Biomedical subjects

A von Wright

Publications and source records attributed to A von Wright.

At least 19 recordsLinked to original sources

PubMed2005

Occurrence of virulence factors among human intestinal enterococcal isolates.

AIMS: The aim of this study was to investigate the frequency of enterococcal virulence factors among human intestinal Enterococcus faecalis strains and to find out whether the pattern differs from that seen in published reports on food and clinical isolates. METHODS AND RESULTS: The E. faecalis isolates were cultured from human faecal samples obtained from five ulcerative colitis patients in remission phase. The species identification was based on API120 strips and species-specific PCR primers. The isolates were further characterized using the pulsed-field gel electrophoresis. The presence of seven different known enterococcal virulence factors among the confirmed E. faecalis isolates were screened using PCR techniques and published primers. CONCLUSIONS: Among the 35 isolates representing nine different pulsotypes the most frequent virulence factors were cpd (33 isolates), agg (25 isolates), gelE (22 isolates) and esp (15 isolates). No complete sets of genes associated for the production of functional cytolysin were encountered indicating that intestinal enterococci may differ in this respect from clinical strains. SIGNIFICANCE AND IMPACT OF THE STUDY: According to the results, the commensal enterococcal strains appear to differ from clinical isolates in their complement of presumed virulence factors.

Adult↗

PubMed2004

The relevance of gene transfer to the safety of food and feed derived from genetically modified (GM) plants.

In 2000, the thematic network ENTRANSFOOD was launched to assess four different topics that are all related to the testing or assessment of food containing or produced from genetically modified organisms (GMOs). Each of the topics was linked to a European Commission (EC)-funded large shared cost action (see http://www.entransfood.com). Since the exchange of genetic information through horizontal (lateral) gene transfer (HGT) might play a more important role, in quantity and quality, than hitherto imagined, a working group dealing with HGT in the context of food and feed safety was established. This working group was linked to the GMOBILITY project (GMOBILITY, 2003) and the results of the deliberations are laid down in this review paper. HGT is reviewed in relation to the potential risks of consuming food or feed derived from transgenic crops. First, the mechanisms for obtaining transgenic crops are described. Next, HGT mechanisms and its possible evolutionary role are described. The use of marker genes is presented in detail as a special case for genes that may pose a risk. Furthermore, the exposure to GMOs and in particular to genetically modified (GM) deoxyribonucleic acid (DNA) is discussed as part of the total risk assessment. The review finishes off with a number of conclusions related to GM food and feed safety. The aim of this paper is to provide a comprehensive overview to assist risk assessors as well as regulators and the general public in understanding the safety issues related to these mechanisms.

Animal Feed↗

PubMed2001

Lactobacillus crispatus and its nonaggregating mutant in human colonization trials.

A wild-type Lactobacillus crispatus, showing a cell aggregation phenotype and its spontaneous nonaggregating mutant were compared for their in vitro adhesion properties to human ileal mucus and to a cultured human colonic cell line (Caco2) and for their in vivo colonization and adhesion potential with colonoscopy patients as volunteers in feeding trials. The wild-type strain adhered better to mucus or to Caco2 cells than did the mutant. Altogether, three human trials with the wild type and two with the mutant strain were performed. In two of the trials, the wild type could be recovered from either fecal samples or biopsies taken from the colon, while the mutant strain could not be demonstrated in either of the trials where it was used. The L. crispatus colonies recovered from the trials were often mixed, and several enterococci and lactobacillus strains coaggregating with L. crispatus wild type could be isolated. The results indicate that the surface-mediated properties, such as aggregation, of lactobacilli can have a role in adhesion and colonization.

Bacterial Adhesion↗

PubMed2001

Fish quality assessment with ion mobility based gas detector.

