| 1. |
- Artin, Ingrid, et al.
(författare)
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Effects of carbon dioxide on neurotoxin gene expression in nonproteolytic Clostridium botulinum type E
- 2008
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 74:8, s. 2391-2397
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Tidskriftsartikel (refereegranskat)abstract
- Carbon dioxide is an antimicrobial gas commonly used in modified atmosphere packaging. In the present study, the effects of carbon dioxide on the growth of and neurotoxin production by nonproteolytic Clostridium botulinum type E were studied during the growth cycle. Quantitative reverse transcription-PCR and an enzyme-linked immunosorbent assay were used to quantify expression of the type E botulinum neurotoxin gene (cntE) and the formation of type E neurotoxin. The expression levels of cntE were similar in two strains, with relative expression peaking in the transition between exponential phase and stationary phase. In stationary phase, cntE mRNA expression declined rapidly. The cntE mRNA half-life was calculated to be approximately 9 minutes. Neurotoxin formation occurred in late exponential phase and stationary phase. High carbon dioxide concentrations delayed growth by increasing the lag time and decreasing the maximum growth rate. The effects of carbon dioxide concentration on relative neurotoxin gene expression and neurotoxin formation were significant. Expression of cntE mRNA and the formation of extracellular neurotoxin were twofold higher with a headspace carbon dioxide concentration of 70% (vol/vol) compared to 10% (vol/vol). This finding sheds a new, cautionary light on the potential risks of botulism associated with the use of modified atmosphere packaging. Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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| 2. |
- Eliasson, Lovisa, et al.
(författare)
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A comparative study of infrared and microwave heating for microbial decontamination of paprika powder
- 2015
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- There is currently a need in developing new decontamination technologies for spices due to limitations of existing technologies, mainly regarding their effects on spices’ sensory quality. In the search of new decontamination solutions, it is of interest to compare different technologies, to provide the industry with knowledge for taking decisions concerning appropriate decontamination technologies for spices. The present study compares infrared (IR) and microwave decontamination of naturally contaminated paprika powder after adjustment of water activity to 0.88. IR respectively microwave heating was applied to quickly heat up paprika powder to 98°C, after which the paprika sample was transferred to a conventional oven set at 98°C to keep the temperature constant during a holding time up to 20 min. In the present experimental set-up microwave treatment at 98°C for 20 min resulted in a reduction of 4.8 log units of the total number of mesophilic bacteria, while the IR treatment showed a 1 log unit lower reduction for the corresponding temperature and treatment time. Microwave and IR heating created different temperature profiles and moisture distribution within the paprika sample during the heating up part of the process, which is likely to have influenced the decontamination efficiency. The results of this study are used to discuss the difficulties in comparing two thermal technologies on equal conditions due to differences in their heating mechanisms
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| 3. |
- Eliasson, Lovisa, et al.
(författare)
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Infrared Decontamination of Oregano: Effects on Bacillus cereus Spores, Water Activity, Color, and Volatile Compounds
- 2014
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Ingår i: Journal of Food Science. - : Wiley. - 0022-1147 .- 1750-3841. ; 79:12, s. E2447-E2455
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Tidskriftsartikel (refereegranskat)abstract
- Infrared (IR) heating, a novel technology for decontaminating oregano, was evaluated by investigating the reduction of inoculated Bacillus cereus spores and the effect on water activity (aw), color, and headspace volatile compounds after exposure to IR treatment. Conditioned oregano (aw 0.88) was IR-treated in a closed heating unit at 90 and 100 °C for holding times of 2 and 10 min, respectively. The most successful reduction in B. cereus spore numbers (5.6 log units) was achieved after a holding time of 10 min at 90 °C, while treatment at 100 °C for the same time resulted in a lower reduction efficiency (4.7 log units). The lower reduction at 100 °C was probably due to a reduced aw (aw 0.76) during IR treatment or possibly to the alteration or loss of volatile compounds possessing antimicrobial properties. The green color of oregano was only slightly affected, while the composition of volatile compounds was clearly altered by IR heating. However, two of the key aroma compounds, carvacrol and thymol, were only slightly affected, compared to the effect on the other studied compounds, indicating that the typical oregano aroma can likely be preserved. In conclusion, IR heating shows potential for the successful decontamination of oregano without severe alteration of its color or the key aroma compounds, carvacrol and thymol. Practical Application: This study investigated the potential of infrared heating as a technology for decontaminating oregano. The study outcome contributes to the development of new decontamination solutions to improve the sensory and microbial quality of herbs and spices.
