Characterization of pathogenic Escherichia coli isolated from humans in Austria: phenotypes, toxin gene types and epidemiology.

One hundred and ten clinical Escherichia coli isolates of serovar O157 (n = 102) and O26 (n = 8) were characterized for the presence of putative virulence genes by PCR. All but one of these isolates contained the eae gene. The EHEC-hly gene could be detected in all E. coli O157 and in 50% of E. coli O26 isolates. Forty-five (40.9%) of the 110 E. coli were positive for both stx(1) and stx(2) genes, 2 (1.8%) isolates were positive for stx(1) and 57 isolates (51.8%) were positive for stx(2) only. Among the 102 stx(2) positive isolates, 14 (13.7%) E. coli O157 contained also the stx(2c) variant gene. No other stx(2) variant was identified. Six clinical isolates (five E. coli O157:H7 and one E. coli O26) did not contain stx genes. Ten non-pathogenic E. coli isolates which were amplified as controls didn't contain any stx and eae gene but two of the ten strains contained the EHEC-hly gene. By their growth on chromogenic media, all but two of 50 E. coli O157 could be differentiated from eight E. coli O26 and 10 non-pathogenic E. coli. Sixty-one of the O157:H7 isolates were further subjected to pulsed-field gel electrophoresis (PFGE) which identified 49 distinguishable patterns. In five cases where contact infection among family members was suspected, indistinguishable PFGE patterns confirmed the epidemiological relatedness of the isolates. Moreover, two PFGE clusters were identified which comprised five and three strains, respectively. These findings indicate the occurrence of both family and diffuse outbreaks of E. coli O157 infections in Austria during recent years and demonstrate the need for molecular subtyping of these pathogens.

Model studies on the detectability of genetically modified feeds in milk.

Detecting the use of genetically modified feeds in milk has become important, because the voluntary labeling of milk and dairy products as "GMO free" or as "organically grown" prohibits the employment of genetically modified organisms (GMOs). The aim of this work was to investigate whether a DNA transfer from foodstuffs like soya and maize was analytically detectable in cow's milk after digestion and transportation via the bloodstream of dairy cows and, thus, whether milk could report for the employment of transgene feeds. Blood, milk, urine, and feces of dairy cows were examined, and foreign DNA was detected by polymerase chain reaction by specifically amplifying a 226-bp fragment of the maize invertase gene and a 118-bp fragment of the soya lectin gene. An intravenous application of purified plant DNA showed a fast elimination of marker DNA in blood or its reduction below the detection limit. With feeding experiments, it could be demonstrated that a specific DNA transfer from feeds into milk was not detectable. Therefore, foreign DNA in milk cannot serve as an indicator for the employment of transgene feeds unless milk is directly contaminated with feed components or airborne feed particles.

Influence of a probiotic yoghurt on the status of vitamins B(1), B(2) and B(6) in the healthy adult human.

BACKGROUND/AIMS: The main reason for this study was to determine whether yoghurt bacteria, being rich in some water-soluble vitamins, release them or utilize vitamins from their surroundings. Our study was trying to determine for the first time, if the viable bacteria of probiotic yoghurt are able to influence the parameters of the B-vitamin (B(1), B(2), B(6)) status of the healthy adult human. METHODS: The test yoghurt was commercially available probiotic yoghurt prepared with Streptococcus thermophilus and Lactobacillus acidophilus, enriched with Lactobacillus casei GG. Different chemical forms of all investigated B-vitamins were determined by HPLC methods. In order to determine the influence of the yoghurt flora, each of 12 subjects consumed four yoghurt portions 125 g each ( = 500 g) a day, containing thermally inactivated cultures during the first 2-week period and yoghurt without heat treatment during the second 2-week period. RESULTS: The heat treatment of the probiotic yoghurt caused negligible changes in vitamin contents. The plasma levels of thiamin decreased significantly (p < 0.01) after the first 2-week period and kept on decreasing during the second 2-week period. A similar trend was found in the urinary excretion. The plasma levels of the B(2)-vitamers were different. The flavin adenine dinucleotide concentrations increased significantly (p < 0.01) after the consumption of heat-treated yoghurt and decreased significantly (p < 0.05) after the following 2 weeks, in which the subjects received the untreated yoghurt. In contrast, the flavin mononucleotide plasma levels decreased during the first 2-week period and increased during the second part of the study, but the change was not statistically significant. The free riboflavin concentrations in plasma and urine showed a continuous but not significant increase. The concentrations of pyridoxal-5-phosphate in plasma increased after the consumption of yoghurt with the inactivated bacteria and decreased in the second part of the study. However, the differences were not significant. The excretion of thiamin, B(2)- and B(6)-vitamers in the faeces did not significantly change throughout the study period (p>0.05). CONCLUSIONS: Our observations show that the bacterial flora of the examined yoghurt does not influence the vitamin B(1), B(2) and B(6) status of man. It seems likely that even lactobacilli of the 'probiotic' type which are vitamin B consumers can decrease the bioavailability of these vitamins for man. Obviously a thermal death of the cells did not induce a release of physiologically active vitamins.

Aminopeptidase from Brevibacterium linens: activation and inhibition.

Activation and inhibition of a purified aminopeptidase from Brevibacterium linens was investigated using L-alpha-leucyl-4-nitroanilide and L-leucyl-L-leucine as substrates. The enzyme was activated by cobalt, provided that the enzyme was preincubated with the metal. Strong inhibitory effects were derived from heavy metals, metal-complexing compounds, reducing agents, the modification of aromatic amino acids, and the presence of hydrophobic substances or certain amino acids in the test mixtures. Supposing that this B. linens aminopeptidase plays a part during surface-ripening of cheeses, possible consequences of specific technological conditions for its activity are discussed.