Measurement of the mixture of extractable volatile compounds of the gills of vendace was used in the fish freshness evaluation (Coregonus albula L.). MGD-1 gas detector was used for the detection of volatile compound profiles of hexane extracts of gills. The measuring principle of MGD-1 is ion mobility distribution and is based on IMCELL technique. A 2.5 microl sample of hexane extract was heated on a ceramic plate and the vapour was carried with a constant flow (2.5 I/min) of active carbon filtered air to the detector. The ion mobility distribution spectrum was measured every 1 second for 2 minutes. For reference, the microbial counts of gills, ATP-breakdown products (K-value) of fish flesh, electrical properties (Torrymeter scores) of fish skin and sensory evaluation scores were measured. The ion mobility distribution profiles of gills changed significantly during the 7 days storage period The findings related to freshness evaluation were supported by the reference methods. There is, however, a seasonal difference in the freshness probably due to seasonal variation of microbial flora. Besides the evaluation of fish quality, ion mobility distribution based technique provides a new analytical tool for food quality assessment.

Animals↗

PubMed1999

The effect of probiotic strains on the microbiota of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME).

The aim of the present work was to study five potential probiotic strains (Lactobacillus plantarum, two strains of L. paracasei subsp. paracasei, L. rhamnosus and Bifidobacterium sp.) comparatively in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME) in vitro model, and to evaluate this model as a tool in the screening and selection of probiotic bacteria. The impact of the strains on the composition of microbiota and its metabolic activities (production of lactic acid and short-chain fatty acids) was studied. Changes in composition of the microbiota become apparent as a result of probiotic treatment. A marked, but temporary, increase was noted in the number of lactic acid bacteria and bifidobacteria. The profiles of D(-) and L(+) isomers of lactic acid detected in the SHIME after addition of probiotic strains corresponded well to those that are produced in pure culture conditions. The numbers of enterobacteriaceae decreased markedly and those of clostridia detectably during the intervention, while the enterococci tended to increase after the treatment. This pattern was similar in the reactors representing both the small and large intestine in the model. The changes in short-chain fatty acids were small, and no definite trend was observed.

Bifidobacterium↗

PubMed1999

Toxicity of selected plant volatiles in microbial and mammalian short-term assays.

In this study, several short-term microbial and mammalian in vitro assays were used to evaluate cytotoxicity and genotoxicity of four plant volatiles showing antifungal activity: cinnamaldehyde, carvacrol, thymol and S(+)-carvone. All inhibited viability and proliferation of Hep-2 cells in a dose-dependent manner. IC50 ranged from 0.3 mM (cinnamaldehyde) to 0.7 mM (thymol) in viability tests and from 0.2 mM (carvacrol) to 0.9 mM (carvone) in the proliferation test. The morphological analysis suggested an involvement of apoptosis in the cases of carvone, carvacrol and cinnamaldehyde. At nontoxic doses, carvacrol and thymol increased the number of revertants in the Ames test by 1.5-1.7 times, regardless of metabolic activation. In the SOS-chromotest, none of the four plant volatiles caused DNA damage at non-toxic doses. In the DNA repair test, a marked dose-dependent differential toxicity was observed with carvone and, to a lesser extent, with cinnamaldehyde, while with thymol and carvacrol, this effect was less pronounced. In conclusion, the considered in vitro cytotoxicity assays have shown to be sensitive enough to highlight a variety of toxic effects at the cellular level, which can be rather different between chemically closely related compounds, such as isomers.

Acrolein↗

PubMed1999

Persistence of colonization of human colonic mucosa by a probiotic strain, Lactobacillus rhamnosus GG, after oral consumption.

Lactobacillus rhamnosus GG is one of the most thoroughly studied probiotic strains. Its advantages in the treatment of gastrointestinal disorders are well documented. The aim of the present study was to demonstrate with colonic biopsies the attachment of strain GG to human intestinal mucosae and the persistence of the attachment after discontinuation of GG administration. A whey drink fermented with strain GG was fed to human volunteers for 12 days. Fecal samples were collected before, during, and after consumption. L. rhamnosus GG-like colonies were detected in both fecal and colonic biopsy samples. Strain GG was identified by its characteristic colony morphology, a lactose fermentation test, and PCR. This study showed that strain GG was able to attach in vivo to colonic mucosae and, although the attachment was temporary, to remain for more than a week after discontinuation of GG administration. The results demonstrate that the study of fecal samples alone is not sufficient in evaluating colonization by a probiotic strain.

Administration, Oral↗

PubMed1999

Probiotics: established effects and open questions.

