Difference between revisions of "Category:Brucella species"

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|pagebody = There are six species of ''Brucella'' bacteria. They are Gram negative coccobacilli that cause important zoonoses worldwide.
 
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===Overview===
 
 
*Important zoonoses worldwide
 
*Cause chronic granulomatous diseases
 
*6 species
 
*Target reproductive organs of certain species
 
*Infected animals act as reservoir of infection
 
*Organisms can remain viable in moist environment for months
 
*Cause undulant fever in humans
 
 
 
===Characteristics===
 
 
*Small, non-moltile, Gram negative coccobacilli
 
*Facultative intracellular pathogens
 
*Modified Ziehl-Neelsen positive - clusters of red coccobacilli on smears
 
*Aerobic and capnophilic
 
*Catalase positive; oxidase and urease positive except for ''Brucella ovis'' 
 
*Some species require enriched media for growth
 
*Non-haemolytic
 
*Smooth colonies of ''B. abortus, B. melitensis'' and ''B. suis'' are small, glistening, blue and translucent after incubation for 3-5 days, and become opaque with age
 
*Rough colonies of ''B. ovis'' and ''B. canis'' are dull, yellow, opaque and friable
 
*Slide agglutination with speicific antisera detect important antigens
 
*''B. abortus'' lysed by specific bacterophages
 
*Oxidative metaboloic rates can differentiate species
 
 
===Pathogenesis and pathogenicity===
 
 
*Brucellae that lack outer membrane LPS (rough colonies) are less virulent than those which possess it
 
*Penetrate nasal, oral or pharyngeal mucosa
 
*Phagocytosed and carried to regional lymph nodes
 
*Smooth organisms survive and multiply in cells of the reticulo-endothelial system
 
*Inhibit lysosome-phagosome fusion
 
*Superoxide dismutase and catalase production may resist oxidative killing
 
*Lymph nodes enlarge (lymphatic and lymphoreticular hyperplasia) and inflammation is induced
 
*Surviving organisms spread to other organs (liver, [[Spleen - Anatomy & Physiology|spleen]], placenta) and cause granulomatous reactions
 
*Eythritol is a growth stimulant and attracts the bacteria to the placenta of cattle, sheep, goats and pigs; also found in mammary gland and epididymis, targets for brucellae
 
*Infection of foetus and abortion
 
*May localise in joints or intervertebral discs in chronic infections
 
 
 
===Clinical disease===
 
 
*Human brucellosis:
 
**Susceptible to ''B. abortus, B. suis, B. melitensis'' and ''B. canis''
 
**Transmission via contact with secretions from infected animals
 
**Routes of infection: skin abrasions, inhalation, ingestion
 
**Unpasteurised milk source of infection
 
**Undulant fever - fluctuating pyrexia, malaise, fatigue, muscle and joint pains, osteomyelitis
 
**Can become chronic
 
**''B melitensis'' and ''B. suis'' cause most severe infections
 
**Antimicrobials
 
 
===Diagnosis===
 
 
*Serological testing of milk (Milk Ring Test) and beef cattle (Rose Bengal Plate Test)
 
*Serological tests detect anti-lipopolysaccharide antibodies
 
*LPS antigen present in virulent as well as some vaccine strains therefore vaccination may confuse serological testing
 
*False positives due to cross-reaction with LPS in other bacteria
 
*Modified Ziehl-Neelson stains reveal organisms in samples from cotyledons, uterine discharge and foetal abomasal contents
 
*PCR for detection in tissue
 
*Brucellin for intradermal testing for ''B. abortus''
 
*Enriched media for isolation
 
*Complement fixation test
 
*Indirect and competitive ELISA
 
*Serum agglutination test
 
*Antiglobulin test
 
 
 
===Control===
 
 
*Test and slaughter program has eradicated bovine brucellosis in the UK
 
*Vaccination of heifers against ''B. abortus'' in endemic regions:
 
**Strain S19, a live attenuated vaccine, stimulating a cell-mediated immune response; vaccination of young animals; interferes with serological testing
 
**45/20 bacterin vaccine less effective
 
**Newer RB51 vaccine has no LPS O-antigen therefore not detected by serological tests and gives good protection
 
*Live attenuated ''Brucella melitensis'' vaccine to protect lambs and kids against ''B. melitensis''
 
 
[[Category:Bacteria]][[Category:Zoonoses]][[Category:Gram_negative_bacteria]]
 
[[Category:Bacteria]][[Category:Zoonoses]][[Category:Gram_negative_bacteria]]
 
[[Category:Coccobacilli]]
 
[[Category:Coccobacilli]]
[[Category:To_Do_-_Bacteria]]
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[[Category:To_Do_-_AimeeHicks]]

Revision as of 11:54, 22 July 2010

Brucella species

There are six species of Brucella bacteria. They are Gram negative coccobacilli that cause important zoonoses worldwide.

Pages in category "Brucella species"

The following 6 pages are in this category, out of 6 total.