| 1. |
- 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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| 2. |
- Bakeeva, Albina, et al.
(författare)
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Distribution of mycotoxins produced by Penicillium spp. inoculated in apple jam and creme fraiche during chilled storage
- 2019
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 292, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- Estimations of consumer exposure to mycotoxins through surveillance of mycotoxins in the food trade are well described, but the exposure due to mouldy food in private homes is not known, and may result from removing visible mould on food and eating the rest. In this study, we followed the growth of Penicillium expansum on the surface of apple jam and Penicillium verrucosum on creme fraiche, as well as production and distribution of fungal metabolites throughout the sample (approx. 6 cm high divided into three equal layers), using a multianalyte method, over time (up to 28 days) and at 4, 8 and 15 degrees C.Growth rates and apparent lag times for P. expansum in apple jam at different temperatures were estimated by fitting to the Baranyi model. The growth rates were 1.7, 2.7 and 4.3 mm day(-1) for storage at 4, 8 and 15 degrees C, respectively; apparent lag times decreased with increasing storage temperature and were 10.6, 7.9 and 2.6 days at corresponding temperatures. Patulin and roquefortine C were identified and quantified, among other fungal metabolites. Patulin was detected in all 2-cm layers of the apple jam at 15 degrees C. Concentrations in the upper two layers of the jar corresponded to exposures exceeding the health based guidance value (HBGV) for a normal serving size. Consequently, removal of the mouldy part is insufficient to avoid unhealthy exposure. In contrast to patulin, roquefortine C was also produced at 4 degrees C.The growth of P. verrucosum on creme fraiche was very restricted and could not be modelled. Despite the small colony (8 +/- 0.5 mm in diameter), ochratoxin A and citrinin were detected after 21 days at 15 degrees C in the top 2 cm layer (including the fungal colony), and at concentrations in a normal serving corresponding to an exposure above the HBGV established by EFSA for both mycotoxins. Questiomycin A, an antibiotic, was also produced in creme fraiche but in contrast to the two mycotoxins, was detected throughout all layers of the creme fraiche and was produced also at 4 and 8 degrees C.As a complement to a previous study, we also present production and the distribution of major fungal metabolites in apple jam and creme fraiche for some additional fungal strains (P. crustosum, P. roqueforti and P. verrucosum on apple jam and P. expansum on creme fraiche). A pilot study investigating the effect of inoculation size on toxin production may have implications for the best inoculum to use in experimental studies.
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| 3. |
- Boqvist, Sofia, et al.
(författare)
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Escherichia coli O157:H7 reduction in hamburgers with regard to premature browning of minced beef, colour score and method for determining doneness
- 2015
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 215, s. 109-116
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated the effect of premature browning (PMB) on the survival of Escherichia coli O157:H7 in beef hamburgers after cooking with respect to interior colour of the hamburger and recommendations to cook hamburgers to a core temperature of 71 degrees C. Assessment of doneness by visual inspection or measurement of internal temperature was compared in terms of survival and the increased relative risk of illness due to PMB was estimated. At the last consume-by-day, hamburgers made from minced meat packaged in 80/20 O-2/CO2 (MAP hamburger) and from meat minced at retail packaged in atmospheric condition (control hamburger) were inoculated with a gfp-tagged strain of E. coli O157:H7 (E. coli O157:H7gfp+). Hamburgers were cooked for different times during assessment of the core temperature every 30 s and cut in halves after cooking. Doneness was evaluated based on visual judgement of the internal colour using a score chart (C-score) from 'uncooked' (score 1) to 'tan with no evidence of pink' (score 5). An alternative five point score chart (TCC-score) including texture of the meat, clarity of meat juice and internal colour was also developed. Enumeration of viable E. coli O157:H7gfp+ in cooked hamburgers was based on fluorescent colonies recovered from plates. Results showed that MAP hamburgers developed PMB when compared with controls (P = 0.0003) and that the shortest cooking time for the highest C-score was 6 and 11 min for MAP and control hamburgers, respectively. The mean temperature in the MAP hamburger was then 60.3 degrees C. The TCC-score reduced the difference between MAP and control hamburgers. It was also shown that the survival of E. coli O157:H7gfp+ was highest in MAP hamburgers. The predicted absolute risks for illness were highest for MAP hamburgers for all C-scores and the relative risk associated with PMB increased with doneness. For a C-score of 4 (slightly pink) the predicted relative risk for illness was 300 times higher for MAP hamburger than for controls. A variable pathogen reduction was observed when cooking hamburgers to temperatures of 70-76 degrees C (the 5th and 95th percentile range was around 33 log CFU). The lower reductions, at the 5th percentile, may, depending on initial contamination levels, not be enough to ensure sufficient and safe inactivation of E. coli O157:H7. Efforts to inform consumers about PMB in minced meat packaged in high oxygen packages (>= 60% O-2) are needed with the aim to make consumers use thermometers correctly or at least not determine doneness based only on meat colour. (C) 2015 Elsevier B.V. All rights reserved.
