| 1. |
- Antonsson, Martin, et al.
(författare)
-
Lactobacillus strains isolated from Danbo cheese as adjunct cultures in a cheese model system.
- 2003
-
Ingår i: International Journal of Food Microbiology. - 0168-1605. ; 85:1-2, s. 159-169
-
Tidskriftsartikel (refereegranskat)abstract
- Isolates of Non-Starter Lactic Acid Bacteria (NSLAB) from six ripened Danbo cheeses of different ages and of different brands were examined. Special emphasis was on the genus Lactobacillus with the aim of investigating their role in cheese maturation. Thirty-three isolates were typed by the PCR-based method, Randomly Amplified Polymorphic DNA (RAPD). Ten RAPD types were found and 70% of the isolates were of RAPD types found in more than one cheese. The different RAPD types were identified to species level by Temporal Temperature Gradient Gel Electrophoresis (TTGE). Most of the isolates were identified as Lactobacillus paracasei (76%), but also Lactobacillus curvatus, Lactobacillus plantarum, Lactobacillus rhamnosus and some taxa originating from the starter culture were detected. In one cheese, no lactobacilli were found.One strain of the most frequent Lactobacillus RAPD type from each of the five cheeses with a Lactobacillus flora was used as adjunct cultures in a cheese model system. Four of the five adjuncts were re-isolated during ripening. Two adjunct containing model cheeses received higher flavour scores than the control while two other were associated with off-flavours. The two model cheeses with off-flavour had a similar microflora and both were after 13 weeks of ripening dominated by a strain identified as L. plantarum.
|
|
| 2. |
- Blixt, Y., et al.
(författare)
-
Interlaboratory random amplified polymorphic DNA typing of Yersinia enterocolitica and Y. enterocolitica-like bacteria
- 2003
-
Ingår i: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 83:1, s. 15-26
-
Tidskriftsartikel (refereegranskat)abstract
- A random amplified polymorphic DNA (RAPD) protocol was developed for interlaboratory use to discriminate food-borne Yersinia enterocolitica O:3 from other serogroups of Y. enterocolitica and from Y. enterocolitica-like species. Factors that were studied regarding the RAPD performance were choice of primers and concentration of PCR reagents (template DNA, MgCl 2, primer and Taq DNA polymerase). A factorial design experiment was performed to identify the optimal concentrations of the PCR reagents. The experiment showed that the concentration of the PCR reagents tested significantly affected the number of distinct RAPD products. The RAPD protocol developed was evaluated regarding its discrimination ability using 70 different Yersinia strains. Cluster analysis of the RAPD patterns obtained revealed three main groups representing (i) Y. pseudotuberculosis, (ii) Y. enterocolitica and (iii) Y. kristensenii, Y. frederiksenii, Y. intermedia and Y. ruckeri. Within the Y. enterocolitica group, the European serovar (O:3) and the North American serovar (O:8) could be clearly separated from each other. All Y. enterocolitica O:3 strains were found in one cluster which could be further divided into two subclusters, representing the geographical origin of the isolates. Thus, one of the subclusters contained Y. enterocolitica O:3 strains originating from Sweden, Finland and Norway, while Danish and English O:3 strains were found in another subcluster together with O:9 and O:5,27 strains. The repeatability (intralaboratory) and reproducibility (interlaboratory) of the RAPD protocol were tested using 15 Yersinia strains representing different RAPD patterns. The intralaboratory and the interlaboratory studies gave similarity coefficients of the same magnitude (generally >70%) for the individual strains. In the present study, it was shown that interreproducible RAPD results could be achieved by appropriate optimisation of the RAPD protocol. Furthermore, the study reflects the heterogeneous genetic diversity of the Y. enterocolitica species. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 3. |
- Dahlenborg, Maria, et al.
(författare)
-
Prevalence of Clostridium botulinum types B, E, and F in faecal samples from Swedish cattle.
- 2003
-
Ingår i: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 82:2, s. 105-110
-
Tidskriftsartikel (refereegranskat)abstract
- Faeces were collected from 60 cows at three slaughterhouses situated in southern and central Sweden. The faecal samples were collected during two sampling periods over the year, summer and winter. All samples were analysed for the presence of Clostridium botulinum spores, according to a combined selection and enrichment PCR procedure. One PCR assay was specific for part of the type B neurotoxin gene, while the other assay was specific for both type E and F neurotoxin genes. The prevalence of C. botulinum in Swedish cattle was established to be 73% for non-proteolytic type B and less than 5% for types E and F. Twenty-eight (64%) of the positive faecal samples had a spore load of less than 4 spores/g. Statistical analysis (ANOVA) showed that seasonal variation (summer and winter) had a significant effect on the prevalence of C. botulinum type B in cattle, whereas the effect of geographical location of rearing of the cattle (southern and central Sweden) was less significant.
|
|
| 4. |
- Johansson, M L, et al.
