Campylobacter and Salmonella in poultry and poultry products: hows and whys of molecular typing

Abstract

Molecular typing can help to manage and contain food-borne pathogen contamination in poultry and poultry products by providing a means to accurately evaluate sources and transmission routes of specific strains. Moreover, it provides an opportunity to identify the virulence determinant genes characterising the poultry strains that may cause human diseases.

This paper summarises the main applications of genotyping methods in the epidemiological investigations of Campylobacter and Salmonella, in order to identify clonally related and sporadic strains as well as to keep track of the geographical spread and prevalence shifts of epidemic and endemic clones.

Moreover, examples of applications of comparative genomics, by whole genome sequencing and microarray, are given in order to demonstrate how to investigate the difference in virulence determinant genes among Salmonella poultry strains and to distinguish different genotypes among Campylobacter strains. Although virulence determinants have been defined for Escherichia coli and Salmonella enterica, despite use of molecular typing and virulence assays for many years, virulence determinant genes have not been identified for Campylobacter. Putative virulence genes, such as cdt, have been discovered, but for the majority a clear role in disease causation has not been established. It is unlikely that comparative molecular typing using the methods available to a single laboratory will elucidate the virulence mechanisms and associated determinants. It is also, therefore, not yet possible to investigate differences in virulence gene complement for Campylobacter by genome sequencing and microarray in the same way as has been described for E. coli and S. enterica.

Keywords::

• Campylobacter
• Salmonella
• poultry strains
• epidemiology
• pathogenicity