Genus BRUCELLA
Dr.P.Sreenivasulu Reddy MD.,
Professor of Microbiology
NARAYANA MEDICAL COLLEGE
Nellore-1
Andhra Pradesh INDIA
Many Names of Brucellosis
Human Disease
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Malta Fever
Undulant Fever
Mediterranean Fever
Rock Fever of Gibraltar
Gastric Fever
Animal Disease
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Bang’s Disease
Enzootic Abortion
Epizootic Abortion
Slinking of Calves
Ram Epididymitis
Contagious Abortion
Sir William Burnett
(1779-1861)
•Physician General to
the British Navy
•Differentiated the
various fevers
affecting soldiers
Jeffery Allen
Marston
•Contracted Malta
fever.
•Described his own
case in great detail.
Sir David Bruce
(1855-1931)
•British Army physician
and microbiologist
•Discovered Micrococcus
melitensis (July 9, 1887)
Bernhard Bang
(1848-1932)
•Danish physician and
veterinarian
•Discovered Bacterium
abortus (1897) could
infect cattle, horses,
sheep and goats.
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Alice Evans, American bacteriologist
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Credited with linking the organisms
Similar morphology and pathology
between:
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Bang’s Bacterium abortus
Bruce’s Micrococcus melitensis
Nomenclature today credited to
Sir David Bruce
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Brucella abortus and Brucella melitensis.
Morphological Profile
Brucella spp. are small,
Gram-negative, non-motile,
non-spore-forming,
coccobacilli .
Intracellular microbes
causing chronic disease.
Cultural characters
Aerobe.
Best medium is Trypticase
Soya Agar with selective
agents
(Polymyxin,Cyclohexamide).
Small,moist,translucent and
glistening colonies after 3 or
more days of incubation.
Species
Biovar/
Serovar
Natural Host
Human
Pathogen
B. abortus
1-6, 9
cattle
yes
B.melitensis
1-3
goats, sheep
yes
B. suis
1, 3
swine
yes
2
hares
yes
4
reindeer, caribou
yes
5
rodents
yes
B. canis
none
Dogs
yes
B. ovis
none
Sheep
no
B. neotomae
none
Desert wood rat
no
marine mammals
?
B. maris (?)
Biochemical reactions
Catalase and Oxidase positive.
Nitrates are reduced.
Rapidly positive for urease.
Negative for IMViC reactions.
Susceptibility
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Killed at 600 C in 10 minutes
Pasteurization of milk .
Survival is long in refrigerated milk,
ice creams and cheese.
Transmission to Humans
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Conjunctiva or broken skin on contact with
infected tissues
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Blood, urine, vaginal discharges, aborted
fetuses, placentas
Ingestion
Raw milk & unpasteurized dairy products
(Cheese)
 Rarely through undercooked meat
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Transmission to Humans
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Inhalation of infectious aerosols
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Inoculation with vaccines
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B. abortus strain 19, RB-51
B. melitensis Rev-1
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Conjunctival splashes, injection
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Pens, stables, slaughter houses
Person-to-person transmission is rare
Incubation varies
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5 days to three months
Transmission in Animals
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Ingestion / contact with infected
tissues or body fluids
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Venereal
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Mucous membranes, injections
Swine, sheep, goats, dogs
Fomites
Who is at Risk?
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Occupational Disease
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Cattle ranchers/dairy farmers
Veterinarians
Abattoir workers
Meat inspectors
Lab workers
Hunters
Travelers
Consumers of unpasteurized dairy products
Pathogenecity and Immunity
Followed by Entry
Ingested by PMN and not killed (super oxide dismutase ,LPS and
nucleotide substance).
Spread to local LN, multiply and spread to blood.
Reaches to RES (Spleen,Liver,BM,LN).
Resist phagocytosis (production of AMP/GMP and TNF Inhibits the
phagolysosome fusion).
Spread (CNS,Heart,Joints,Respiratory,Skin,GU system)
Host response leads to granuloma formation and necrosis.
B. abortus
(Contagious/ Infectious abortion)
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Worldwide
Some countries have
eradicated it
Notifiable disease
in many countries
abortions, arthritic joints.
 Fever of Unknown Origin (FUO)
Main causes for spontaneous abortion in animals are erythritol, which can promote infections in the fetus and
placenta and lack of anti-Brucella antibody in amniotic fluid.
B. canis
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Poorly understood
1-19% prevalence in United
States
contact with aborted fetuses
and semen.
Rarely causes disease in
humans.
B. suis
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Biovars 1 and 3
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Free
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United Kingdom, Canada
Eradicated
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Worldwide problem.
