Prevalence and level of Listeria monocytogenes in ready-to-eat foods in Sweden 2010

An increasing trend in human listeriosis cases over the past five years (2005–2009) in Sweden encouraged the authorities to examine the prevalence and levels of Listeria monocytogenes in ready-to-eat (RTE) foods in 2010. The combined results of two surveys are presented: the Swedish part of an EU-wide survey and a national survey. A total of 1590 samples covering three categories of RTE food able to support growth of L. monocytogenes: (i) soft and semi-soft cheeses (mould- and smear-ripened); (ii) heat-treated meat products; and (iii) smoked and gravad fish, were collected at retail outlets and analysed at the end of shelf life. L. monocytogenes was detected in 0.4% of 525 cheese samples, 1.2% of 507 meat-product samples and 12% of 558 fish samples. In the latter category, L. monocytogenes was found in 14% of both gravad and cold-smoked fish samples and in approximately 2% of hot-smoked fish samples. The percentage of cold-smoked or gravad fish testing positive for L. monocytogenes was significantly lower in samples processed in Sweden (8%) than in samples processed in other countries (45%). Levels of L. monocytogenes exceeding 100 cfu/g were found in one (0.2%) of the cheese samples and in three (0.5%) of the fish samples. The high prevalence of contaminated cold-smoked and gravad fish samples suggests that these products constitute the main problem. This has induced the development of a national strategy plan with the aim to halve the prevalence of L. monocytogenes in cold-smoked and gravad fish at retail in Sweden by the end of year 2015.

► L. monocytogenes was detected in 12% of 558 fish samples.
► 0.2% of the cheese samples and 0.5% of the fish samples exceeded 100 cfu per gram.
► Contamination was lower in fish samples processed in Sweden than other countries.