Brucella + Brucellosis Flashcards
1
Q
What are some synonyms for brucellosis?
A
- malta fever
- mediterranean fever
- undulant fever
- contagious abortion
- infectious abortion
- enzootic abortion
2
Q
Describe the microbiology of brucella
A
- gram negative small coccobacilli
- non-motile, non-sporulating
- aerobic, capnophilic, catalase +
- urease + (except B. ovis)
- facultative intracellular
- multiple species
- environmental persistence (withstands drying, temp, pH, humidity)
3
Q
What are the 6 species of Brucella and what types are they?
A
- B.abortus, B. melitensis, B suis - smooth
- possess O=polysaccharide (OPS)
- cause most disease
- B.ovis, B.canis - rough
- do not produce OPS
4
Q
Describe the taxonomy of Brucella
A
- phylum: alpha Proteobacteria
- order: Rhizobiales
- family: Brucellaceae
- genus: Brucella
5
Q
What are the clinical signs in ruminants?
A
- largely sub-clinical until the final trimester
- repro failure, abortion
- most infected cattle will only abort once, but excrete large amounts of bacteria after calving
- calves then born will be weak/ unhealthy
6
Q
What is the main route of introduction for Brucella?
A
- animal movement
- introdction of infected animals into herd/ flock
- shared grazing
7
Q
How does Brucella affect non-pregnant animals?
A
8
Q
Describe the process of infection of Brucella in pregnant and non-pregnant animals
A
9
Q
Clinical signs in pigs?
A
- similar to ruminants
- may see swollen joints and tendon sheaths
- lameness, incoordination
- posterior paralysis
- spondylitis
- abscesses in various organs
10
Q
Clinical signs in horses?
A
- vague lameness
- classically ‘fistulous withers’ - infected bursae
11
Q
Clinical signs in marine animals?
A
- similar to all others
- plus meningoencephalitis
- subcutaneous abscesses
12
Q
Who is at risk for human brucellosis?
A
- cattle ranchers/ dairy farmers
- vets
- abattoir workers
- meat inspectors
- lab workers
- hunters
- travelers
- consumers of unpasteurized dairy products
13
Q
How is zoonotic Brucella transmitted?
A
- conjunctiva or broken skin contacting infected tissues
- ingestion
- inhalation of infectious aerosols
- inoculation with vaccines
- incubation: 7-21 days- several months
14
Q
What are Brucella’s mechanisms of pathogenesis?
A
- intracellular existance in vivo
- facultatively extracellular intracellular pathogen
- reside within non-professional phagocytes such as macrophages and from Brucella containing Vacuoles (BCVs)
- invisible for immune system (stealth pathogen)
- pre-activated macrophages e.g. with IFN-y, successfully kill invading Brucella cells
15
Q
What virulence factors does Brucella lack?
A
- Capsules
- Adhesins
- Fimbriae
- Excreted toxins
16
Q
Describe the Virulence: Type IV secretion system
A
- Injection needle
- injects effector proteins in cytoplasm cell
- T4SS is crucial for establishment of the replicative niche- an endoplasmic reticulum (ER) derived vacoule
- Brucella T4SS mutants are highly attenuated
18
Q
How is microscopy used in diagnostics?
A
- smears of milk, vaginal discharge or placenta
- stamp’s modified Ziehl-Neelsen method
- gram negative bacteria, not truly acid fast, but they are resistant to decolourization by weak acids
