Question Could assessment of purchase behaviour h Essays - Bacteria

Question: Could assessment of purchase behaviour help to identify the contaminated food commodity? Introduction to the case Most cases occurred in elderly males. June 2009 to January 2010 Signicance of the case The main route of transmission is known to be through consumption of contaminated food. However, infection can also (in very rare cases) be transmitted directly from infected animals to humans. The bacterium is particularly successful in causing foodborne disease, because it survives food processing technologies that rely on acidic or salty conditions, and, unlike many other pathogens, can continue to multiply slowly at low temperatures, allowing growth even in properly refrigerated foods Regulatory aspects -EU Directive 2073/2005. -Regulation states that L. monocytogenes must be absent from food, but can be present up to a limit of 100 CFU/g if the physicochemical prole of a food commodity prevents growth (the bacteria must not exceed 100 CFU/g food at the end of shelf-life; Anonymous, 2006). Since listeriosis is usually caused by a higher number of L. monocytogenes (10 5 CFU/g), the search began for a food item that fosters growth and that is predominantly eaten by elderly persons. smoked sh products, soft cheeses and cooked sausages What made outbreak investigations difcult? incubation period of listeriosis in humans can be up to 70 days, the outbreak pattern is quite scattered foodstuffs have usually been eaten or already thrown away before an outbreak investigation starts. -Collected grocery receipts of purchases made by seven patients in December 2009, and screened them for a common food item. -The survey of the purchase behaviour allowed us to generate a hypothesis that was then tested by a case-control study using case-case comparisons. - Patients were asked about consumption of 12 cheese products in the six-month period prior to disease onset. - Persons in the control group were requested to provide information on consumption of the same products and a parameter called the odds ratio' was computed Resolution and outcomes Clinical dynamics -Median age of the cases was 72 years (range: 57-89 years), and 26 patients were male. There were no materno-neonatal(-) cases. Prevalence of underlying disease in the case group was not different from the prevalence of underlying disease in the control group. Contamination rates of samples and recalled lots of Quargel Three out of 16 L. monocytogenes positive lots showed a contamination rate of 100 CFU/g at the beginning of the shelf-life when stored at 4 C. Nevertheless, by increasing the storage time or the storage temperature (15 C, 22 C) the contamination rate could be raised to 10. In general, storage at 4 C resulted in an average of 5.6 log units, a signicantly minor contamination rate compared with storage at 15 C or 22 C with mean log values of 7.2 and 6.8, respectively. Lower storage temperatures are supposed to slow down bacterial growth and may restrict amounts to non-harmful doses. This was not the case in this outbreak. Although there was an overall higher variation in the samples stored at 4 C than in samples kept at 15 C or 22 C, and even though the mean values differed signicantly, maximum levels were similar. This nding indicates a high potential for growth even when Quargel is stored at 4 C At-site contamination scenarios An environmental L. monocytogenes 1/2a isolate from the suspect production plant, from a gully (drainage pit) sample collected in December 2009, became available on 19 January 2010 and proved indistinguishable from the outbreak strain by genotyping. Commentary and personal reections -majority of outbreak investigations do not found the source. - The outbreak dynamics show clearly that a decline in case numbers does not necessarily imply that the underlying problem has disappeared. - a L. monocytogenes isolate from an environmental sample taken by the quality manager in the facility in May 2009 was the rst evidence of a contamination problem. - We hypothesize that L. monocytogenes was introduced into the plant during major construction work. -From 23 February 2009 until 27 May 2009, a ripening room in direct proximity to the central production facility was remodeled, and this coincides with the time of the rst documented detection of L. monocytogenes in a smear sample, allegedly after years of no microbiological proof of L. monocytogenes in the facility. - This nding emphasizes the unequivocal need for implementing a self-control system capable of detecting contamination -This strong recommendation becomes