| 1. |
- Artursson, Karin, et al.
(author)
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Foodborne pathogens in unpasteurized milk in Sweden
- 2018
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In: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 284, s. 120-127
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Journal article (peer-reviewed)abstract
- Raw milk may be a risk for public health if it is contaminated with zoonotic pathogens. To study the prevalencein unpasteurized milk from Swedish farms, bovine and small ruminant dairy farms were sampled. Since thesampling method and transport conditions may influence the outcome of analyses, efforts were made to optimizethe methodology. Culturing of bacteria was done from in-line milk filters collected from the milk pipe at thepoint where it enters the milk bulk tank at the farms and this way of sampling was compared to sampling bulktank milk (BTM) directly. Analysing milk filters were found to be superior to analysing BTM directly. Conditionsfor transport of milk filter samples were further improved by the addition of Cary Blair transport medium, whichsignificantly increased the number of positive samples for pathogenic bacteria. The isolation of several foodbornepathogens from milk filters was demonstrated. The prevalence of samples with Staphylococcus aureus was71% and 64%, and Listeria spp. 21% and 29% from dairy cow and goat/sheep farms, respectively. Campylobacterjejuni, Yersinia enterocolitica and verotoxigenic Escherichia coli (VTEC) O157 were detected in 9%, 2% and 2% ofsamples from bovine milk, respectively.We conclude that the choice of sampling method and sample handling influence the results of bacterialculturing. From the results of this study, we strongly recommend to sample in-line milk filters instead of BTMdirectly and to use Cary Blair medium during transport, especially if the samples are to be analysed forCampylobacter spp. and/or Listeria spp. The findings also show that unpasteurized milk from Swedish farmsoccasionally contain bacteria with zoonotic potential.
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| 2. |
- Nilsson, Anders, et al.
(author)
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Detection of Yersinia enterocolitica in food by PCR amplification
- 1998
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In: Letters in Applied Microbiology. - Oxon, United Kingdom : Blackwell Publishing. - 0266-8254 .- 1472-765X. ; 26, s. 140-144
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Journal article (peer-reviewed)abstract
- A polymerase chain reaction (PCR) assay was developed for detection ofpathogenic, virulent strains of Yersinia enterocolitica. By using both virulence loci virFand ail as markers for pathogenicity, detection of species with a virulence factor present waspossible. DNA preparation in the presence of hexadecyl trimethy ammonium bromide(CTAB) was followed by two 44 cycle amplification reactions, one for each of themarkers. As few as 102Y. enterocolitica cells were detected in ground pork in thepresence of 105–106bacteria of other species. The described PCR assay providesa sensitive robust assay for the detection of virulent Y. enterocolitica in food.
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| 5. |
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| 6. |
- Söderqvist, Karin, et al.
(author)
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Fate of Listeria monocytogenes, Pathogenic Yersinia enterocolitica, and Escherichia coli O157:H7 gfpþ in Ready-to-Eat Salad during Cold Storage: What Is the Risk to Consumers?
- 2017
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In: Journal of Food Protection. - 0362-028X. ; 80, s. 204-212
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Journal article (peer-reviewed)abstract
- In this study, we investigated the fate of Listeria monocytogenes, pathogenic Yersinia enterocolitica, and Escherichia coli O157:H7 gfp(+) inoculated in low numbers into ready-to-eat baby spinach and mixed-ingredient salad (baby spinach with chicken meat). Samples were stored at recommended maximum refrigerator temperature (8 degrees C in Sweden) or at an abuse temperature (15 degrees C) for up to 7 days. Mixed-ingredient salad supported considerable growth when stored at 15 degrees C during shelf life (3 days), with populations of L. monocytogenes, pathogenic Y. enterocolitica, and E. coli O157:H7 gfp(+) increasing from less than 2.0 log CFU/g on day 0 to 7.0, 4.0, and 5.6 log CFU/g, respectively. However, when mixed-ingredient salad was stored at 8 degrees C during shelf life, only L. monocytogenes increased significantly, reaching 3.0 log CFU/g within 3 days. In plain baby spinach, only pathogenic Y. enterocolitica populations increased significantly during storage for 7 days, and this was exclusively at an abuse temperature (15 degrees C). Thus, mixing ready-to-eat leafy vegetables with chicken meat strongly influenced levels of inoculated strains during storage. To explore the food safety implications of these findings, bacterial numbers were translated into risks of infection by modeling. The risk of listeriosis (measured as probability of infection) was 16 times higher when consuming a mixed ingredient salad stored at 8 degrees C at the end of shelf life, or 200,000 times higher when stored at 15 degrees C, compared with when consuming it on the day of inoculation. This indicates that efforts should focus on preventing temperature abuse during storage to mitigate the risk of listeriosis. The storage conditions recommended for mixed-ingredient salads in Sweden (maximum 8 degrees C for 3 days) did not prevent growth of L. monocytogenes in baby spinach mixed with chicken meat. Manufacturers preparing these salads should be aware of this, and recommended storage temperature should be revised downwards to reduce the risk of foodborne disease.
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| 7. |
- Söderqvist, Karin, et al.
