Brucella Flashcards
What does Brucella cause?
Abortion in animals and foodborne zoonosis for humans
Where was brucella first discovered?
In small cocci in the spleen
What is the basic microbiology of brucella?
- Gram negative
- Small coccobacilli
- Aerobic, Capnophillic (thrive in high CO2), Catalase +
- Faculative intracellular
- Has environmental persistence
- Non-Sporulating
What are the 6 classical species of Brucella?
- B. abortus
- B. melitensis
- B. suis
- B. canis
- B.ovis
- B. neotomae
What species are smooth/ possess the O-polysaccharide?
B. abortus, B. melitensis & B. suis
What species are naturally rough/ do not produce OPS?
B. ovis & B. canis
What type of Brucella are more pathogenic?
Smooth
What is the taxonomy of Brucella?
Phylum: α-Proteobacteria
* Order: Rhizobiales
* Family: Brucellaceae
* Genus: Brucella
What has brucella derived from?
soil dwelling plant associate
What is important about ruminant abortion
- Only in the last trimester
- they only abort once from the infection
- next pregnnacy they excrete the bacteria- milk/ calf may be infecred
Where is the significant shedding of brucella in ruminants?
Through milk
How is brucella transmissed?
- Shared grazing
- Importation of animals
Why does brucella not effect human pregnancies?
Humans do not produce the hormone erythitol
How does brucella cause abortion in a pregnant animal carrying it?
- Erythitol is produced by placental cells in the final trimester
- Brucella is attracted to the placenta-due to the erythitol
- Invasion of the placenta via erythropathogenic cells
- Causes an inflammatory response -> tissue damage -> abortion
What are the clinical signs of brucella in pigs?
- Similiar to ruminants
- may see swollen joints and tendon sheaths, lameness and incoorrdination
How do we control brucella in animals?
Culling rather than Treating
What are the clinical signs of brucella in horses?
- Vague lameness
- ‘fistulous’ withers
How many chromosones does Brucella have and what are their total size?
- 2 chromosones
- total size = 3.3 Mbp
What can release large quantities of Brucella into the environment?
Abortion or live birth from an infected animal
What is the most significant brucella symptom in males?
Orchitis
In what herds is their most likely to be ‘extreme’ abortion storms?
Naive herds, may be abortion storms of up to 50%
How may Brucella be passed on into humans?
- Conjunctiva or Broken skin comes into contact with infected tissue
- May be ingested/ e.g raw milk
- Inhalation of infectious aerosols
- Inoculation with vaccines
What is the average incubation of brucella?
7-21 days to several months
What are the most common symptoms of Brucella in humans?
- Flu-Like, e.g anorexia, fatigue, weight-loss
- Hepatosplenomegaly, Lymphadenopathy
- primarily a febrile disease
How is Brucella Treated?
Antibiotic treatment- doxycycline, streptomycin
What usually causes death in humans?
this is rare <2%
endocarditis, meningitis
What percentage of treated cases relapse?
Around 5%
Where does Brucella mainly reside?
aka what cell
within non-professional and professional phagocytes such as
macrophages & form Brucella Containing Vacuoles (BCVs)
this makes it invisible to the immune system
How does the Type IV secretion system work?
- Injects effector proteins into the cytoplasm cell
- T4SS is crucial for establishment
of the replicative niche –
an endoplasmic reticulum
(ER) derived vacoule. - Brucella T4SS mutants are
highly attenuated
Give 5 ways you could diagnose Brucella
- Serological testing
- Milk testing
- Culture Abortion Products
- Bacteriological identification
- Tissue collected post-mortem
rose-bengal test is the most common
What two infectious agents may resemble Brucella?
- Coxiella
- Chlamydia
What growth media would you use to grow Brucella?
Farrels medium containing horse serum
* 10% CO2
* Selective Enrichment used for blood
What are the best ways we can control Brucella?
- Pasteurisation of milk
- Vaccination of cattle, sheep and goat in enzootic areas
- Eradication testing and culling
- Continued surveillance of milk and blood
- Epidemiological tracing
What category is Brucella in terms of Biological Warfare?
Category B
* Moderately easy to disseminate
* causes moderate morbidity and low mortality
What does Brucella form when it resides within non-professional and ‘professional’ phagocytes?
Brucella Containing Vacuoles
What is a ‘Brucella Containing Vacuole’?
They are invisible to the immune system and therefore known as stealth pathogens
What type of Phagocytes can kill Invading Brucella?
Pre-Activated Macrophages, e.g with IFN-Y
What Virulence Factors does Brucella lack?
- Capsules
- Adhesins
- Fimbriae
- Excreted Toxins
What is the function of the T4SS?
- Injects effector proteins into the cytoplasm cell
- T4SS is crucial for the establishment of the replicative niche
- The Brucella T4SS are highly attenuated
What is the most widely used screening test for Brucella?
Rose Bengal Plate Test
How may you diagnose Brucella?
- Serological testing
- Testing of Milk
- Smear Examination
- Culture of abortive products
- Tissues collected post-mortem
- Bacterial Identification
How could you diagnose Brucella using microscopy?
- Using smears of milk, vaginal discharge or placenta
- Stamps’ modified Ziehl-Neelson Method
What are Brucella resistant to?
Brucella are not truly acid-fast but are resistant to decolourisation by weak acids
What other infectious agents may resemble brucella?
- Coxiella Burnetti
- Chlamydia
How would you culture Brucella?
- Due to slow growth- Selective media are usually required on primary culture
- 10% CO2
- Selective media such as Farrels medium
- Serum dextrose agar is generally recommended for subculture
- Selective enrichment for blood
How would you diagnose Brucella using blood typing?
- Serology is based on the reference OPS
- Growth on media-containing dyes
- CO2 is a requirement, H2S is produced
What media containing dyes are acceptable for Brucella?
- Thionin
- Basic Fuchsin
What molecular tests are available for Brucella?
- Tandem repeats/ Variable Repeats
- Multilocus sequence typing
- PCR based on mobile elements
What part of the Brucella is immunogenic?
LPS Surface antigen
In what secretions are Brucella antibodies present?
In Serum and Milk
What are important issues that should be brought up in the brucella vaccination programme?
- Cost
- Sensitivity
- Specificity
Why should you not use live vaccines in pregnant animals?
Live vaccine strains retain residual virulence
What do you need to be able to safely handle brucella?
- Safety cabinets
- Negative pressure
- Fumigation
What is the WHO risk group 3?
pathogens that pose a high risk to the worker but only a low risk to the community
What agar is generally only recommended for subculture?
Serum dextrose agar
What organisms share epitopes and may cause a cross-reaction with brucella?
- Yersinia enterocolitica
- E.Coli 0:157
How do you reduce an area from high brucella prevalence to low brucella prevalence?
Cattle: B. abortus S19 (smooth) or RB51(rough)
* Sheep & Goats: B. melitensis Rev1 (smooth)
* No vaccine for swine
* No vaccine for humans (all remain virulent in humans)
Why should you not use the vaccines in pregnant animals?
if the live vaccine strains contain residual virulence
