[Host-pathogen relations in yeasts]. / Wirt-Erreger-Beziehungen bei Hefen.

Allogenic and autogenic factors are decisive for a colonization of warmblooded hosts by yeasts where they can live inside as symbiont, commensal or pathogen. To develop pathogenicity a capacity of yeasts for multiplication inside of humans or homoiothermic animals and resistance to environmental influences is not sufficient. Pathogenicity rather depends on the ability of structural morphological changes, phenomena of adherence and of microbial competition as well as the presence of genes for down-regulation of the host defense and for enzyme production enabling a parasitic life style. Among the yeasts Cryptococcus neoformans and some Candida species meet these requirements.

Adherence of Escherichia coli serogroup O 157 and the Salmonella typhimurium mutant DT 104 to the surface of Saccharomyces boulardii.

The detection of lectin sites for mannose-sensitive adhesion in the outer membrane of Saccharomyces boulardii and the irreversible binding of both enteropathogenic Escherichia coli (EPEC) and salmonellae (serovar Salmonella Typhimurium and Salmonella Enteritidis) provided the motivation to carry out further investigations to find out whether also other enteric bacteria such as entero-haemorrhagic Escherichia coli (EHEC) and the DT 104 mutant of S. Typhimurium have the capacity for binding to the cell wall of this yeast. Reference strains and fresh isolates from clinical cases of EHEC infections as well as salmonellae of the DT 104 mutant were included in this study using the agglutination test. The results first of all showed that EHEC of the serogroup O 157 and the DT 104 mutant of S. Typhimurium were bound to the surface of Saccharomyces boulardii. Because these bacteria do not respond very well to drugs but most of the gastrointestinal infections are caused by them, the use of S. boulardii for treatment and prophylaxis could be an excellent alternative.

[Health risks of mycotoxins for humans]. / Gesundheitsgefährdung des Menschen durch Mykotoxine.

Fungi cause diseases in humans in different ways. Due to production of secondary metabolites by molds, dematiaceous hyphomycetes, and primary plant pathogenic fungus species intoxications are included in their pathogenic potency. Mycotoxins mostly enter the body by ingestion of food because they are contaminants of plant products and in case of carry over also of animal products. Recent investigations have shown that mycotoxins detected in feed and food during microbial deterioration can also be produced inside warm-blooded organism, e. g. with aspergillosis in animals (mammals and birds). This means an enhanced risk for humans to suffer from mycotoxicosis, in which the toxic agent has an exogenic or endogenic source. Therefore, attention should be paid to the fact that mycotoxins are not only damaging cells; they very often possess a genotoxic potential.

[Regulation of the intestinal flora by food]. / Regulierung der Darmflora über die Nahrung.

The purpose of probiotics is to regulate the bacterial colonisation of the digestive tract. In contrast to antibiotics, with the probiotics it is not a certain metabolic product of bacteria or fungi with a known spectrum of antimicrobial activity which, for example when used as performance enhancers under the conditions permitted according to the EEC guidelines for feed additives, reduce the numbers of bacteria, which appear in the small intestines of domestic animals and compete with the host for nutrients and vitamins, but there it is rather the living micro-organisms themselves which are intended to, to help to improve the performance of domestic animals on the basis of a fundamentally different mechanism of action. Recent findings on the effect of the phenomena of bacterial competition on the processes of an infection, with penetration, adhesion, and multiplication as prerequisites for development of the parasitic mechanism of a pathogen, have shown that by controlling the processes of colonization of the intestines with micro-organisms and also their metabolic activity it is possible to at least reduce the incidence of the diarrhoeal diseases which are responsible for the the greatest economic damage. The numerical displacement of bacterial pathogens is not the only effect of the bacterial competition resulting from the orally administered micro-organisms. The fact that antagonistically acting bacteria or yeasts prevent the pathogenic species from entering the intestinal epithelial cells plays a role here. As a result of which, especially the small intestines are not colonized by pathogens (E. coli and others), the liver is largely relieved of substances accumulating in the course of bacterial protein metabolism, the absorption of fatty acids and other energy-providing compounds is increased, and not readily soluble salts are transformed into soluble compounds. Effects comparable to those obtained with small amounts of antibiotics added to the feed of farm animals as regards increased growth rate and improved feed conversion, can also achieved with the addition of probiotics.