CRISPR Typing and Subtyping for Improved Laboratory Surveillance of Salmonella Infections

Laboratory surveillance systems for salmonellosis should ideally be based on the rapid serotyping and subtyping of isolates. However, current typing methods are limited in both speed and precision. Using 783 strains and isolates belonging to 130 serotypes, we show here that a new family of DNA repeats named CRISPR (clustered regularly interspaced short palindromic repeats) is highly polymorphic in Salmonella. We found that CRISPR polymorphism was strongly correlated with both serotype and multilocus sequence type. Furthermore, spacer microevolution discriminated between subtypes within prevalent serotypes, making it possible to carry out typing and subtyping in a single step. We developed a high-throughput subtyping assay for the most prevalent serotype, Typhimurium. An open web-accessible database was set up, providing a serotype/spacer dictionary and an international tool for strain tracking based on this innovative, powerful typing and subtyping tool

Foodborne pathogens and host predilection

During food manufacturing, the potential exists for contamination of products with pathogenic microorganisms. While the ingestion of a bacterial pathogen will typically result in illness in a susceptible host, it is not the case for each strain within a given species. Pathogenic bacteria display various levels of host specificity: some infect a wide range of hosts, while others have strict host selectivity and are obligate pathogens. Host specificity of bacterial pathogens is determined by multiple molecular interactions between both the pathogens and their hosts. Understanding these interactions in detail will allow risk-based decisions to be made on affected foods, informed by knowledge of specific strains or pathotypes. This has the potential to avoid costly and unnecessary recalls with classical pathogens that can be proved to have a low potential for causing illness