| 1. |
- Alsanius, Beatrix, et al.
(författare)
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E. coli:s dolda liv: sockersug och kurragömma
- 2016
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Ingår i: LTV-fakultetens faktablad.
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Annan publikation (populärvet., debatt m.m.)abstract
- Frukt och grönsaker ingår i en hälsosam kost. Dessa konsumeras antingen i rå eller tillredd form. Ett ökat antal utbrott av tarmsmittor har dock relaterats till frukt och grönsaker för direktkonsumtion eller konsumtion med minimal tillredning, både i Sverige och utomlands. Ofta förknippas magsmittor på frukt och grönt med importerade varor. Det tragiska utbrottet av EHEC, en mycket aggressiv grupp av E. coli (serotyp O157:H7), sensommaren 2005 satte problematiken på den svenska kartan. För att skapa förutsättningar för att förebygga spridning av humanpatogena sjukdomsalstrare (såsom EHEC, Salmonella, Campylobacter) under odlingen till produkten har vi undersökt hur E. coli O157:H7 förökas på ytan av bladgrönsaker och i vilken omfattning den förmår att krypa in och gömma sig i bladvävnaden. Invasion i bladvävnaden innebär att den blir oåtkomlig vid tvättning. För bladgrönt fann vi att E. coli O157:H7- kan invadera både oskadd växtvävnad och växtvävnad som skadats antingen mekaniskt eller genom sjukdomsangrepp, - förmår att överleva och att växa till på ytan av intakta och tryckskadade, skurna och strimlade blad och - tillväxten är växtspecifik.Glukos och fruktos var de främsta sockerarterna på bladytan av intakta eller tryckskadade blad. Glukos, fruktos, sukros och galaktos förekom i stora mängder på skurna resp. sönderdelade blad. Ett mycket starkt samband mellan tillväxt av E. coli och sockerhalten konstaterades.Våra resultat visar att hög hygien måste råda i hela produktionskedjan från jord till bord. Att skölja grönsakerna innan förtäring har begränsad effekt och når inte de skadeorganismerna som har trängt in i växtvävnaden. Studien har genomförts inom ramen av Tvärlivs-projekt "Risker för humanpatogener i frukt och grönt i en globaliserad värld och strategier att bemästra dem", samt Partnerskap Alnarp projektet "Förekomst av tarmsmittor i bladgrönt under processing", båda i samarbete med Sydgrönt ek. för.
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| 2. |
- Alsanius, Beatrix, et al.
(författare)
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Internalization of Escherichia coli O157:H7 gfp+ in rocket and Swiss chard baby leaves as affected by abiotic and biotic damage
- 2017
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Ingår i: Letters in Applied Microbiology. - : Oxford University Press (OUP). - 0266-8254 .- 1472-765X. ; 65, s. 35-41
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Tidskriftsartikel (refereegranskat)abstract
- Internalization of human pathogens in edible parts of vegetables eaten raw is a major concern, since once internalized they are protected from sanitizing treatments. In this study, we examined the invasion of gfp-labelled Escherichia coli O157:H7 into intact and biotically (infection with Xanthomonas campestris/Pseudomonas syringae) and abiotically (grating with silicon carbide) damaged leaves of wild rocket (Diplotaxis tenuifolia) and Swiss chard (Beta vulgaris subsp. cicla) using laser scanning confocal microscopy. Bacterial cells were found in internal locations of the tissue, irrespective of tissue health status. Contaminated leaf sections of biotically and abiotically damaged wild rocket leaves showed higher susceptibility to microbial invasion, while the pathogen was internalized in greater numbers into intact Swiss chard leaf sections when abiotically, but not biotically, damaged. The greatest differences were observed between the plant species; after surface sanitization, E.coli O157:H7 was still detected in wild rocket leaves, but not in Swiss chard leaves.Significance and Impact of the StudyContamination of leafy vegetables with Escherichia coli O157:H7 is a growing problem, as reported outbreaks are increasing. However, establishment of this human pathogen in the phyllosphere is not completely understood. Using laser scanning confocal microscopy, we demonstrated that E.coli O157:H7gfp+ can invade plant tissue of Swiss chard and wild rocket leaves and that the bacterium is more sensitive to surface sanitization of Swiss chard leaves. Damage to leaf tissue promoted leaf invasion, but the nature of the damage (abiotic or biotic) and plant species had an impact.
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| 3. |
- Alsanius, Beatrix, et al.
(författare)
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Ornamental flowers in new light: Artificial lighting shapes the microbial phyllosphere community structure of greenhouse grown sunflowers (Helianthus annuus L.)
