Module 5.7 Gram Negative Flashcards
Pasteurellaceae family
- small gram negative
- facultative anaerobic coccobacilli
- nutritionally fastidious
- residents on mucosal surfaces (URT)
- poorly survive in environment
- host specific
- extracellular pathogens, toxins are important
What are the three main genera within the Pasteurellaceae family?
Pasteurella, Mannheimia, Actinobacillus
What is an oxidase test?
It tests for the presence of cytochrome c oxidase in gram negative bacteria. It is absent in anaerobes but present in Pasteurellaceae, Alcaligenaceae, Pseudomonas.
Main virulence factors of the Pasturella species
- capsule
- adhesins
- iron-acquisition systems
- toxins
Case Report:
- baby sparrow rescued from cat, sparrow becomes droopier and sleepier over the next 2 days then eventually dies
What could be a common cause?
It died of septicemia caused by Pasteurella multocida
Pasteurella multocida 1-OPP/PR-Z (Bite)
- commonly see fowl cholera causing septicemia in birds of all types (capsule Type A)
- often secondary to pneumonia in pigs (capsule Type A)
- often seen in rabbit pasteurellosis (capsule Type A)
Treatment and prevention of Pasteurella multocida?
- antimicrobial treatment prophylaxis
- beta-lactams
- sulphonamide
- currently only resistant to tetracyclines
- there are vaccines for different species/conjunct issues
Case Report:
- calf underwent shipping stress and mixture, low temp, high humidity, poor ventilation
- 3 days off feed, DROOPING head, fever, tachycardia, tachypnea
- clinically had rhinitis, cough, nasal discharge
- necropsy showed inflammation lesions in lung
What do we suspect?
Mannheimia hemolytica!
Mannheimia hemolytica 1-OPP-PR
- normal in URT of cattle and sheep
- several serotypes, variable virulence
- main pthogen is bovine respiratory disease complex BRDC
- most common and costly disease in NA beef cattle
- causes septicemia and pneumonia in sheep
What is the pathogenesis of Mannheimia hemolytica?
- host innate immunity is evaded
- capsule provides resistance to phagocytosis
- leukotoxin RTX toxin kills alveolar macrophages and PMNs
- often a mixed bacterial infection
Treatment and prevention of Actinobacillus pleuropneumoniae?
- antibiotics but increasing resistance
- vaccination
- management based on serological status (do not mix pigs of different status)
Treatment and prevention of Mannheimia hemolytica?
- control predisposing factors
- preconditioning to adapt to bunk feed, dehorning, socializing, deworming, vaccinations, etc.
- prophylactic antibiotics but resistance is becoming a real problem
- good hygiene management
Actinobacillus pleuropneumoniae 2-OPP-PR
- common commensal of the tonsils
- fastidious nutritional requirements
- hemorrhagic fibrinous pleuropneumoniae
- many serotypes and RTX toxins
- serotypes vary in virulence, most virulent express ApxI and ApxII
Actinobacillus suis 2-OPP
- very similar to A. pleuropneumoniae
- septicemia and pneumonia
- broader host range
- ApxI, ApxII, LPS and capsule important virulence factors
Haemophilus species
- small gram negative coccobacilli
- blood loving
- fastidious
- common commensals on mucosal surfaces
- 2 main species: Glaesserella and Histophilus