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| 4. |
- Jacobson, Magdalena, et al.
(författare)
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Flotation—A New Method to Circumvent PCR Inhibitors in the Diagnosis of Lawsonia intracellularis
- 2009
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Ingår i: International Journal of Food Microbiology. - : Hindawi Limited. - 0168-1605 .- 1879-3460 .- 1687-918X .- 1687-9198. ; 2009
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Tidskriftsartikel (refereegranskat)abstract
- The obligate intracellular bacteriumLawsonia intracellulariscauses enteritis and poor growth in weaned pigs. Cultivation is difficult and diagnosisante mortemis mainly based on techniques such as polymerase chain reaction. However, false negative results caused by the presence of PCR-inhibitory factors constitute a problem. This study aimed to develop and evaluate a new technique, flotation, to separateL. intracellularisfrom inhibitors in faeces prior to PCR. The technique was evaluated by comparison to two previously evaluated and commonly used methods, preparation by boiling lysate combined with nested PCR and preparation by a commercial kit combined with conventional PCR. Continuous density centrifugation of faecal samples containingL. intracellularissuggested the buoyant density of the microbe to be between 1.064 and 1.077 g/mL. Several flotation setups were tested to achieve optimal separation of the microbe from inhibitors and faecal particles. The finally selected setup floated wholeL. intracellularisfrom the application site at the bottom to the upper part of the gradient while inhibitory components mainly remained in the bottom. PCR was performed directly on material recovered from the upper interphase. The method was evaluated on 116 clinical samples. As compared to sample preparation by boiling combined with nested PCR, fewer samples were inhibited but also fewer positives were identified. In comparison to preparation by a commercial kit combined with conventional PCR, presently used for routine diagnosis, similar results were obtained. However, the new method was comparably faster to perform. The new method, based on flotation ofLawsonia intracellulariscombined with conventional PCR, was well suited for routine diagnosis.
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| 5. |
- Jensen, Dan Funck
(författare)
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Characterization of microbial communities and fungal metabolites on field grown strawberries from organic and conventional production
- 2013
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 160, s. 313-322
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Tidskriftsartikel (refereegranskat)abstract
- The background levels of culturable indigenous microbial communities (microbiotas) on strawberries were examined in a field survey with four conventional and four organic growers with different production practise and geographic distribution. The microbiota on apparently healthy strawberries was complex including potential plant pathogens, opportunistic human pathogens, plant disease biocontrol agents and mycotoxin producers. The latter group was dominated by Penicillium spp. and Aspergillus niger was also isolated. As expected, bacteria were the most abundant and diverse group of the strawberry microbiota followed by yeasts and filamentous fungi. No obvious correlation between grower practice and the strawberry microbiota was observed. Differences between microbiotas on strawberries from conventional systems with up to 10 fungicide spray treatments and organic production systems were insignificant. Mycotoxins were not detected in mature strawberries from any of the eight different growers neither in additional samples of low quality berries. However, isolates of Penicillium expansum and A. niger produced high amounts of mycotoxins when incubated on strawberries at 25 degrees C. Penicillium polonicum produced cyclopenol, cyclopenin, and viridicatin on the artificially infected berries, while Altemaria arborescens produced tenuazonic acid, Alternaria tenuissima produced altertoxin land altenuene, and Trichoderma spp. produced several peptaibols. In conclusion, native strawberry microbiotas are highly diverse both in terms of taxonomic groups and functional traits that are important in relation to plant and human health. (C) 2012 Elsevier B.V. All rights reserved.
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| 6. |
- Karlsson, Ida, et al.
