| 1. |
- Thisted Lambertz, Susanne, et al.
(författare)
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A combined culture and PCR method for detection of pathogenic Yersinia enterocolitica in food
- 2000
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Ingår i: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 57:1-2, s. 63-73
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Artursson, Karin, et al.
(författare)
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Foodborne pathogens in unpasteurized milk in Sweden
- 2018
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 284, s. 120-127
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Thisted Lambertz, Susanne, et al.
(författare)
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Subtyping of Listeria monocytogenes isolates recovered from retail ready-to-eat foods, processing plants and listeriosis patients in Sweden 2010
- 2013
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Ingår i: International Journal of Food Microbiology. - Amsterdam, Netherlands : Elsevier. - 0168-1605 .- 1879-3460. ; 166, s. 186-192
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Tidskriftsartikel (refereegranskat)abstract
- Identification and prioritisation of food safety interventions requires an understanding of the relationship be- tween food, pathogens and cases. Such understanding can be gained through different approaches, e.g. microbial subtyping to attribute cases of foodborne disease to food vehicles or other sources of illness. In this study, Listeria monocytogenes isolates (n = 166) from (i) three categories of ready-to-eat (RTE) foods, (ii) food processing plant environments, and (iii) human listeriosis cases, all sampled during 2010 in Sweden, were subtyped. In addition, 121 isolates from human listeriosis cases, collected 2005–2009, were subtyped. Subtyping consisted of both serotyping (conventional method and PCR) and genotyping using pulsed-field gel electrophoresis (PFGE). Serotype 1/2a dominated in all three groups of isolates (range 73–96%). Eighteen percent of the human isolates (2010) belonged to serotype 4b, but only 1.4% of the food isolates. The food isolates differentiated into 19 pulsotypes (ID = 0.843), the human isolates collected 2010 into 31 pulsotypes (ID = 0.950) and the processing plant isolates into 22 pulsotypes (ID = 0.991). Six of the pulsotypes were shared between the food and human isolates. These pulsotypes comprised 42% of the human isolates and 59% of the food isolates. For some processing plants, there was suggested persistence of one or more specific L. monocytogenes strains, as indicated by repetitive isolation of the same pulsotype from food. This study indicated the presence of L. monocytogenes in the processing plant environment as a likely source of contamination of gravad and cold-smoked fish, and this food category as an important source of human exposure to the pathogen
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