There is a zero tolerance policy for Listeria monocytogenes in ready-to-eat products and for Escherichia coli O157:H7 in non-intact fresh beef products; thus, appropriate methods must have the ability to detect one colony forming unit in the sample being analyzed after enrichment culturing. Regardless of the technology employed, food analysis remains a challenging task Problems that complicate pathogen detection include: (1) non-uniform distribution of pathogens in the food, thus the sample analyzed may not be representative of the entire lot; (2) low level of the target pathogen compared to that of the indigenous microbiota, which may be present at levels as high as 108 CFU/g in raw products; (3) heterogeneity of food matrices and food components interfering with growth or detection of the target organism; and (4) inability to recover injured target organisms using selective enrichment media.
One of the exciting developments in food microbiology has been the availability and application of molecular analyses that have allowed scientists to address microbial food safety questions beyond merely determining whether particular pathogens are in a food. Such global analyses are allowing scientists to ask deeper questions regarding food-borne pathogens and are currently leading the way to ascertaining the genes, proteins, networks, and cellular mechanisms that determine the persistence of strains in foods and other environments, determine why certain strains are more commonly isolated from foods, and determine why certain strains are more pathogenic. Such molecular tools are also making it possible to more fully determine the microflora present in foods along with pathogens, and to assess the effect that the food microbiota has on the death, survival, and pathogenicity of food borne pathogens. As the application of molecular analyses improves our understanding of the responses of pathogens to foods and food environments, we anticipate that the information will lead to the development of more specific detection tests, will lead to the enhancement of current interventions, and will lead to the development of new interventions.