Holland, Denmark
Low Incidence
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Middle East, North Africa
Human Disease
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Can affect any organ or system
All patients have a cyclical fever
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Headache, weakness,
arthralgia, depression,
weight loss, fatigue,
liver dysfunction
Human Disease
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20-60% of cases
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Osteoarticular complications
 Arthritis, spondylitis, osteomyelitis
Hepatomegaly may occur
Gastrointestinal complications
2-20% of cases
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Genitourinary involvement
 Orchitis and epididymitis most common
Human Disease
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Neurological
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Cardiovascular
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Endocarditis resulting in death
Chronic brucellosis is hard to define
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Depression, mental fatigue
Length, type and response to treatment variable
Localized infection
Blood donations of infected persons should not
be accepted
Human Disease
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Congenitally infected infants
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Low birth weight
Failure to thrive
Jaundice
Hepatomegaly
Splenomegaly
Respiratory difficulty
General signs of sepsis (fever, vomiting)
Asymptomatic
Chronic brucellosis:
It is hard to define
- Length, type and response to
treatment variable
The localized form:
-Bones and joints.
-Lumbar spondylodiscitis,
sacroiliitis is typical.
-Orchitis also frequent.
Sequelae are highly variable
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Granulomatous hepatitis,
Arthritis, spondylitis,
Anaemia, leukopenia,thrombocytopenia,
Meningitis, uveitis, optic neuritis,
- Endocarditis.
Granuloma of Liver
Diagnosis in Humans
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Isolation of organism
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Blood, bone marrow, other tissues
Serum agglutination test
Four-fold or greater rise in titer
 Samples 2 weeks apart
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Immunofluorescence Method
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Organisms in clinical specimens
PCR
Blood cultures in trypticase
soya broth (Castaneda’s
method): Biphasic medium.
Sample inoculated bottle has to
be tilted to flow the broth over
solid medium and keep it upright
position at 370C.
The growth of brucellae is
extremely slow.
Bone marrow cultures are more
sensitive than blood.
Demonstration of IgM , IgG and Ig A
ELISA is the best method.
Standard tube agglutination test:
Anti -O-polysaccharide of LPS. Killed strains of
B. abortus as antigen. Not useful for B.canis.
Modified Tube agglutination test:
2-mercaptoethanol is added to serum before
testing which causes disruption of IgM and
only IgG are detected.
Problems with TA test: Prozone phenomenon, Presence of blocking or non-agglutinating antibodies. False positives with cholera, tularemia,yersinia or vaccination
.
Contd…..
Castaneda strip test: Strip with colored brucella antigen. On
addition of patients serum, if antibodies are present, prevents
the flow of serum.
Brucellin Skin test: Delayed hypersensitivity.
Molecular techniques: PCR
Radiology: Alterations in infected vertebrae; Pedro Pons sign
( erosion of antero-superior corner of lumbar vertebrae)
and marked osteophytosis are suspecious of brucellic
spondylitis.
Diagnosis in Animals
Culture of urine and Milk.
Rapid latex agglutination test,
Rose Bengal card test. (Rose Bengal + B.abortus +
Sodium azide)
Contd….
Milk Ring Test: Frequently used test.
A drop of colored brucella antigen
(B.abortus/B.melitensis with hematoxylin) is added to
milk in a test tube, incubated in a water bath at
700C for 40-50 minutes.
Positive: Blue ring at the top leaving the milk
unstained.
Negative: No ring. Milk remains uniformly blue.
Treatment of Choice
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Combination therapy has the best efficacy
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Doxycycline for 6 weeks in combination with
Streptomycin for 2-3 weeks or Rifampin for 6
weeks
CNS cases to treat for 6-9 months.
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Same for endocarditis cases plus surgical
replacement of valves.
Prognosis
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May last days, months, or years
Recovery is common
Disability is often pronounced
About 5% of treated cases relapse
Failure to complete the treatment regimen
 Sequestered infection requiring surgical drainage
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Case-fatality rate: <2% ( untreated)
 Endocarditis caused by B. melitensis
Prevention and Control
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Education about risk of transmission
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Wear proper attire if dealing with
infected animals/ tissues
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Farmer, veterinarian, abattoir worker,
butcher, consumer, hunter, public
Gloves, masks, goggles
Avoid consumption of raw dairy
products
Prevention and Control
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Immunize in areas of high prevalence
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Young goats and sheep with Rev-1
Calves with RB51
No human vaccine
Eradicate reservoir
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Identify, segregate, and / or cull
infected animals
References:
www.slideshare.net