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| 4. |
- Gerits, Evelien, et al.
(författare)
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Antibacterial activity of a new broad-spectrum antibiotic covalently bound to titanium surfaces
- 2016
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Ingår i: Journal of Orthopaedic Research. - : John Wiley and Sons Inc.. - 0736-0266 .- 1554-527X. ; 34:12, s. 2191-2198
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Tidskriftsartikel (refereegranskat)abstract
- Biofilm-associated infections, particularly those caused by Staphylococcus aureus, are a major cause of implant failure. Covalent coupling of broad-spectrum antimicrobials to implants is a promising approach to reduce the risk of infections. In this study, we developed titanium substrates on which the recently discovered antibacterial agent SPI031, a N-alkylated 3, 6-dihalogenocarbazol 1-(sec-butylamino)-3-(3,6-dichloro-9H-carbazol-9-yl)propan-2-ol, was covalently linked (SPI031-Ti). We found that SPI031-Ti substrates prevent biofilm formation of S. aureus and Pseudomonas aeruginosa in vitro, as quantified by plate counting and fluorescence microscopy. To test the effectiveness of SPI031-Ti substrates in vivo, we used an adapted in vivo biomaterial-associated infection model in mice in which SPI031-Ti substrates were implanted subcutaneously and subsequently inoculated with S. aureus. Using this model, we found a significant reduction in biofilm formation (up to 98%) on SPI031-Ti substrates compared to control substrates. Finally, we demonstrated that the functionalization of the titanium surfaces with SPI031 did not influence the adhesion and proliferation of human cells important for osseointegration and bone repair. In conclusion, these data demonstrate the clinical potential of SPI031 to be used as an antibacterial coating for implants, thereby reducing the incidence of implant-associated infections.
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| 5. |
- Liebens, Veerle R., et al.
(författare)
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Identification and characterization of an anti-pseudomonal dichlorocarbazol derivative displaying anti-biofilm activity
- 2014
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Ingår i: Bioorganic & Medicinal Chemistry Letters. - : Elsevier BV. - 0960-894X .- 1464-3405. ; 24:23, s. 5404-5408
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Tidskriftsartikel (refereegranskat)abstract
- Pseudomonas aeruginosa strains resistant towards all currently available antibiotics are increasingly encountered, raising the need for new anti-pseudomonal drugs. We therefore conducted a medium-throughput screen of a small-molecule collection resulting in the identification of the N-alkylated 3,6-dihalogenocarbazol 1-(sec-butylamino)-3-(3,6-dichloro-9H-carbazol-9-yl)propan-2-ol (MIC = 18.5 ?g mL-1). This compound, compound 1, is bacteriostatic towards a broad spectrum of Gram-positive and Gram-negative pathogens, including P. aeruginosa. Importantly, 1 also eradicates mature biofilms of P. aeruginosa. 1 displays no cytotoxicity against various human cell types, pointing to its potential for further development as a novel antibacterial drug.
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| 6. |
- Lövenklev, Maria
(författare)
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A Molecular Approach for Investigation of the Prevalence and Neurotoxin Formation of Clostridium botulinum in Food Safety Assessment.