(författare)
-
Survival of Lactobacillus plantarum DSM 9843 (299v), and effect on the short-chain fatty acid content of faeces after ingestion of a rose-hip drink with fermented oats
- 1998
-
Ingår i: International Journal of Food Microbiology. - 0168-1605. ; 42:1-2, s. 29-38
-
Tidskriftsartikel (refereegranskat)abstract
- In a controlled and randomised double-blind study, 26 healthy adult volunteers consumed, for 21 d, 400 ml of a rose-hip drink containing oats (0.7 g/100ml) fermented with Lactobacillus plantarum DSM 9843 (RHL; containing 5 x 10(7) cfu ml(-1)), and 22 volunteers in a second group the same amount of a pure rose-hip drink (RH). Significant increases in the total faecal concentration of carboxylic acids (P < 0.05 after 1 week and P < 0.01 after 3 weeks of intake), acetic acid (P < 0.01 after 3 weeks of intake) and propionic acid (P < 0.01 after 3 weeks of intake and P < 0.05 eight days after intake ceased) were recorded in the RHL group, indicating increased fermentation in the colon. In both groups a significant increase was obtained in the concentration of faecal lactic acid (P < 0.001 after 1 and 3 weeks of intake). No changes were seen in the concentration of faecal butyrate. The numbers of faecal bifidobacteria and lactobacilli increased significantly in both groups after 3 weeks of intake. Sulphite-reducing clostridia rapidly decreased in the group receiving the product with Lb. plantarum DSM 9843 after 1 week of intake, and then also in the pure rose-hip group after 3 weeks of intake. No changes were seen in the numbers of total anaerobes, gram-negative anaerobes or total aerobes during administration. Lb. plantarum DSM 9843 was recovered in faeces from all volunteers in the RHL group. Median amounts were 7.0 (5.0-8.8) log10 cfu g(-1) after one week of intake, and 6.7 (5.0-8.9) log10 cfu g(-1) after 3 weeks, respectively. The strain was still recovered from faeces of five volunteers 8 d after administration ceased (> 4.8 log10 cfu g(-1)). During the period of intake the volunteers in the RHL group experienced a significant increase in stool volume, a significant decrease in flatulence and slightly softer stools. Volunteers in the RH group experienced a slight but significant decrease in stool volume.
|
|
| 5. |
- Knutsson, Rickard, et al.
(författare)
-
Development of a PCR-compatible enrichment medium for Yersinia enterocolitica: amplification precision and dynamic detection range during cultivation
- 2002
-
Ingår i: International Journal of Food Microbiology. - 0168-1605. ; 72:3, s. 185-201
-
Tidskriftsartikel (refereegranskat)abstract
- A Yersinia PCR-Compatible Enrichment (YPCE) medium was developed, which removes the necessity for sample pretreatment before PCR-based detection of Yersinia enterocolitica. The medium was designed through a sequence of independent screening and factorial design experiments to study the PCR inhibition and growth characteristics of medium components. The compatibility of the YPCE medium was evaluated using real-time PCR. The real-time PCR assay, based on the fluorescent double-stranded DNA binding dye SYBR green, generated approximately a 4-log linear range of amplification and in the range of 10(5)-10(8) (CFU/ml), the coefficient of variation <5%. When a background flora was present at concentrations greater than or equal to10(6) (CFU/ml), the DNA amplification was influenced and a change in the log-linear slope leading to a lower amplification efficiency was observed. To study the dynamic detection range and relative amplification precision during enrichment, Y. enterocolitica and background flora were inoculated at various concentrations. It was possible to detect inoculation concentrations of 10(1) (CFU/ml) Y enterocolitica in the presence of at least an inoculation concentration of 10(3) (CFU/ml) of an undefined background flora and the optimal conditions for sample withdrawal was in the range of 9 to 18 h enrichment. The YPCE medium can, especially for swab samples, form part of a simple analysis procedure allowing high throughput PCR. (C) 2002 Elsevier Science B.V. All rights reserved.
|
|
| 6. |
- Knutsson, Rickard, et al.
(författare)
-
Evaluation of selective enrichment PCR procedures for Yersinia enterocolitica.
- 2002
-
Ingår i: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 73:1, s. 35-46
-
Tidskriftsartikel (refereegranskat)abstract
- Four enrichment PCR protocols for detecting unlysed cells of pathogenic Yersinia enterocolitica were studied. First, the probability of detecting Y. enterocolitica cells of known concentrations by a multiplex PCR assay was determined, and it was found to follow a logistic regression model. From this model, the probability of detecting Y enterocolitica at a specific concentration could be estimated; for example, the detection probability of 10(4) CFU/ml was estimated to be 85.4%. The protocols were evaluated on enrichment cultures inoculated with 10(2) CFU/ml Y. enterocolitica and 10(2)-10(6) CFU/ml of a defined background flora. For each protocol, the time for sample withdrawal and the presence of background flora were studied with respect to PCR detection. The optimal point in time of sample withdrawal was found to be different for each protocol employed. Early detection was favoured by concentrating the target cells, and the most rapid PCR detection of Y. enterocolitica was achieved with enrichment in Yersinia-PCR-compatible-enrichment (YPCE) medium for 3 h at 25 degrees C, followed by a centrifugation prior to PCR analysis. For detection of Y. enterocolitica in the presence of high concentrations (10(6) CFU/ml) of background flora, a long incubation time followed by density centrifugation and a dilution step was most successful. The protocol that gave the most reliable PCR detection in the presence of 10(6) CFU/ml background flora included 24 h incubation in Yersinia-selective-enrichment (YSE) broth at 25 degrees C, followed by Percoll density centrifugation, and a 100 times dilution prior to PCR analysis.
|
|
| 7. |
- Malorny, B, et al.
