Campylobacter detection along the food chain--towards improved quantitative risk analysis by live/dead discriminatory culture-independent methods.

Death, although absolute in its consequence, is not measurable by an absolute parameter in bacteria. Viability assays address different aspects of life, e. g. the capability to form a colony on an agar plate (CFU), metabolic properties or mem- brane integrity. For food safety, presence of infectious potential is the relevant criterion for risk assessment, currently only partly reflected by the quantification of CFU. It will be necessary for future improved risk assessment, in particular when fastidious bacterial pathogens are implicated, to enhance the informative value of CFU. This might be feasible by quantification of the number of intact and potentially infectious Campylobacter, impermeable to the DNA intercalating dye propidium monoazide (PMA). The latter are quantifiable by the combination of PMA with real-time PCR, although thorough controls have to be developed for standardization and the circumvention of pitfalls. Under consideration of differ- ent physiological states of the food-borne pathogen, we provide an overview of current and future suitable detection/quantification targets along the food chain, including putative limitations of detection.