No abstract

The presence of Listeria 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 analyzing 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 analyzed 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, 1, 1, 24, 5, 1, and 4% in feed and litter, rectal swabs, intestinal contents, tonsils, pluck sets (including lungs, heart, liver, and kidney), carcasses, and meat cuts, respectively. 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. L. monocytogenes was present in the production chain, and transmission of the pathogen was possible throughout the chain, from the farm to pork. Good farm-level practices can therefore be utilized to reduce the prevalence of this pathogen.

Aims: To evaluate the prevalence and genetic diversity of Listeria monocytogenes in wild birds and to compare the genotypes with isolates previously collected from foods and food processing environments. Methods and Results: Samples of wild birds' faeces (n = 212) were collected from a municipal landfill site and from urban areas in the Helsinki region and analysed by two-step enrichment and plating onto L. monocytogenes-selective agar. The overall prevalence of L. monocytogenes in bird faeces was 36% (95% CI 30-43%), and prevalence on the landfill site was significantly higher. All isolates were analysed with pulsed-field gel electrophoresis and compared with the L. monocytogenes profiles in an existing collection. Similar pulsotypes were found in birds and in isolates collected along the food chain. Conclusions: Birds commonly carry L. monocytogenes, and strains are frequently similar with those detected in foods and food processing environments. Thus, birds may disseminate L. monocytogenes in nature and may also contaminate foods when entering the food processing environments and outdoor market places. Significance and Impact of the Study: Populations of L. monocytogenes in wild birds and along the food processing chain overlap. Our findings add to the epidemiological data on this significant foodborne pathogen.

While the quality of raw cow milk in Finland is known for its high hygienic standard, with the national average total bacterial count being below 10(4) CFU/mL annually, the prevalence of pathogenic bacteria in Finnish raw milk is underreported. The aim of this study was to determine the occurrence of Listeria monocytogenes, thermophilic Campylobacter spp., Salmonella spp., stx-positive Escherichia coli (STEC), coagulase-positive staphylococci, Yersinia spp., and Bacillus cereus group in raw cow milk samples collected from bulk tanks at 183 Finnish farms. Additionally, the hygienic quality of the milk was studied by determining the total bacterial and E. coli counts. L. monocytogenes was detected in 5.5% of the milk samples, with concentrations varying from <1 to 30 CFU/mL. Thermophilic Campylobacter spp. or Salmonella spp. were not detected in any of the samples. STEC with Shiga toxin-encoding stx2 was detected in 2.7% of the samples. Yersinia enterocolitica was detected in 7.7% of the samples; however, all isolates were negative for ail, suggesting that they were non-pathogenic. Coagulase-positive staphylococci were detected in 34.4% of the samples, with an average concentration of 25 CFU/mL in the positive samples. Members of the B. cereus group were detected in 20.8% of the samples, with an average concentration of 1 CFU/mL in the positive samples. No relationship was detected between E. coli or the total bacterial count and the presence of pathogenic bacteria, which suggests that pathogens can be present also in farms with excellent production hygiene. Although the concentration of pathogenic bacteria in fresh raw milk was mainly relatively low, it should be borne in mind that some of the pathogenic bacteria can survive and multiply at refrigeration temperatures and may cause a disease with a very low infectious dose. Thus, consumption of raw milk and related products poses a potential risk for food poisoning.

The efficacy of water, chlorinated water (100 ppm), peracetic acid solution (0.05%), and commercial citric acid-based produce wash (0.25%) to reduce the population of Listeria monocytogenes on precut lettuce was tested. Samples were inoculated with a mixture of equal amounts of five L. monocytogenes strains at a level of 4.7 log CFU/g, and analyzed on the day of washing and after 3 and 6 days of storage at 6 degrees C. Sanitizer reduced the number of L. monocytogenes at maximum 1.7 log CFU/g and number of L. monocytogenes reached the inoculation level during 6 days of storage. Thus, disinfectants do not eliminate L. monocytogenes on precut lettuce and cannot be solely relied on in producing precut lettuce safely. The inoculated L. monocytogenes strains were recovered at different rates after 6 days of storage; one of these strains was not recovered at all. Thus, strain-specific differences exist in the ability of L. monocytogenes to survive the washing treatments of the lettuce.