(författare)
-
Standardization of diagnostic PCR for the detection of foodborne pathogens.
- 2003
-
Ingår i: International Journal of Food Microbiology. - 0168-1605. ; 83:1, s. 39-48
-
Tidskriftsartikel (refereegranskat)abstract
- In vitro amplification of nucleic acids using the polymerase chain reaction (PCR) has become, since its discovery in the 1980s, a powerful diagnostic tool for the analysis of microbial infections as well as for the analysis of microorganisms in food samples. However, despite its potential, PCR has neither gained wide acceptance in routine diagnostics nor been widely incorporated in standardized methods. Lack of validation and standard protocols, as well as variable quality of reagents and equipment, influence the efficient dissemination of PCR methodology from expert research laboratories to end-user laboratories. Moreover, the food industry understandably requires and expects officially approved standards. Recognizing this, in 1999, the European Commission approved the research project, FOOD-PCR (http://www.PCR.dk), which aims to validate and standardize the use of diagnostic PCR for the detection of pathogenic bacteria in foods. The present review focuses on the harmonization procedure and standardization criteria for detection of foodborne pathogens by PCR. The progress of standardization so far and future perspectives of diagnostic PCR are discussed.
|
|
| 8. |
- Olsson, Crister, et al.
(författare)
-
The bacterial flora of fresh and chill-stored pork: analysis by cloning and sequencing of 16S rRNA genes.
- 2003
-
Ingår i: International Journal of Food Microbiology. - 0168-1605. ; 83:3, s. 245-252
-
Tidskriftsartikel (refereegranskat)abstract
- The composition of the initial bacterial flora of pork and the development of the flora after storage at +4 °C for 4 days were analysed by amplification, cloning and sequencing of 16S rDNA. A total of 122 clones were obtained, with lengths of ≥400 nucleotides and ≥95% similarity to database sequences. Nineteen clones were similar to sequences in database not assigned to any genera. Fourteen different genera were represented in clones from fresh meat, with 36.5% of the clones most resembling Acinetobacter and 17.3% resembling Staphylococcus and Macrococcus. After storage, the clones were composed of six different genera, with 44.3% resembling Pseudomonas, 17.1% resembling Aeromonas and only 14.3% resembling Acinetobacter. This study shows that the overall pattern of the initial and chill-stored pork flora, as shown by a molecular approach, was in agreement with results obtained in previous studies using traditional cultivation methods.
|
|
| 9. |
- Andersson, Annika, et al.
(författare)
-
Comparison between automatic ribotyping and random amplified polymorphic DNA analysis of Bacillus cereus isolates from the dairy industry
- 1999
-
Ingår i: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 47:42006, s. 147-151
-
Tidskriftsartikel (refereegranskat)abstract
- Discrimination by automatic ribotyping and random amplified polymorphic DNA PCR, RAPD, was compared for 40 different B. cereus dairy isolates, 4 different B. mycoides isolates and 6 culture collection strains. RAPD-PCR has previously shown to be useful for tracing contamination routes of B. cereus to milk. Automatic ribotyping using EcoRI and PvuII separated the B. cereus and B. mycoides isolates/strains into 36 different ribotypes. RAPD-typing with primers generated 40 different RAPD-profiles. However, 17 isolates clustered into eight groups, irrespective of the primer and restriction enzyme used, and in all but one case, the isolates with the same pattern were isolated from the same dairy. Automatic ribotyping proved to be a useful, standardized and quick method to discriminate between B. cereus strains, only slightly less discriminatory than RAPD-typing.
|
|
| 10. |
- Andersson, Annika, et al.
(författare)
-
The adhesion of Bacillus cereus spores to epithelial cells might be an additional virulence mechanism
- 1998
-
Ingår i: International Journal of Food Microbiology. - 0168-1605 .- 1879-3460. ; 39:1-2, s. 93-9
-
Tidskriftsartikel (refereegranskat)abstract
- Four out of ten Bacillus cereus strains produced spores able to adhere to monolayers of Caco-2 cells (human epithelial cells). One of these strains has been involved in an outbreak of food poisoning where the symptoms were more severe and persisted for longer than a normal B. cereus food poisoning. The hydrophobicity of the spores is a contributing factor for the adhesion to occur. The spores are able to germinate in an environment similar to that of the small intestine and then the vegetative cells can produce the enterotoxin directly at the target place. A concentrated and active form of the enterotoxin will be taken up by the epithelial cells in the small intestine. Spore adhesion could be an important virulence factor for some B. cereus strains.
|
|
