Good Farm Hygiene Can Reduce Listeria in Pork

FINLAND - Listeria monocytogenes contamination in pork can originate on the farm, according to researchers, and so good practices there can help to reduce this food-borne infection. The prevalence was significantly higher in organic than in conventional pig production.
calendar icon 7 April 2010
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S. Hellströ of the University of Helsinki and co-authors at the Finnish Food Safety Authority Evira and EFSA have investigated the source of Listeria monocytogenes contamination in pork. Their paper, published in the current issue of Journal of Food Protection, suggests that contamination may start on the farm.

The presence of L. monocytogenes in the pork production chain was followed from farm to slaughterhouse by examining the farm and slaughterhouse levels in the same 364 pigs, and finally by analysing the cut meats from the same pig lots. Both organic and conventional farms were included in the study. Altogether, 1,962 samples were collected, and the 424 L. monocytogenes isolates were analysed by pulsed-field gel electrophoresis.

The results from microbial analyses were combined with data from an on-farm observation and a questionnaire to clarify the associations between farm factors and prevalence of L. monocytogenes.

The prevalence of L. monocytogenes was 11, one, one, 24, five, one and four per cent, respectively in feed and litter, rectal swabs, intestinal contents, tonsils, pluck sets (including lungs, heart, liver, and kidney), carcasses and meat cuts.

The prevalence was significantly higher in organic than in conventional pig production at the farm and slaughterhouse level, but not in meat cuts.

Similar L. monocytogenes genotypes were recovered in different steps of the production chain in pigs originating from the same farm.

Specific farm management factors, i.e. large group size, contact with pet and pest animals, manure treatment, use of coarse feed, access to outdoor area, hygiene practices and drinking from the trough, influenced the presence of L. monocytogenes in pigs.

Hellströ and co-authors concluded that L. monocytogenes is present in the production chain, and transmission of the pathogen is possible throughout the chain, from the farm to pork. Good farm-level practices can reduce the prevalence of this pathogen.


Hellströ, S., R. Laukkanen, K-M. Siekkinen, J. Ranta, R. Maijala and H. Riitta. 2010. Listeria monocytogenes contamination in pork can originate from farms. Journal of Food Protection, 73 (4): 641-648.

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