ABSTRACTIncreased microvascular permeability is a hallmark of sepsis and septic shock. Intestinal mucosal dysfunction may allow translocation of bacteria and their products, thereby promoting sepsis and inflammation. AlthoughStaphylococcus aureusalpha-toxin significantly contributes to sepsis and perturbs the endothelial barrier function, little is known about possible effects ofS. aureusalpha-toxin on human epithelial barrier functions. We hypothesize thatS. aureusalpha-toxin in the blood can impair the intestinal epithelial barrier and thereby facilitate the translocation of luminal bacteria into the blood, which may in turn aggravate a septic condition. Here, we showed that staphylococcal alpha-toxin disrupts the barrier integrity of human intestinal epithelial Caco-2 cells as evidenced by decreased transepithelial electrical resistance (TER) and reduced cellular levels of junctional proteins, such as ZO-1, ZO-3, and E-cadherin. The Caco-2 cells also responded to alpha-toxin with an elevated cytosolic calcium ion concentration ([Ca2+]i), elicited primarily by calcium influx from the extracellular environment, as well as with a significant reduction in TER, which was modulated by intracellular calcium chelation. Moreover, a significantly larger reduction in TER and amounts of the junctional proteins,viz., ZO-3 and occludin, was achieved by basolateral than by apical application of the alpha-toxin. These experimental findings thus support the hypothesis that free staphylococcal alpha-toxin in the bloodstream may cause intestinal epithelial barrier dysfunction and further aggravate the septic condition by promoting the release of intestinal bacteria into the underlying tissues and the blood.

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The cause of diarrheal disease is usually determined by screening for several microorganisms by various methods, and sole detection is used to assign the agent as the cause of disease. However, it has become increasingly clear that many infections are caused by coinfections with several pathogens and that the dose of the infecting pathogen is important. We quantified the absolute numbers of enterotoxigenic E. coli (ETEC) and Vibrio cholerae directly in diarrheal fluid. We noted several events where both pathogens were found but also a large dose dependency. In three samples, we found ETEC as the only pathogen sought for. These isolates belonged to globally distributed ETEC clones and were the dominating species in stool with active toxin expression. This suggests that certain superior virulent ETEC lineages are able to outcompete the gut microbiota and be the sole cause of disease and hence need to be specifically monitored.

Enterococcus faecium and Streptococcus gallolyticus subsp. gallolyticus (S. gallolyticus) were classically clustered into the Lancefield Group D streptococci and despite their taxonomic reclassification still share a similar genetic content and environment. Both species are considered as opportunistic pathogens. E. faecium is often associated with nosocomial bacteraemia, and S. gallolyticus is sporadically found in endocarditis of colorectal cancer patients. In both cases, the source of infection is commonly endogenous with a translocation process that launches through the intestinal barrier. To get new insights into the pathological processes preceding infection development of both organisms, we used an in vitro model with Caco-2 cells to study and compare the adhesion, invasion and translocation inherent abilities of 6 E. faecium and 4 S. gallolyticus well-characterized isolates. Additionally, biofilm formation on polystyrene, collagen I and IV was also explored. Overall results showed that E. faecium translocated more efficiently than S. gallolyticus, inducing a destabilization of the intestinal monolayer. Isolates Efm106, Efm121 and Efm113 (p < .001 compared to Ef222) exhibited the higher translocation ability and were able to adhere 2–3 times higher than S. gallolyticus isolates. Both species preferred the collagen IV coated surfaces to form biofilm but the S. gallolyticus structures were more compact (p = .01). These results may support a relationship between biofilm formation and vegetation establishment in S. gallolyticus endocarditis, whereas the high translocation ability of E. faecium high-risk clones might partially explain the increasing number of bacteraemia.

Aim: To investigate the ability of lactobacilli to persist in the genital area (vagina and labia) of women after the topical application of an ointment containing Lactobacillus gasseri LN40, L. fermentum LN99 and L. rhamnosus LN113. Secondary objectives were to study the presence of Escherichia coli and other contaminants, as well as subjective symptoms in the genital tract. Methods: Eighteen healthy postmenopausal women were randomized to use either the study product or placebo for 10 days. Gynecological examinations, labial and vaginal samplings for bacterial cultivation were performed at baseline (visit 1), after treatment (visit 2), and at a 10-day follow-up (visit 3). LN strains were identified by specific cultivation methods. Subjective symptoms were evaluated by a self-administered questionnaire. Results: The presence of LN99 was shown in 7 out of 8 women in the investigational group at visit 2 (p < 0.001 compared to placebo) and in 5 out of 8 at visit 3 (p < 0.05), whereas the presence of LN113 was shown in 2 out of 8 at visit 2 and in 1 out of 8 at visit 3. Subjective symptoms were significantly reduced (p < 0.01) at visits 2 and 3 for both products. Conclusion: Topical application of a probiotic ointment is feasible to achieve persistence of lactobacilli for at least 10 days.

