Food Protection Trends - February 2009 - 87

SESSION 3: Microbial Hazards: Recently Emerged Pathogens Listeria monocytogenes loNE GrAm, Technical University of Denmark, Danish Institute for Fisheries Research, Soltofts Plads, DTU Bldg. 221, kongens lyngby, Dk-2800, Denmark Listeria monocytogenes is a human foodborne pathogen that has a remarkable ability to colonize food processing environments and the processing environment is often the immediate source of product contamination. Disease is typically caused by food products in which the organism has grown to high numbers and that are consumed by immunocompromised individuals. Control of the organism relies on minimizing product contamination and preventing growth in relevant food procuts. We have found that a particular molecular subtype may colonize independent fish processing plants over many years. We have investigated factors that may influence the remarkable persistance ability of L. monocytogenes including attachment to inert surfaces, tolerance to disinfection and tolerance to drying. Strains of the particular persistent subtypes do not differ systematically from pre-sumed non-persistent subtypes, however, most strains of L. monocytogenes are remarkably tolerant to drying and survive for months if protected by organic material or NaCl. The particular persistent subtypes which are likely contaminants of food products are less invasive in a number of mammalian cell line models. This may be explained by mutations in genes encoding proteins (ActA and IntA) that are important for cell invasion. In an animal model (pregnant guinea pig), the particular persistent strains are highly efficient in crossing the placental barrier, however, it is not known if the placental crossing in guinea pigs is representative of the human pregnant women. Indeed, these strains do not in a PFGE analyses cluster with isolates from clinical cases. However, these particular persistent strains should be regarded as virulent and efffecient cleaning and sanitizing regimes should be used to control the processing plant contamination. Enterobacter sakazakii CArol IVErSEN, Centre for Food Safety, Veterinary Science Building, University College Dublin, Belfield, Dublin 4, Ireland Enterobacter sakazakii is an opportunistic pathogen that can cause meningitis, necrotising enterocolitis, and bacteraemia infants. It was first designated as a species in 1980 by Farmer et al. and several outbreaks in NICUs have been linked to contaminated powdered infant formula. The organism is therefore of concern to infant food manufacturers as well as clinical microbiologists and food safety regulators. In 2008 the taxonomy of E. sakazakii was updated using a polyphasic approach based on extensive geno- and phenotypic evaluations. This resulted in the description of five novel species and the proposal that these be incorporated into a new genus, Cronobacter, which is contaxic with E. sakazakii. The isolation of Cronobacter is complicated by the existence of closely related species, Enterobacter pulveris, E. helveticus and E. turicensis. These species share similar characteristics to Cronobacter and occur in the same ecological niches including infant foods. However, no health risk has been attributed to these organisms. Several culture media as well as molecular assays have been proposed and the development of an EN ISo horizontal standard for detection of Cronobacter is currently ongoing; the AOAC/FDA are also in the process of validating methods for detection of this genus. Molecular typing methods such as PFGE, RAPD, rep-PCR, riobotyping and MLVA can be applied to trace contamination and monitor infant food processing facilities. Although Cronobacter have been primarily associated with infections in infants, several recent reports have highlighted the risk posed in immunocompromised adults, particularly the elderly. Symptoms described in the patients include pneumoniae, sepsis, foot ulcers, wound infections, osteomyletis and splenic abscesses. TSEs: The Changing Picture DANNy mATTHEWS, Veterinary laboratories Agency (retired), New Haw, Addlestone, Surrey, kT15 3NB, United kingdom BSE has dominated global headlines since 1996, influenced more by uncertainty and fears of the unknown than by hard facts. The political drivers to such misrepresentation of data continue, but in most countries affected by BSE the tide has turned. It is clear that measures put in place to prevent infection of cattle have been effective in most affected countries, while in others prevalence is so low that the detection of trends is difficult. Thirty-one countries are now categorised as “controlled” risk, in accordance with OIE rules for trade. Where next? As recognised by the TSE Road Map published by the European Commission, the aim is to reduce, and potentially withdraw, prohibitively expensive protective measures. Withdrawal of measures is not easy, even though the risk reduction afforded is small. The process will therefore be slow, involving scientific consultation and open debate with politicians and consumer representatives. Whether they lead to total removal of protective measures remains in doubt, but many are now superfluous. What of other TSEs, particularly scrapie in small ruminants and chronic wasting disease in cervids? Do they represent a risk to consumers and are rigorous measures to protect consumers justified? Where a disease occurs naturally in the wild, as with CWD, can science deliver means of controlling or eradicating disease? So far there is no evidence that scrapie or CWD represent a risk to consumers. More than 20 years after the discovery of BSE, the debate about “absence of evidence” and “evidence of absence” continues, but drivers to apply BSE-type controls to small ruminants and cervids are muted. In some respects they present much bigger challenges than BSE. FEBRUARY 2009 | FOOD PROTECTION TRENDS 87

Food Protection Trends - February 2009

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