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BACTERIOLOGY
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MicroBioNet Your Microbiology Universe on the Internet |
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GRAM
NEGATIVE
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FAMILIES
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| Acetobacteriaceae |
| Alcaligenaceae |
| Bacteroidaceae |
| Chromatiaceae |
| Enterobacteriaceae |
| Legionellaceae |
| Neisseriaceae |
| Nitrobacteriaceae |
| Pseudomonadaceae |
| Rhizobiaceae |
| Rickettsiaceae |
| Spirochaetaceae |
| Vibrionaceae |
| Genera of Unestablished Relationships |
| Brucella |
| Chromobacterium |
| Brucella abortus |
| CLASSIFICATION | VIRULENCE FACTORS | ENVIRONMENTAL |
| BIOCHEMISTRY | NORMAL FLORA | INDUSTRIAL USES |
| GENETICS | PATHOGENS | VACCINES |
| SEROLOGY | LABORATORY ID |
Brucella abortus is subdivided into a number of biovars. The biovars are separated on the basis of CO2 requirement, production of H2S, growth in the presence 20µg/ml basic fuchsin and in various concentrations thionin and thionin blue. The monospecific antigens of B. abortus (antigen 'A') and B. melitensis (antigen 'M') are distributed to varying extents among the different biovars. Thus their reactions in these monospecific B. abortus (A) or monospecific B. melitensis (M) can also used to differentiate biovars.
Brucella abortus is not pigmented. Acid is not produced from glucose. D-Glucose and D-galactose can be oxidatively assimilated as can i-erythritol and the amino acids L-alanine, L-asparagine and L-glutamic acid. Some biovars require CO2, some produce H2S, they all produce urease within two hours and most can grow in the presence 20µg/ml basic fuchsin.
These organisms have not been shown to carry any naturally occurring plasmids, but transfer of Escherichia coli plasmids has been achieved in the laboratory. Phage transduction (the transfer of genetic information mediated by phages) has been achieved. There are also phage-typing schemes available.
The monospecific antigens of B. abortus (antigen 'A') and B. melitensis (antigen 'M') are distributed to varying extents among the different biovars. Agglutination of thick suspensions in 5% phenolised saline, heated to 60°C for an hour using monospecific B. abortus (A) or monospecific B. melitensis (M) is used to differentiate strains. Generally strains are agglutinated only by A or M antiserum.
Strains of Brucella are able to survive within cells, where they are protected from serum antibody and antibiotics. They can survive in macrophages for months. Erythritol, which is found in some mammalian placentas, such as cattle encourages the growth of B. abortus, hence contagious abortion of cattle.
It is not part of the normal flora. It may be carried by animals including some wild-life.
They are specific pathogens of cattle in which they cause contagious abortion and humans in whom they cause undulent fever.
To isolate strains of
B. abortus multiple blood cultures have to be taken. These have to
be incubated under 10% CO2, at 35°C for up to six weeks. Special rich media,
including serum, blood or haemin have to be used. Similar techniques are
reqired to isolate the strains from other human or animal sources. Strong
biosafety measures should be applied, at least containment level 3.
Not normally found in soil or water but may be found near aborted cattle foetuses.
Apart from the production of antigens for diagnostic kits there are no industrial uses.
Low virulence live vaccines
prepared from B. abortus strain 19 are frequently used to vaccinate
cattle.
Adjuvant killed
whole cell vaccines are also sometimes used.
There are also experimental
human vaccines using fractions from killed preparations.
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