Brucella

Brucella
Scientific classification
Kingdom: Bacteria Phylum: Proteobacteria Class: Alpha Proteobacteria Order: Rhizobiales Family: Brucellaceae Genus: Brucella
Species
B. abortus B. canis B. melitensis B. neotomae B. ovis B. suis

WikiDoc Resources for Brucella
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Evidence Based Medicine
Cochrane Collaboration on Brucella Bandolier on Brucella TRIP on Brucella
Clinical Trials
Ongoing Trials on Brucella at Clinical Trials.gov Trial results on Brucella Clinical Trials on Brucella at Google
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Definitions of Brucella
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List of terms related to Brucella

Overview

Brucella is a genus of Gram-negative bacteria. They are small (0.5 to 0.7 by 0.6 to 1.5 µm), non-motile, encapsulated coccobacilli.

Brucella is the cause of brucellosis, a true zoonotic disease (i.e. human-to-human transmission has not been identified). It is transmitted by ingesting infected food, direct contact with an infected animal, or inhalation of aerosols. Minimum infectious exposure is between 10 - 100 organisms. Brucellosis primarily occurs through occupational exposure (e.g. exposure to cattle, sheep, pigs), but also by consumption of unpasteurised milk products.

There are a few different species of Brucella, each with a slightly different presentation, such as B. melitensis, B. abortus, B. suis and B. citicosis.

Laboratory isolation

Brucella are slow-growing, but may be isolated from normal blood cultures using standard media. In traditional blood culture media, prolonged incubation (up to 6 weeks) may be required, but on modern automated machines the cultures often come positive within seven days. On Gram stain they appear as dense clumps of Gram-negative coccobacilli and are exceedingly difficult to see.

Laboratory acquired brucellosis is common. This most often happens when the disease is not thought of until cultures become positive, by which time the specimens have already been handled by a number of laboratory staff. The idea of preventative treatment is to stop people who have been exposed to Brucella from becoming unwell with the disease.

There are no clinical trials to be relied on as a guide for optimal treatment, but a three week course of rifampicin and doxycycline twice daily is the combination most often used, and appears to be efficacious; the advantage of this regimen is that it can be taken by mouth and there are no injections, however, a high rate of side effects (nausea, vomiting, loss of appetite) has also been reported.

Blue light study

In a study published in Science magazine in August of 2007, it was revealed that Brucella reacts strongly to the presence of the blue spectrum in natural light, reproducing at a great rate and becoming infectious. Conversely, depriving Brucella of the blue wavelengths dropped its reproductive rate by 90%, a result one of the co-authors called "spectacular."

Treatment

• 1.Uncomplicated brucellosis in adults and children eight years of age and older

• Preferred regimen: Doxycycline 100 mg PO bid for 6 weeks AND Streptomycin 1 g/day IM for 2-3 weeks
• Alternative regimen (1): Doxycycline 100 mg/day PO for six weeks ANDGentamicin 5mg/kg IM for 7-days
• Alternative regimen (2): Gentamicin 5mg/kg/dayIV/ IM for 7-10 days AND Rifampicin 600–900 mg/day PO for six weeks

• 2.Complications of brucellosis

• 2.1Spondylitis

• Preferred regimen:Doxycycline for 3 months AND Streptomycin for 2 to 3 weeks.

• 2.2 Neurobrucellosis

• Preferred regimen: Ceftriaxone 2 mg IV bid for 1 month AND Doxycycline 100 mg PO bid for 4-5 month AND Rifampicin 600–900 mg/day PO for 4-5 month

• 2.3 Brucella endocarditis

• Preferred regimen: Doxycycline AND an Aminoglycoside for at least 8 weeks, and therapy should be continued for several weeks after surgery when valve replacement is necessary
• NOTE: Rifampicin OR Trimethoprim/sulfamethoxazole are used for their ability to penetrate cell membranes

• 3. Pregnancy
• Preferred regimen:Rifampin 900 mg PO qd for 6 weeks

• NOTE: Adding Trimethoprim-sulfamethoxazole can be considered, but this option should probably be avoided preceding the 13th week and after the 36th week of gestation because of concern about teratogenicity and kernicterus Co-trimoxazole has been used in individual cases with reported success.

• 4.For children < eight years of age

• Preferred regimen: TMP/SMZ 8/40 mg/ kg/day bid PO for 6 weeks AND Streptomycin 30 mg/kg/day IM qd for 3 weeks OR Gentamicin 5 mg/kg/day IM/ IV qd for 7-10 days
• Alternative regimen (1): TMP/SMZ AND Rifampicin 15 mg/kg/day PO for 6 weeks
• Alternative regimen (2): Rifampicin AND an Aminoglycoside

External links

• Brucellosis

• Brucella Genome Projects (from Genomes OnLine Database)

• Comparative Analysis of Brucella Genomes (at DOE's IMG system)

• Brucella Bioinformatics Portal