Taking Forward Molecular Approaches for Detection and Typing of Brucella

Brucellosis remains a serious disease problem in many parts of the world affecting both animals and man. The UK is currently free of the causative organisms of brucellosis, the Brucella species, but there remains a substantial risk of importation into the UK as illustrated by the occurence of three distinct outbreaks of disease in the last three years. In order to ensure that the UK remains Brucellosis free an extensive surveillance program is undertaken involving the frequent testing of resident herds and of animals imported into the UK. <P>

The aim of this research is to support this surveillance effort by developing improved tools to detect Brucella spp. rapidly and cheaply and improved methods to distinguish between strains of Brucella that will help in efforts to identify the source of an infection. Work undertaken in this project will assist these goals in a number of ways. Tests will be developed and validated that detect the genetic material of the Brucella bacterium directly in clinical material. This will facilitate quicker detection of the organism than current approaches that are dependent on growing the bacterium - a process that can take days or weeks.

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In order to support this work and improve the cultural techniques we will characterise organisms that resemble, and thus can be confused with, Brucella. Characterisation of these organisms will allow their use in studies to develop improved selective media for Brucella culture and in ensuring they do not cross-react in diagnostic tests. A large portion of this project will involve the development of improved typing tools in support of our reference and surveillance functions. Current identification of distinct Brucella species is based on subtle differences in the metabolism and chemical structure between species - this approach is time-consuming, culture dependent, expensive and acknowledged to be rather subjective. We will develop an alternative approach to undertake this identication by characterising the genetic make-up of stable regions of the genomes from a representative sample of the Brucella population. This will allow the identification of unambiguous single genetic changes that define each of the species and that can be used to develop a multiplex, culture-independent and objective assay to identify the distinct Brucella species. The assay will also be further developed to address other issues that are important in our reference functions (such as further differentiation of the species into `biovars` and the identification of vaccine strains) by identifying specific changes that characterise these groups and can be added to the assay. The outcome will be a rapid, straightforward and unambiguous assay that can provide information in a single test equivalent to that currently dependent on a variety of cultural and genetic tests. <P>
Further work will involve the development of techniques, reliant on less stable regions of the genome, that provide much more detailed discrimination between isolates. These tests promise to be invaluable in supporting and/or directing conventional approaches used to identify the source of a Brucella outbreak as well as providing general support to our reference functions by facilitating a much more detailed understanding of the diversity and distribution of Brucella strains worldwide. The advantages of the new approaches will be publicised by undertaking comparative studies of old and new methods to compare the power and versatility of the techniques and ensuring this information is in the public domain.