- 2017
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Ingår i: Scientia Horticulturae. - : Elsevier BV. - 0304-4238 .- 1879-1018. ; 216, s. 234-247
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Tidskriftsartikel (refereegranskat)abstract
- Artificial assimilation lighting is a common practice in greenhouse horticulture in the circumpolar region to compensate for natural low light conditions. To modulate plant architecture, regulate flowering of photoperiodic crops, increase plant performance per energy input and consequently profitability, light emitting diodes (LEDs) have been suggested as a powerful tool for ornamental growers in complementary or replacement of conventional lighting such as incandescent, fluorescent and high pressure sodium (HPS) lamps. As LED light differs from HPS lamps with regard to spectral output, light distribution as well as heat emission, the microclimate within the crop stand is affected. In two independent experiments conducted in fall and winter, we therefore compared the effect of two types of LED light (red 660 nm + blue 460 nm LED, 80:20 RB-LED; white LED, W-LED) with HPS lighting on ornamental sunflowers (Helianthus annuus cv. 'Teddy Bear'). Depending of the solar radiation (fall vs winter experiments), a same PPFD of 70-120 mu mol m(-2) s(-1) of artificial lighting (photoperiod of 16 h) was given at the top of the plants. Plant growth performance and biomass, leaf temperature, photobiological parameters (photosynthetic activity, stomatal conductance, chlorophyll fluorescence) as well as the leaf associated microbiome, assessed using culture dependent and independent methods on apical, directly exposed to the light treatments, and basal leaves, were studied. As expected, significant differences were obtained for plant related parameters between the two repetitions of the experiment due to difference in solar radiation. Light treatments influenced plant growth performance which was lower for all parameters in sunflowers exposed to LEDs than HPS. However, no differences were found with respect to photobiological parameters. Top leaf temperature was higher in the presence of HPS than LEDs, which explained the lower plant growth performance observed under LED regimes. Colony-forming units representing culturable fungi and fluorescent pseudomonads were higher on basal leaves than on apical ones, but did not vary with respect to light treatments. On the other hand, biodiversity estimated with respect to species abundance and evenness (Shannon-H index) and species richness (Chao1) revealed different patterns for the fungal and bacterial microbiome. Regardless of the leaf position, light treatments affected fungal species abundance and evenness, which was highest on leaves exposed to HPS, but not species richness. The fungal microbiome was more diverse on apical than on basal leaves. For the bacterial microbiome, biodiversity estimates differed between the repetitions. Interactions between leaf temperature and bacterial genera were found for several of the dominant genera in the sunflower phyllosphere (Pseudomonas, Staphylococcus, Enhydro bacter) while other decisive bacterial and fungal genera were correlated to photobiological parameters, e.g. Bradyrhizobium, Sphingomonas, Brevibatericum, Bacillus, Hypotrachyna, Aureobasidium. The use of "new light" in greenhouse ornamentals is not only a technological change modifying plant morphology and development, but also affects the microbial ecology on plant surfaces, implying consequences on plant protection issues and biological control strategies. (C) 2017 Elsevier B.V. All rights reserved.
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| 6. |
- Darlison, Julia, et al.
(författare)
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Plant species affects establishment of Escherichia coli O157:H7 gfp+ on leafy vegetables
- 2019
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Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 127, s. 292-305
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Tidskriftsartikel (refereegranskat)abstract
- Aims Greenhouse trials were conducted with different cultivars of baby leaf spinach, rocket and Swiss chard and inoculation of Escherichia coli O157:H7 gfp+, to determine whether plant species and cultivar have an impact on the establishment of this strain. Methods and Results Three cultivars each of spinach, rocket and Swiss chard were spray inoculated with E. coli O157:H7 gfp+ at doses of log 7 CFU per ml. Due to the different lengths of growing period spinach and Swiss chard were spray inoculated three times and rocket five times, with final inoculation performed 3 days prior to harvest. After a growing period of 26-33 days, E. coli O157:H7 gfp+ was recovered from the leaf surface in mean populations between log 1 and 6 CFU per gram. The lowest occurrence of E. coli O157:H7 gfp+ was found on rocket leaves and the highest on spinach. There was no significant difference in the establishment of E. coli O157:H7 gfp+ between cultivars, but there were differences between plant species. Indigenous phyllosphere bacteria were pure cultured and identified with 16S rRNA gene sequencing. Conclusions Despite the same high inoculation dose of E. coli O157:H7 gfp+ on leaves, the establishment rate differed between plant species. However, plant cultivar did not affect establishment. Pantoea agglomerans dominated the identified bacterial isolates. Significance and Impact of the Study As previous studies are inconclusive on choice of model plant species and cultivar, we studied whether plant species or cultivar determines the fate of E. coli O157:H7 gfp+ on leafy vegetables. The findings indicate that plant species is a key determinant in the establishment of E. coli O157:H7 gfp+.
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| 7. |
- Hartmann, Rahel, et al.
(författare)
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Impact of the source of organic manure on persistence of E. coli O157:H7 gfp+ in rocket (Diplotaxis tenuifolia) and Swiss chard (Beta vulgaris cicla)
- 2017
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Ingår i: Food Control. - : Elsevier BV. - 0956-7135 .- 1873-7129. ; 81, s. 200-210
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Tidskriftsartikel (refereegranskat)abstract
- The influence of organic nitrogen sources on the establishment of E. coil 0157:H7 and the occurrence of other potentially human pathogenic bacteria on baby leaf salads was evaluated. Greenhouse-grown rocket and Swiss chard were spray-inoculated with gfp-tagged E. coil 0157:H7 twice a week from when their first true leaves reached a length of 2 cm until three days before harvest. Analysis of nitrogen content in leaves revealed differences between treatments. Untreated plants had the lowest values, followed by plants fertilized with pig hair pellets and chicken manure. The same pattern was seen for the growth medium at the day of harvest. The applied strain showed similar establishment (measured using culture-dependent methods) irrespective of treatment, but Swiss chard hosted significantly more E. coli 0157:H7 than rocket. Differences in the risk of infection were found for the crops, with plants fertilized with pig hair pellets showing a slightly higher risk. No relationship was found for total nitrogen content in leaves and colonization with E. coli 0157:H7 gfp+. Isolating dominant Enterobacteriaceae from leaves, some strains showed conformity to bacterial species that have previously been identified to influence the establishment of E. coli 0157:H7 in the phyllosphere. In this study, no inhibitory effects were observed in vitro.Colonies showing matching characteristics for Listeria spp. and Salmonella spp. were detected up to 5.5 and 5 log CFU g(-1) fresh weight, respectively. However, presumptive Listeria spp. and Salmonella spp. could not be confirmed by sequencing of the 16S rRNA gene. (C) 2017 Elsevier Ltd. All rights reserved.
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