I am working on salmonella from poultry origin with respect to genotype and virulence characterisation. I want to justify the work undertaken with respect to virulence genes. Why there is need to detect them what is the distribution of virulence genes on different pathogenicity loci.
This is largely dependent on what you are looking for. If this is virulence in humans then there are a large number of genes involved. It is difficult to predict how virulent something is from gene content alone-this tells us nothing of expression in relevant environments.
The biggest problem with a virulotyping approach is that most Salmonella have most 'virulence genes' and variation is not that great. The SPI1 effector sopE is one that varies and human 'epidemic' strains typically have this gene.
If you are interested in virulence in poultry-especiialy S. Gallinarum, then there are some important additions-notably the SPI19 encoded secretion system. But in general as Salmonella is quite a clonal beast, but predicting variation in virulence from genotype alone is hard to do.
I think you can justify investigating virulence genes in two ways:
(1) Poultry strains of Salmonella can easily become the source of human infections, so it's worth investigating virulence genes from the public health perspective.
(2) Many virulence genes code for functions that are biologically adaptive for the bacterium that carries them - such as adherence and iron scavenging and only coincidentally contribute to pathogenicity.
Thus you can argue that by investigating virulence genes you are investigating how the bacterias' environment is shaping them and impacting their human pathogenicity.
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