Prophage-mediated modulation of interaction of Streptococcus thermophilus J34 with human intestinal epithelial cells and its competition against human pathogens.

The human intestinal microbiota plays an important role in human health. While adhesion to gastrointestinal mucosa is a prerequisite for colonisation, inhibition of adhesion is a property which may prevent or reduce infections by food borne pathogens. Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus represent the two lactic bacteria constituting the yoghurt culture. These starter cultures have been claimed to be probiotic. In our study we compared two S. thermophilus strains (i.e. lysogenic strain J34 and corresponding non-lysogenic [prophage-cured] strain J34-6), with respect to (1) their in vitro adhesion properties to HT29 cells and (2) their cell surface hydrophobicities. Effects of the two strains on inhibition of adhesion of the pathogens Listeria monocytogenes Scott A, Staphylococcus aureus 6732 and Salmonella enteritidis S489 were studied in vitro with HT29 cell cultures. Lysogenic strain J34 was shown to be considerably more effective than the non-lysogenic derivative strain J34-6.

Boza, a natural source of probiotic lactic acid bacteria.

AIMS: To evaluate the probiotic properties of strains isolated from boza, a traditional beverage produced from cereals. METHODS AND RESULTS: The strains survived low pH conditions (pH 3.0), grew well at pH 9.0 and were not inhibited by the presence of 0.3% (w/v) oxbile. Cytotoxicity levels of the bacteriocins, expressed as CC(50), ranged from 38 to 3776 microg ml(-1). Bacteriocin bacST284BZ revealed high activity (EC(50) = 735 microg ml(-1)) against herpes simplex virus type 1. Growth of Mycobacterium tuberculosis was 69% repressed after 5 days in the presence of bacST194BZ. Various levels of auto-cell aggregation and co-aggregation with Listeria innocua LMG 13568 were observed. Adhesion of the probiotic strains to HT-29 cells ranged from 18 to 22%. CONCLUSIONS: Boza is a rich source of probiotic lactic acid bacteria. All strains survived conditions simulating the gastrointestinal tract and produced bacteriocins active against a number of pathogens. Adherence to HT-29 and Caco-2 cells was within the range reported for Lactobacillus rhamnosus GG, a well-known probiotic. In addition, the high hydrophobicity readings recorded define the strains as good probiotics. SIGNIFICANCE AND IMPACT OF THE STUDY: Boza contains a number of different probiotic lactic acid bacteria and could be marketed as a functional food product.

[The combination effects of quercetin with the herbicides atrazine, cyanazine and gesamprim in mutagenicity tests]. / Prüfung auf Kombinationseffekte von Quercetin mit den Herbiziden Atrazin, Cyanazin und Gesamprim in Mutagenitätstests.

The plant flavonol quercetin and the triazine herbicides atrazine, cyanazine, and gesamprim were examined individually and in combination for the induction of genotoxic effects. The sister chromatid exchange (SCE) assay and the gene mutation assay for 6-thioguanine resistance (HPRT) were carried out with Chinese hamster ovary (CHO) cells. Whereas no evidence of an increased SCE rate was found, the test substances caused a slightly increased mutation rate in the HPRT assay after metabolic activation with a subcellular liver enzyme preparation. Combination studies with two or three of the test substances did not result in higher mutation rates than those observed for the individual compounds tested singly.

Assessment of genotoxic effects by lindane.

The well known and previously widespread insecticide lindane has been re-assessed for DNA-damaging activity. A first group of investigations using standard in vitro and in vivo mutagenicity assays did not indicate any genotoxic effects of lindane at all. The assay systems used were for the induction of HPRT mutations and sister chromatid exchanges in CHO cells cultured in vitro, and for micronuclei induction in vivo in bone marrow cells of rats, hamsters and mice. Also, lindane was assessed for its potential to induce sister chromatid exchanges in vivo in the bone marrow of Chinese hamsters. These specific assay systems had not been used previously for elucidating the genotoxic effects of this compound, but they are basically similar to other standard mutagenicity assays in which lindane has been shown to be devoid of genotoxic activity. The second part of the investigations was directed at re-evaluating a previously reported positive effect of the compound in primary rat hepatocytes in vitro. We performed in vitro and in vivo studies with hepatocytes from the rat liver and used alkaline elution to detect DNA damage. However, we could not demonstrate that lindane induced genotoxicity, unless considerable concomitant cytotoxicity was apparent as well. Finally, since lindane can be ingested and inhaled by humans, we also measured the induction of DNA damage in local target organs of absorption using single cell micro-gel-electrophoresis (the comet assay). In these cases lindane was genotoxic in cells of the gastric and nasal mucosa in vitro and also in vivo following appropriate routes of application (oral and inhalational exposure).

Re-examination of potassium sorbate and sodium sorbate for possible genotoxic potential.

Potassium sorbate and sodium sorbate were investigated for possible genotoxic actions using the Salmonella/mammalian-microsome test, HGPRT and sister chromatid exchange (SCE) test with Chinese hamster ovary cells, the micronucleus test on bone marrow cells of mice and Chinese hamsters, and the chromosome aberration and SCE test on Chinese hamsters. In all the in vitro tests no signs of genotoxicity were detected. Whereas no in vivo mutagenicity of potassium sorbate and sodium sorbate with freshly prepared aqueous solutions and with stored potassium sorbate was found, investigations with stored sodium sorbate revealed weak clastogenic activity by increased chromosome aberrations and elevated numbers of micronuclei at doses of 200 mg/kg body weight, but no induction of SCEs.