059-067 Gram

Introduction Listeriosis is a food-borne disease which primarily affects people in particular risk-groups (immuno-suppressed, elderly, neonates) in which lethality is as high as 25%. The disease does occur in out-breaks but most cases appear as sporadic cases. The disease is primarily associated with ready-to-eat (RTE) food products with extended (refrigerated) shelf life. Outbreaks have mostly been caused by dairy and meat products, however, the disease has also been traced to lightly-preserved fish products such as smoked mussels and cold-smoked fish (trout). Determining infectious dose is difficult due to lack of good animal infection models and the risk associated with different doses of the organism has therefore been evaluated by comparing disease rates with prevalence with models of growth of the organism (1). The quantitative risk assessments conducted by FDA/FSIS (2) and WHO/FAO (3) have used a similar approach and have also compared a range of dose response curves from different studies. Using such approaches, all studies conclude that the risk of listeriosis is higher when consuming food products with high numbers of the organism than when consuming food products with low levels (figure 1 (3)). However, a minimum infectious dose cannot be determined. The WHO/FAO team concluded as part of an expert consultation that 99% of all listeriosis cases would be eliminated if levels of L. monocytogenes (L.m.) were kept below 1000 cfu L.m./g at point of consumption assuming a consumption pattern equivalent to that of the USA.