(author)
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Foodborne Bacterial Pathogens in Retail Prepacked Ready-to-Eat Mixed Ingredient Salads
- 2016
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In: Journal of Food Protection. - 0362-028X. ; 79, s. 978–985-
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Journal article (peer-reviewed)abstract
- Pre-packed ready-to-eat mixed ingredient salads (RTE salads) are readily available whole meals that include a variety of ingredients such as raw vegetables, cooked meat, and pasta. As part of a trend toward healthy convenience foods, RTE salads have become an increasingly popular product among consumers. However, data on the incidence of foodborne pathogens in RTE salads are scarce. In this study, the microbiological safety of 141 RTE salads containing chicken, ham, or smoked salmon was investigated. Salad samples were collected at retail and analyzed using standard methods for Listeria monocytogenes, Shiga toxin-producing Escherichia coli (STEC), pathogenic Yersinia enterocolitica, Salmonella, and Campylobacter spp. L. monocytogenes was isolated from two (1.4%) of the RTE salad samples. Seven (5.0%) of the samples were positive for the ail-gene (present in all human pathogenic Y. enterocolitica) and three (2.1%) of the samples were positive for the Shiga toxin-genes stx1 and/or stx2. However, no strains of pathogenic Y. enterocolitica or STEC were isolated. Thus, pathogens were found or suspected in almost 1 of 10 RTE salads investigated, and pathogenic bacteria probably are present in various RTE salads from retail premises in Sweden. Because RTE salads are intended to be consumed without heat treatment, control of the ingredients and production hygiene is essential to maintain consumer safety. The recommended maximum storage temperature for RTE salads varies among countries but can be up to 8 °C (e.g., in Sweden). Even during a short shelf life (3 to 5 days), storage at 8 °C can enable growth of psychrotrophs such as L. monocytogenes and Y. enterocolitica. The maximum storage temperature should therefore be reduced.
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| 8. |
- Thelaus, Johanna, et al.
(author)
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Network Experiences from a Cross-Sector Biosafety Level-3 Laboratory Collaboration : A Swedish Forum for Biopreparedness Diagnostics
- 2017
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In: Health Security. - : Mary Ann Liebert. - 2326-5094 .- 2326-5108. ; 15:4, s. 384-391
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Journal article (peer-reviewed)abstract
- The Swedish Forum for Biopreparedness Diagnostics (FBD) is a network that fosters collaboration among the 4 agencies with responsibility for the laboratory diagnostics of high-consequence pathogens, covering animal health and feed safety, food safety, public health and biodefense, and security. The aim of the network is to strengthen capabilities and capacities for diagnostics at the national biosafety level-3 (BSL-3) laboratories to improve Sweden's biopreparedness, in line with recommendations from the EU and WHO. Since forming in 2007, the FBD network has contributed to the harmonization of diagnostic methods, equipment, quality assurance protocols, and biosafety practices among the national BSL-3 laboratories. Lessons learned from the network include: (1) conducting joint projects with activities such as method development and validation, ring trials, exercises, and audits has helped to build trust and improve communication among participating agencies; (2) rotating the presidency of the network steering committee has fostered trust and commitment from all agencies involved; and (3) planning for the implementation of project outcomes is important to maintain gained competencies in the agencies over time. Contacts have now been established with national agencies of the other Nordic countries, with an aim to expanding the collaboration, broadening the network, finding synergies in new areas, strengthening the ability to share resources, and consolidating long-term financing in the context of harmonized European biopreparedness.
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| 9. |
- Thisted Lambertz, Susanne, et al.
(author)
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A combined culture and PCR method for detection of pathogenic Yersinia enterocolitica in food
- 2000
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In: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 57:1-2, s. 63-73
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Journal article (peer-reviewed)abstract
- A combined method based on traditional culturing, buoyant density centrifugation, (BDC), and polymerase chain reaction (PCR) techniques for detection and identification of pathogenic Y. enterocolitica in food was developed and evaluated. An internal control, which was added in each PCR-tube and co-amplified by the same primer pair as the pathogen, monitored false-negative PCR results. The sample preparation step, BDC, was used to remove PCR inhibiting food substances and to concentrate the Y. enterocolitica cells. Single PCR with a chromosomal gene (ail) as target was chosen for screening the samples. The method was tested on naturally and artificially contaminated food samples. In three different food samples, processed meat (brawn), unprocessed beef and minced pork, inoculated with 10 cfu pathogenic Y. enterocolitica per gram, Y. enterocolitica was detected and cultural bacteria indicated within 18 h of enrichment.
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| 10. |
- Thisted Lambertz, Susanne, et al.
(author)
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A comparison between a PCR method and a conventional culture method for detecting pathogenic Yersinia enterocolitica in food
- 1996
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In: Journal of Applied Bacteriology. - : Blackwell Publishing. - 0021-8847. ; 81:3, s. 303-308
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Journal article (peer-reviewed)abstract
- The aim of this study was to develop a polymerase chain reaction (PCR) method for the detection of pathogenic Yersinia enterocolitica and to compare it with an official culture method (NMKL-117). Primers were selected for nested PCR directed at the attachment invasion locus, ail, on the bacterial chromosome, as well as at a sequence on the pathogenic marker plasmid, termed virulence factor, virF. The final results obtained by the two methods were similar. However, while the conventional method yielded contradictory data for some steps the PCR method provided unambiguous results. Considerable advantages, i.e. higher sensitivity and specificity of the PCR method, compared with the conventional method for detecting pathogenic Y. enterocolitica, were demonstrated in this study.
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