Brucella
Brucella
Brucella
− Gram negative rod shaped − Nonmotile
− Nonencapsulated
− In tissues are found intracellularly
− Most clinical isolates come from blood cultures
− Requires enriched media containing meat infusion or tryptone
− Will grow on CBA or chocolate agar
− Growth is slow and may take 72 hours
Brucella
Brucella
•
Classification
− Are all intracellular organisms − 4 species can infect humans
B. abortus B. suis
B. melitensis B. canis
− Morphology and cultural characteristics
Brucella
Brucella
− B. abortus requires 10% CO2 for growth,
others do not • Biochemistry
− Oxidase +
− Nonfermentative
− Urease +\catalase +
− H2S produced by B. abortus and B. suis
− Speciated based on the ability to grow in the
Brucella
Brucella
• Antigenic structure
− 2 antigens that are part of the LPS are
recognized: A and M
B. melitensis has the highest concentration of M and
causes the most serious infections
• Virulence factors
− Endotoxin
• Clinical significance
− Has a tropism for erythritol
Animal fetal tissues and placenta, other than those in
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, other
canids yes
B. ovis none sheep no
B. neotomae none Desert wood rat no
History
Sir David Bruce (1855-1931)
•British Army physician and
microbiologist who discovered
Micrococcus melitensis
Bernhard Bang (1848-1932)
•Danish physician and veterinarian Discovered
The Many Names of Brucellosis
The Many Names of Brucellosis
Human Disease
• Malta Fever
• Undulant Fever
• Mediterranean Fever • Rock Fever of
Gibraltar
• Gastric Fever
Animal Disease
• Bang’s Disease
• Enzootic Abortion • Epizootic Abortion • Slinking of Calves • Ram Epididymitis
Transmission
Transmission to Humans
Transmission to Humans
•
Conjunctiva or broken skin
contacting infected tissues
− Blood, urine, vaginal discharges,
aborted fetuses, placentas
•
Ingestion
− Raw milk & unpasteurized dairy
products
Transmission to Humans
Transmission to Humans
• Inhalation of infectious aerosols
− stables, slaughter houses
• Person-to-person transmission is very rare • Incubation varies
Transmission in Animals
Transmission in Animals
•
Ingestion of infected tissues
or body fluids
•
Contact with infected tissues
or body fluids
Epidemiology
Who is at Risk?
Who is at Risk?
•
Occupational Disease
− Cattle ranchers/ dairy farmers − Veterinarians
− Abattoir workers − Meat inspectors − Lab workers
Consumers of
unpasteurized
B. melitensis
B. melitensis
•
Latin America, Middle East,
Mediterranean, eastern Europe,
Asia, and parts of Africa
•
Accounts for most human cases
− In the Mediterranean and MiddleEast
Up to 78 cases/100,000
people/year
•
Recent emergence in cattle on
B. abortus
B. abortus
•
Worldwide
•
Some countries have
eradicated
•
Notifiable disease in many
countries
− Poor surveillance and
reporting due to lack of recognition
− Fever of Unknown Origin
B. suis
B. suis
•
Biovars 1 and 3
− Worldwide problems where swine are
raised
•
Free
− United Kingdom, Canada
•
Eradicated
− Holland, Denmark
•
Low Incidence
B. canis
B. canis
•
Poorly understood
•
1-19% prevalence in
United States
Brucellosis
Brucellosis
Human Disease
Human Disease
•
Can affect any organ or organ
system
•
All patients have a cyclical fever
(unduland fever)
•
following ingestion of contaminated
milk or cheese from goats (
B.
melitensis
), cows (
B. abortus
), pigs
Brucella
Brucella
Clinical manifestations range from subclinical, to
chronic with low grade symptoms of low fever and muscular stiffness, to acute with fever and chills.
The fever typically spikes each evening and
this coincides with the release of organisms from phagocytes (hence the name undulent fever).
The patient may also experience malaise,
Human Disease
Human Disease
•
20-60% of cases
− Osteoarticular complications
Arthritis, osteomyelitis
•
Hepatomegaly may occur
•
Gastrointestinal complications
•2-20% of cases
− Genitourinary involvement
Human Disease
Human Disease
•
Neurological
− Depression, mental fatigue
•
Cardiovascular
− Endocarditis resulting in death
•
Chronic brucellosis is hard to define
− Length, type and response to treatment
variable
− Localized infection
•
Blood donations of infected should
Diagnosis in Humans
Diagnosis in Humans
•
Isolation of organism
− Blood, bone marrow, other tissues
•
Serum agglutination test
− Four-fold or greater rise in titer − Samples 2 weeks apart
•
Immunofluorescence of organism in
clinical specimen
Treatment of Choice
Treatment of Choice
•
Combination therapy has the best
efficacy
− Doxycycline for six weeks in
combination with streptomycin for 2-3 weeks or rifampin for 6 weeks
•
CNS cases treat 6-9 months
− Same for endocarditis cases plus
Prognosis
Prognosis
•
May last days, months or years
•Recovery is common
•
About 5% of treated cases relapse
Failure to complete the treatment regimen Sequestered infection requiring surgical
drainage
•