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the development of new food products, more knowledge is needed about the occurrence and quantity of food-borne pathogens in the food chain to be able to implement effective control measures and assure food safety. In addition, improved understanding of how environmental factors and food preservatives effect the microbial virulence expression in foods will enable the formulation of new strategies for food preservation and risk assessment. In this thesis, novel tools based on PCR methodology have been developed for the investigation of the prevalence of Clostridium botulinum in primary production and for monitoring the botulinum neurotoxin (BoNT) gene expression in the presence of common food preservatives. A semiquantitative enrichment PCR method was designed for the detection of low numbers of spores of C. botulinum types B, E and F in faecal samples from pigs and cattle. The method was able to detect 10 spores of C. botulinum type B per gram faeces with > 95% detection probability. The enrichment PCR was used in two surveys to determine the incidence and quantity of C. botulinum spores in pigs and cattle at slaughterhouses in Sweden. The results revealed that the prevalence was high; 62% in pigs and 73% in cattle regarding C. botulinum type B, with a higher incidence during winter than summer. Less than 4 spores per gram faeces were found in 71% of the positive samples in pigs and in 64% of the positive samples from cattle. Quantitative reverse transcription-PCR (qRT-PCR) methods were developed to monitor the relative BoNT gene expression in C. botulinum types B and E. The bont expression followed the growth cycle in both C. botulinum type B and type E with a maximum in expression as the bacteria entered the stationary growth phase. The relative levels of bontB expression in different strains of C. botulinum type B was found to be well correlated to the neurotoxin formation and the toxicity. The bontB specific qRT-PCR method was used to study the effect of CO2, NaCl and NaNO2 on the neurotoxin gene expression in non-proteolytic C. botulinum. The combination of 2.5% NaCl with 37.5 ppm or 75 ppm NaNO2 resulted in no observed growth of C. botulinum. In addition, 1.25% NaCl in combination with NaNO2 was found to have an inhibitory growth effect of the bacteria. As opposed, the relative bontB expression and the BoNT/B formation remained unchanged. An elevated CO2 concentration was found to have a stimulatory effect on the bontB expression. A 5-fold increase was observed at 70% CO2 atmosphere compared with 10% CO2. This finding was also confirmed when analyzing the BoNT/B formation with ELISA.
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| 7. |
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| 8. |
- Lövenklev, Maria, et al.
(författare)
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Quantitative interaction effects of carbon dioxide, sodium chloride, and sodium nitrite on neurotoxin gene expression in nonproteolytic Clostridium botulinum type B
- 2004
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 70:5, s. 2928-2934
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Tidskriftsartikel (refereegranskat)abstract
- The effects of carbon dioxide, sodium chloride, and sodium nitrite on type B botulinum neurotoxin (BoNT/B) gene (cntB) expression in nonproteolytic Clostridium botulinum were investigated in a tryptone-peptone-yeast extract (TPY) medium. Various concentrations of these selected food preservatives were studied by using a complete factorial design in order to quantitatively study interaction effects, as well as main effects, on the following responses: lag phase duration (LPD), growth rate, relative cntB expression, and extracellular BoNT/B production. Multiple linear regression was used to set up six statistical models to quantify and predict these responses. All combinations of NaCl and NaNO2 in the growth medium resulted in a prolonged lag phase duration and in a reduction in the specific growth rate. In contrast, the relative BoNT/B gene expression was unchanged, as determined by the cntB-specific quantitative reverse transcription-PCR method. This was confirmed when we measured the extracellular BoNT/B concentration by an enzyme-linked immunosorbent assay. CO2 was found to have a major effect on gene expression when the cntB mRNA levels were monitored in the mid-exponential, late exponential, and late stationary growth phases. The expression of cntB relative to the expression of the 16S rRNA gene was stimulated by an elevated CO2 concentration; the cntB mRNA level was fivefold greater in a 70% CO2 atmosphere than in a 10% CO2 atmosphere. These findings were also confirmed when we analyzed the extracellular BoNT/B concentration; we found that the concentrations were 27 ng·ml -1·unit of optical density-1 in the 10% CO 2 atmosphere and 126 ng·ml-1·unit of optical density-1 in the 70% CO2 atmosphere.