Human intestinal microflora is a complex ecosystem with hundreds of bacterial species. Its metabolic functions and interactions with the host probably affect the human health and well being, but these effects are extremely difficult to study. However, for about 100 years, the idea of modifying the composition of colonic flora by consuming viable bacteria in order to improve the quality of life and to prevent and treat intestinal disorders has had some popularity. Solid clinical data have usually been lacking to support the health claims associated with these so-called probiotics. The situation, however, is rapidly changing. Competent clinical studies are accumulating, showing that specific probiotic microbes, mainly lactic acid bacteria and bifidobacteria, can alleviate or prevent diverse intestinal disorders and reduce the risk of some intestinal diseases. Some indication of the mechanisms of action can also be deduced from the data available, while rapidly developing molecular biological methods offer new tools to verify the survival of the probiotics in the gut and the subsequent adhesion to mucosae. While development of foods containing probiotic bacteria has a great potential for the food industry and can be expected to positively affect the general health of the population, safety considerations have to be taken into account while introducing new species or strains without a previous history of safe food use.

Bifidobacterium↗

PubMed1998

Detection of beer spoilage bacteria Megasphaera and Pectinatus by polymerase chain reaction and colorimetric microplate hybridization.

Anaerobic bacteria of the genera Megasphaera and Pectinatus cause beer spoilage by producing off flavours and turbidity. Detection of these organisms is complicated by the strict anaerobic conditions and lengthy incubation times required for their cultivation, consequently there is a need for more rapid detection methods. A polymerase chain reaction (PCR) method and a colorimetric microplate hybridization assay were developed for the rapid and specific detection of Megasphaera cerevisiae and Pectinatus spp. A biotinylated primer pair was designed for the amplification of a 403 base pair (bp) fragment of the M. cerevisiae 16S rRNA gene and a primer pair from literature was used for the amplification of an 816 bp fragment of Pectinatus 16S rRNA gene. Amplified PCR products were analyzed by the colorimetric microplate hybridization method in which a biotinylated PCR product was captured by streptavidin and hybridized with a digoxigenin-labelled oligonucleotide probe. In the final step an enzyme-linked antibody and a colorimetric reaction were utilized. A simple and rapid sample treatment was set up for the PCR detection of contaminants in beer. Detection of M. cerevisiae (> or = 5 x 10(3) colony forming units [cfu]/100 ml) and Pectinatus frisingensis (> or = 5 x 10(5) cfu/100 ml) in beer was successful, but the sensitivity of the assay still needs to be improved for direct detection of the small amounts of bacteria present in beer.

Beer↗

PubMed1998

Oat bran beta-gluco- and xylo-oligosaccharides as fermentative substrates for lactic acid bacteria.

The influence of oat bran oligosaccharides on carbohydrate utilization and fermentation end-products was studied with reference to three different lactic acid bacteria (LAB: Lactobacillus rhamnosus, Lactobacillus plantarum and Lactococcus lactis). The main results were that all three LAB utilized oat beta-gluco-oligosaccharides, while only L. plantarum utilized xylo-oligosaccharides. The main products of LAB metabolism were lactic acid, acetic acid, formic acid and ethanol. The results indicated that oat beta-gluco-oligosaccharides and xylo-oligosaccharides induce LAB to form the end-products of a typical mixed-acid fermentation. The formation of mixed-acid production from xylo-oligosaccharides was mainly due to the starvation of cells. This study indicates that oat bran oligosaccharides affect both qualitatively and quantitatively the fermentation end-products of LAB grown on these substrates. This should be taken into account when selecting strains for new fermented cereal based food products.

Acetic Acid↗

PubMed1998

Demonstration of safety of probiotics -- a review.