Serine proteases represent an essential part of cellular homeostasis by generating biologically active peptides. In bacteria, proteolysis serves two different roles: a major housekeeping function and the destruction of foreign or target cell proteins, thereby promoting bacterial invasion. In the process, other virulence factors such as exotoxins become affected. In Staphylococcus aureus culture supernatant, the pore-forming alpha-toxin is cleaved by the coexpressed V8 protease and aureolysin. The oligomerizing and pore-forming abilities of five such spontaneously occurring N- and C-terminal alpha-toxin fragments were studied. (3)H-marked alpha-toxin fragments bound to rabbit erythrocyte membranes but only fragments with intact C termini, missing 8, 12 and 71 amino acids from their N-terminal, formed stable oligomers. All isolated fragments induced intoxication of mouse adrenocortical Y1 cells in vitro, though the nature of membrane damage for a fragment, degraded at its C terminus, remained obscure. Only one fragment, missing the first eight N-terminal amino acids, induced irreversible intoxication of Y1 cells in the same manner as the intact toxin. Four of the isolated fragments caused swelling, indicating altered channel formation. Fragments missing 12 and 71 amino acids from the N terminus occupied the same binding sites on Y1 cell membranes, though they inhibited membrane damage caused by intact toxin. In conclusion, N-terminal deletions up to 71 amino acids are tolerated, though the kinetics of channel formation and the channel's properties are altered. In contrast, digestion at the C terminus results in nonfunctional species.

Pore formation by four spontaneously occurring alpha-toxin fragments from Staphylococcus aureus were investigated on liposome and erythrocyte membranes. All the isolated fragments bound to the different types of membranes and formed transmembrane channels in egg-phosphatidyl glycerol vesicles. Fragments of amino acids (aa) 9-293 (32 kD) and aa 13-293 (31 kD) formed heptamers, similar to the intact toxin, while the aa 72-293 (26 kD) fragment formed heptamers, octamers, and nonamers, as judged by gel electrophoresis of the liposomes. All isolated fragments induced release of chloride ions from large unilamellar vesicles. Channel formation was promoted by acidic pH and negatively charged lipid head groups. Also, the fragments' hemolytic activity was strongly decreased under neutral conditions but could be partially restored by acidification of the medium. We paid special attention to the 26-kD fragment, which, despite the loss of about one-fourth of the N-terminal part of alpha-toxin, did form transmembrane channels in liposomes. In light of the available data on channel formation by alpha-toxin, our results suggest that proteolytic degradation might be better tolerated than previously reported. Channel opening could be inhibited and open channels could be closed by zinc in the medium. Channel closure could be reversed by addition of EDTA. In contrast, digestion at the C terminus led to premature oligomerization and resulted in species with strongly diminished activity and dependent on protonation.

Biosensoren, die die spezifischen Bindungseigenschaften von Enzymen, Antikörpern und Nukleinsäuren ausnutzen, sind in der Vergangenheit in großer Anzahl für die Detektion von Metaboliten, Hormonen und speziellen Nukleinsäuresequenzen beschrieben worden. Neuere Entwicklungen sind darauf gerichtet, neben biologischen auch biomimetische Erkennungselemente einzusetzen. Die Verwendung dieser Elemente könnte in Zukunft zu einer Erweiterung des detektierbaren Analytspektrums und zu höheren Funktionsstabilitäten der Sensoren führen. Dabei erscheinen Antikörper, Aptamere und molekular geprägte Polymere als besonders geeignet. In der vorliegenden Arbeit wird die Herstellung von Biomimetika in Form von Antikörpern und molekularen Imprints zur Creatininbindung und zur Phenylcarbamathydrolyse beschrieben und die Kombinationen mit elektrochemischen Sensoren aufgezeigt.