(författare)
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Agricultural factors affecting Fusarium communities in wheat kernels
- 2017
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 252, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- Fusarium head blight (FHB) is a devastating disease of cereals caused by Fusarium fungi. The disease is of great economic importance especially owing to reduced grain quality due to contamination by a range of mycotoxins produced by Fusarium. Disease control and prediction is difficult because of the many Fusarium species associated with FHB. Different species may respond differently to control methods and can have both competitive and synergistic interactions. Therefore, it is important to understand how agricultural practices affect Fusarium at the community level.Lower levels of Fusariwn mycotoxin contamination of organically produced cereals compared with conventionally produced have been reported, but the causes of these differences are not well understood. The aim of our study was to investigate the effect of agricultural factors on Fusarium abundance and community composition in different cropping systems. Winter wheat kernels were collected from 18 organically and conventionally cultivated fields in Sweden, paired based on their geographical distance and the wheat cultivar grown. We characterised the Fusarium community in harvested wheat kernels using 454 sequencing of translation elongation factor 1-alpha amplicons. In addition, we quantified Fusariwn spp. using real-time PCR to reveal differences in biomass between fields.We identified 12 Fusariwn operational taxonomic units (OTUs) with a median of 4.5 OTUs per field. Fusarium graminearum was the most abundant species, while F. avenaceum had the highest occurrence. The abundance of Fusariwn spp. ranged two orders of magnitude between fields. Two pairs of Fusariurt species co-occurred between fields: F. poae with F. tricinctwn and F. culmorwn with F. sporofrichoides. We could not detect any difference in Fusariwn communities between the organic and conventional systems. However, agricultural intensity, measured as the number of pesticide applications and the amount of nitrogen fertiliser applied, had an impact on Fusariwn communities, specifically increasing the abundance of F. tricinctwn. There were geographical differences in the Fusarium community composition where F. graminearwn was more abundant in the western part of Sweden. The application of amplicon sequencing provided a comprehensive view of the Fusarium community in cereals. This gives us better opportunities to understand the ecology of Fusarium spp., which is important in order to limit FHB and mycotoxin contamination in cereals.
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| 7. |
- Kolseth, Anna-Karin
(författare)
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Draft genome sequence and chemical profiling of Fusarium langsethiae, an emerging producer of type A trichothecenes
- 2016
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 221, s. 29-36
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Tidskriftsartikel (refereegranskat)abstract
- Fusarium langsethiae is a widespread pathogen of small grain cereals, causing problems with T-2 and HT-2 toxin contamination in grains every year. In an effort to better understand the biology of this fungus, we present a draft genome sequence of F. langsethiae Fl201059 isolated from oats in Norway. The assembly was fragmented, but reveals a genome of approximately 37.5 Mb, with a GC content around 48%, and 12,232 predicted protein-coding genes. Focusing on secondary metabolism we identified candidate genes for 12 polyketide synthases, 13 non ribosomal peptide synthetases, and 22 genes for terpene/isoprenoid biosynthesis. Some of these were found to be unique compared to sequence databases. The identified putative Tri5 cluster was highly syntenic to the cluster reported in F. sporotrichioides. Fusarium langsethiae Fl201059 produces a high number of secondary metabolites on Yeast Extract Sucrose (YES) agar medium, dominated by type A trichothecenes. Interestingly we found production of glucosylated HT-2 toxin (Glu-HT-2), previously suggested to be formed by the host plant and not by the fungus itself. In greenhouse inoculations of F. langsethiae FI201059 on barley and oats, we detected the type A trichothecenes: neosolaniol, HT-2 toxin, T-2 toxin, Glu-HT-2 and numerous derivatives of these. (C) 2016 Elsevier B.V. All rights reserved.
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| 8. |
- Leong, Su-lin L., et al.
(författare)
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The extreme xerophilic mould Xeromyces bisporus : Growth and competition at various water activities
- 2011
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Ingår i: International Journal of Food Microbiology. - Amsterdam, Netherlands : Elsevier. - 0168-1605 .- 1879-3460. ; 145:1, s. 57-63
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the mould, Xeromyces bisporus, unique in its strong xerophilicity and ability to grow at water activity (a(w)) 0.62, lower than for any other known organism. The linear growth rates of one fast and one slow-growing strain of X. bisporus were assessed at 20, 25, 30 and 37 degrees C on solid agar media containing a mixture of glucose and fructose to reduce a(w) to 0.94, 0.88, 0.84, 0.80, 0.76 and 0.66. Growth rates of xerophilic species closely related to X. bisporus, viz. Chrysosporium Mops, C. xerophilum and Monascus eremophilus, were also assessed. Optimal conditions for growth of both X. bisporus strains were approx. 0.84 a(w) and 30 degrees C, despite FRR 2347 growing two- to five-fold faster than CBS 185.75. X. bisporus FRR 2347 even grew well at 0.66 a(w) (0.48 mm/day). C. Mops and C xerophilurn were more tolerant of high a(w) than X. bisporus. and could be differentiated from each other based on: the faster growth of C. xerophilum; its preference for temperatures >= 30 degrees C and a(w) >= 0.94 (c.f. <= 25 degrees C and similar to 0.88 a(w) for C Mops); and its ability to grow at 0.66 a(w), which is the lowest a(w) reported to date for this species. M. eremophilus grew slowly (max. 0.4 mm/day) even in its optimal conditions of similar to 0.88 a(w) and 25 degrees C. To investigate the competitive characteristics of X. bisporus at low a(w), both X. bisporus strains were grown in dual-culture with xerotolerant species Aspergillus flavus and Penicillium roqueforti, and xerophilic species A. penicillioides, C. Mops, C. xerophilum and Eurotium chevalieri, on glucose-fructose agar plates at 0.94, 0.84, 0.80 and 0.76 a(w) and at 25 degrees C. Growth rates and types of interactions were assessed. Excretion of inhibitory substances acting over a long-range was not observed by any species; inhibitors acting over a short-range that temporarily slowed competitors' growth or produced a protective zone around the colony were occasionally observed for A. penicillioides, C. Mops and C. xerophilum. Instead, rapid growth relative to the competitor was the most common means of dominance. The xerotolerant species. A. flavus and P. roqueforti were dominant over X. bisporus at 0.94 a(w). E. chevalieri was often dominant due to its rapid growth over the entire a(w) range. At a(w) < 0.80, X. bisporus was competitive because it grew faster than the other species examined. This supports the concept that its ideal environmental niche is sugary foods with low a(w).