Probiotics are commonly defined as viable microorganisms (bacteria or yeasts) that exhibit a beneficial effect on the health of the host when they are ingested. They are used in foods, especially in fermented dairy products, but also in pharmaceutical preparations. The development of new probiotic strains aims at more active beneficial organisms. In the case of novel microorganisms and modified organisms the question of their safety and the risk to benefit ratio have to be assessed. Lactic acid bacteria (LAB) in foods have a long history of safe use. Members of the genera Lactococcus and Lactobacillus are most commonly given generally-recognised-as-safe (GRAS) status whilst members of the genera Streptococcus and Enterococcus and some other genera of LAB contain some opportunistic pathogens. Lactic acid bacteria are intrinsically resistant to many antibiotics. In many cases resistances are not, however, transmissible, and the species are also sensitive to many clinically used antibiotics even in the case of a lactic acid bacteria- associated opportunistic infection. Therefore no particular safety concern is associated with intrinsic type of resistance. Plasmid-associated antibiotic resistance, which occasionally occurs, is another matter because of the possibility of the resistance spreading to other, more harmful species and genera. The transmissible enterococcal resistance against glycopeptide antibiotics (vancomycin and teicoplanin) is particularly noteworthy, as vancomycin is one of the last effective antibiotics left in the treatment of certain multidrug-resistant pathogens. New species and more specific strains of probiotic bacteria are constantly identified. Prior to incorporating new strains into products their efficacy should be carefully assessed, and a case by case evaluation as to whether they share the safety status of traditional food-grade organisms should be made. The current documentation of adverse effects in the literature is reviewed. Future recommendations for the safety of already existing and new probiotics will be given.

Animals↗

PubMed1998

The colonization of a simulator of the human intestinal microbial ecosystem by a probiotic strain fed on a fermented oat bran product: effects on the gastrointestinal microbiota.

The effects of Lactobacillus-GG-fermented oat bran product on the microbiota and its metabolic activity in the human gut were investigated, using a simulator of the human intestinal microbial ecosystem (SHIME), by analysing the bacterial population, shortchain fatty acids and gas production. In addition, the effects of fermented oat bran supernatant and supernatant samples from reactors 4, 5 and 6 (large intestine) on the growth of Escherichia coli IHE 13047, Enterococcus faecalis VTT E-93203, Lactobacillus rhamnosus VTT E-94522 (Lactobacillus GG) and Lactococcus lactis subsp. lactis VTT E-90414 were monitored to ascertain possible stimulatory/inhibitory effects by an in vitro turbidometric method. Our experiments showed that Lactobacillus GG colonized the SHIME reactor and this colonization could be maintained for several weeks without extra supplementation. Oat bran feeding also favoured the growth of bifidobacteria and caused an increase in the production of acetic, propionic and butyric acid as well as CH4 and CO2. However, the effects of oat bran, either on bacterial populations or on their metabolic activity, were not directly dose-dependent. In turbidometric measurements, the supernatant of fermented oat bran exerted an inhibitory effect of Lactobacillus GG, but stimulated the growth of enterococci.

Avena↗

PubMed1997

Comparison of the lethal effects of different actinomycins on a repair-deficient strain of Escherichia coli.

We report here the isolation and purification of a genotoxic antibiotic from the culture medium of a Streptomyces strain. The antibiotic was identified as actinomycin X2 by using a database search (AntiBase). In the previous studies a related compound, actinomycin D, has been shown to be non-mutagenic in the salmonella/microsome assay and several other bacterial systems. The fact that an actinomycin was detected by a bacterial repair assay seems to contradict these results. Therefore we tested several actinomycins by differential killing assay based on the same Escherichia coli strains that were used in our screening bioassays. According to our results the uvrA, recA double mutant sensitizes E. coli to the genotoxic effects of actinomycins.

Adenosine Triphosphatases↗

PubMed1997

Replication regions of two pairs of incompatible lactococcal theta-replicating plasmids.

Incompatibility tests were performed employing 12 replicons belonging to a family of homologous lactococcal theta-replicating plasmids. Two pairs of incompatible plasmids were found, namely, pFV1001 and pFV1201, and pJW565 and pFW094. The replicons of plasmids pFV1001, pFV1201, pJW565, pJW566, and pFW094 were sequenced. Alignments were made of the replicational origins (repA) and putative replication proteins (RepB) of these and 11 related plasmid sequences. Comparison of the alignments with the incompatibility data indicated that the incompatibility determinant could be contained within the 22-bp tandem repeats DRII and/or the inverted repeat IR1 in repA. In support, the incompatibility determinant of pJW563 was localized to a 743-bp fragment encompassing repA. A stretch of 13 amino acids of RepB was proposed to be responsible for the plasmid-specific initiation of replication. This stretch is part of a domain containing features that are highly conserved within the proposed DNA binding regions of the initiation proteins from several well-characterized plasmids from Gram-negative bacteria, including pSC101, R6K, and mini-F.

