleuropneomoniae
- occurs as a primary pathogen
A. pleuropneumoniae disease characteristics
Serofibrinous pleuritis and fibrinous pneumonia
- occurs in 2-6 month olds
- fever, anorexia, acute respiratory distress, death in 24 hrs
- concurrent septicemia, meningitis, arthritis
- up to 24% mortality
A. pleuropneumoniae virulence factors
- LPS
- capsule: antiphagocytic, required for virulence, designated by a number
- 4 RTX toxins: Apxl, Apxll, Apxlll, ApxlV
What is responsible for lung pathology?
RTX toxins
- lyse macrophages and neutrophils at high doses, activate and cause degranulation at low doses
- lyse alveolar epthelial cells and erythrocytes
- Apxl is most cytolytic, followed by Apxlll, and Apxll
What does A. pleuropneumoniae require for growth?
NAD
- beta hemolytic
Capsular types
1-12
- serotypes 1 and 5 are most common in North America
- 2 is common in Europe
Antibodies against RTX
Protective, but not effective
- bacterins only provide partial protection
- live attenuated (nonencapsulated) strains are effective, produce RTX toxins in native state