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| 9. |
- Lövenklev, Maria, et al.
(författare)
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Relative neurotoxin gene expression in Clostridium botulinum type B, determined using quantitative reverse transcription-PCR
- 2004
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 70:5, s. 2919-2927
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative reverse transcription-PCR (qRT-PCR) method was developed to monitor the relative expression of the type B botulinum neurotoxin (BoNT/B) gene (cntB) in Clostridium botulinum. The levels of cntB mRNA in five type B strains were accurately monitored by using primers specific for cntB and for the reference gene encoding the 16S rRNA. The patterns and relative expression of cntB were different in the different strains. Except for one of the strains investigated, an increase in cntB expression was observed when the bacteria entered the early stationary growth phase. In the proteolytic strain C. botulinum ATCC 7949, the level of cntB mRNA was four- to fivefold higher than the corresponding levels in the other strains. This was confirmed when we quantified the production of extracellular BoNT/B by an enzyme-linked immunosorbent assay and measured the toxicity of BoNT/B by a mouse bioassay. When the effect of exposure to air on cntB expression was investigated, no decline in the relative expression was observed in spite of an 83% reduction in the viable count based on the initial cell number. Instead, the level of cntB mRNA remained the same. When there was an increase in the sodium nitrite concentration, the bacteria needed a longer adjustment time in the medium before exponential growth occurred. In addition, there was a reduction in the expression of cntB compared to the expression of the 16S rRNA gene at higher sodium nitrite concentrations. This was most obvious in the late exponential growth phase, but at the highest sodium nitrite concentration investigated, 45 ppm, a one- to threefold decline in the cntB mRNA level was observed in all growth phases.
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| 10. |
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| 11. |
- Rådström, Peter, et al.
(författare)
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Pre-PCR processing : Strategies to generate PCR-compatible samples
- 2004
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Ingår i: Molecular Biotechnology. - 1073-6085 .- 1559-0305. ; 26:2, s. 133-146
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Tidskriftsartikel (refereegranskat)abstract
- Polymerase chain reaction (PCR) is recognized as a rapid, sensitive, and specific molecular diagnostic tool for the analysis of nucleic acids. However, the sensitivity and kinetics of diagnostic PCR may be dramatically reduced when applied directly to biological samples, such as blood and feces, owing to PCR-inhibitory components. As a result, pre-PCR processing procedures have been developed to remove or reduce the effects of PCR inhibitors. Pre-PCR processing comprises all steps prior to the detection of PCR products, that is, sampling, sample preparation, and deoxyribonucleic acid (DNA) amplification. The aim of pre-PCR processing is to convert a complex biological sample with its target nucleic acids/cells into PCR-amplifiable samples by combining sample preparation and amplification conditions. Several different pre-PCR processing strategies are used: (1) optimization of the DNA amplification conditions by the use of alternative DNA polymerases and/or amplification facilitators, (2) optimization of the sample preparation method, (3) optimization of the sampling method, and (4) combinations of the different strategies. This review describes different pre-PCR processing strategies to circumvent PCR inhibition to allow accurate and precise DNA amplification.
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| 12. |
- Rådström, Peter, et al.
(författare)
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Pre-PCR processing strategies
- 2004
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Ingår i: PCR technology : current innovations. - 0849311845
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- A review describes the sample prepn. for biochem. methods, enrichment methods, immunol. methods, and phys. methods. The pretreatment of a complex biol. sample is crucial, and for successful PCR the following requirements have to be fulfilled: complete lack or low concn. of PCR-inhibitory components in the sample and sufficient concn. of target DNA. The aim of the pre-PCR treatment is to convert a complex biol. sample contg. the target microorganisms into PCR-amplifiable samples.
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