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| 9. |
- Lind, Helena, et al.
(författare)
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Glycerol Enhances the Antifungal Activity of Dairy Propionibacteria
- 2010
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Ingår i: International Journal of Food Microbiology. - New York, USA : Hindawi Limited. - 0168-1605 .- 1879-3460 .- 1687-918X .- 1687-9198. ; 2010
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Tidskriftsartikel (refereegranskat)abstract
- Dairy propionibacteria are widely used in starter cultures for Swiss type cheese. These bacteria can ferment glucose, lactic acid, and glycerol into propionic acid, acetic acid, and carbon dioxide. This research examined the antifungal effect of dairy propionibacteria when glycerol was used as carbon source for bacterial growth. Five type strains of propionibacteria were tested against the yeast Rhodotorula mucilaginosa and the molds Penicillium commune and Penicillium roqueforti. The conversion of 13C glycerol by Propionibacterium jensenii was followed with nuclear magnetic resonance. In a dual culture assay, the degree of inhibition of the molds was strongly enhanced by an increase in glycerol concentrations, while the yeast was less affected. In broth cultures, decreased pH in glycerol medium was probably responsible for the complete inhibition of the indicator fungi. NMR spectra of the glycerol conversion confirmed that propionic acid was the dominant metabolite. Based on the results obtained, the increased antifungal effect seen by glycerol addition to cultures of propionibacteria is due to the production of propionic acid and pH reduction of the medium
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| 10. |
- Lindqvist, Roland
(författare)
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Time to growth and inactivation of three STEC outbreak strains under conditions relevant for fermented sausages
- 2011
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 145, s. 49-56
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Tidskriftsartikel (refereegranskat)abstract
- Published models predicting growth and survival capabilities of shiga-toxin-producing Escherichia coil (STEC) under a(w) and lactic acid stress were validated by performing experiments with fermented sausage associated outbreak strains. Strain variation in inactivation and time to growth (TIC) were investigated for strains representing three serotypes (0103, 0111, and 0157). The TIC and growth boundaries of each strain were compared with predictions of a model for generic acid adapted E. coli and survival with predictions of two inactivation models. In addition, the influence of strain variation on the performance of the inactivation models, in terms of bias and accuracy factors, was illustrated. Strains with induced acid tolerance were used in broths containing 50 or 110 mM total lactic acid. The concentration of undissociated lactic acid (HLac) was adjusted by setting the pH-value, and water activity (0.900 to 0.995 depending on experiment) was adjusted by adding NaCl. The survival capabilities of the outbreak strains were good compared to the model predictions. The average bias factors of inactivation model predictions were within a factor of 2.2 depending on the strain used to validate the model indicating that inactivation rates of outbreak strains were slower than predicted. However, the observed rates were similar to the rates of a previously studied acid tolerant generic E. coil strain. Similarly, the time to growth of two of the strains (0103 and 0157) was comparable with model predictions, whereas the growth capability of the third strain (0111) was lower than predicted. These results suggest that the properties of the most tolerant sausage outbreak strains are comparable to tolerant generic E. coli strains, which imply that suitable non-pathogenic E. coli strains are valid surrogates for fermented sausage outbreak strains. The relative sensitivity of strains depended on the environmental parameters and the response evaluated. The strain with the smallest log reduction at 20 C was 0157, whereas it was strain 0103 at 8 degrees C. Under conditions unfavorable for growth, the time to growth was much shorter for strains 0103 and O157 than for strain O111, whereas differences between strains were negligible under conditions favorable for growth. Depending on the response variable and the specific application the limitation of not addressing strain variation may lead to biased, fail-dangerous, predictions. Thus, solutions on how to best address strain variation in the development and validation of predictive models are needed. (c) 2010 Elsevier B.V. All rights reserved.
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