Amino Acid Sequence↗

PubMed1997

Bacterial degradation of styrene in waste gases using a peat filter.

A biofiltration process was developed for styrene-containing off-gases using peat as filter material. The average styrene reduction ratio after 190 days of operation was 70% (max. 98%) and the mean styrene elimination capacity was 12 g m-3 h-1 (max. 30 g m-3 h-1). Efficient styrene degradation required addition of nutrients to the peat, adjustment of the pH to a neutral level and efficient control of the humidity. Maintenance of the water balance was easier in a down-flow than in an up-flow process, the former consequently resulting in much better filtration efficiency. The optimum operation temperature was around 23 degrees C, but the styrene removal was still satisfactory at 12 degrees C. Seven different bacterial isolates belonging to the genera Tsukamurella, Pseudomonas, Sphingomonas, Xanthomonas and an unidentified genus in the gamma group of the Proteobacteria isolated from the microflora of active peat filter material were capable of styrene degradation. The isolates differed in their capacity to decompose styrene to carbon dioxide and assimilate it to biomass. No toxic intermediate degradation products of styrene were detected in the filter outlet gas or in growing cultures of isolated bacteria. The use of these isolates in industrial biofilters is beneficial at low styrene concentrations and is safe from both the environmental and public health points of view.

Biodegradation, Environmental↗

PubMed1997

Recovery of Lactobacillus rhamnosus GG from human colonic biopsies.

The colonization of Lactobacillus rhamnosus GG (ATCC 53103, henceforth L.GG) in five human colonoscopy patients was studied. The test subjects consumed whey drink fermented with the bacterium for 12 d before the colonoscopy. The presence of L.GG was subsequently checked both in the faecal samples and in the colonic biopsies obtained from various locations in the large intestine. In all patients L.GG was the dominant faecal lactic acid bacterium as a result of the administration. In four patients L.GG could also be recovered from the biopsies, while with one patient (suffering from ulcerative colitis diagnosed during the colonoscopy) no L.GG was detected in the biopsy samples. The results suggest that L.GG is able to adhere in vivo to the colon. Study of the faecal samples alone is apparently not sufficient for elucidation of the gastrointestinal ecology of probiotic bacteria.

Adult↗

PubMed1996

Genotoxicity of dihydroabikoviromycin, a secondary metabolite of Streptomyces anulatus.

The potential genotoxicity of dihydroabikoviromycin was assessed in bacterial and sister-chromatid exchange (SCE) test systems. Direct cytotoxicity was also assayed using bioluminescence methods to screen for differences in cell viability among different tumour cell lines following exposure to the drug. Differential killing tests with Escherichia coli WP2 and its repair-deficient derivative CM871 indicated that a functional DNA repair system was protective against the action of dihydroabikoviromycin, implying that this compound causes some form of DNA damage and is almost certainly therefore genotoxic. Dose-dependent reversion from His- to His+ with dihydroabikoviromycin was observed in the Ames test with Salmonella typhimurium TA100, but not in frameshift tester strain TA98. Dihydroabikoviromycin also induced the sfiA gene, as indicated by beta-galactosidase induction in an SOS-chromotest with E. coli PQ37 strain. A dose-related increase in SCEs by dihydroabikoviromycin was observed in CHO cells. Growth of tumour cells was also suppressed by dihydroabikoviromycin at a dose of 10 micrograms/ml.

Animals↗

PubMed1996

Rapid detection and isolation of DNA-binding compounds from Streptomyces xanthochromogenes.

The culture medium of Streptomyces xanthochromogenes JH903 was found to show selective activity against DNA-repair-deficient Escherichia coli CM871 strain. In this report we describe a simple method to locate and isolate DNA binding compounds from the fermentation broth. The method is based on the retention of DNA-reacting compounds in cellulose complexed with DNA, and purification of these compounds with thin-layer chromatography. Screening of microbial metabolites from chloroform extracts of fermentation media resulted in detection of five genotoxic fractions.

DNA↗