Competitive exclusion of Salmonella enteritidis by Salmonella gallinarum in poultry.

Salmonella Enteritidis emerged as a major egg-associated pathogen in the late 20th century. Epidemiologic data from England, Wales, and the United States indicate that S. Enteritidis filled the ecologic niche vacated by eradication of S. Gallinarum from poultry, leading to an epidemic increase in human infections. We tested this hypothesis by retrospective analysis of epidemiologic surveys in Germany and demonstrated that the number of human S. Enteritidis cases is inversely related to the prevalence of S. Gallinarum in poultry. Mathematical models combining epidemiology with population biology suggest that S. Gallinarum competitively excluded S. Enteritidis from poultry flocks early in the 20th century

Gut inflammation provides a respiratory electron acceptor for Salmonella.

Salmonella enterica serotype Typhimurium (S. Typhimurium) causes acute gut inflammation by using its virulence factors to invade the intestinal epithelium and survive in mucosal macrophages. The inflammatory response enhances the transmission success of S. Typhimurium by promoting its outgrowth in the gut lumen through unknown mechanisms. Here we show that reactive oxygen species generated during inflammation react with endogenous, luminal sulphur compounds (thiosulphate) to form a new respiratory electron acceptor, tetrathionate. The genes conferring the ability to use tetrathionate as an electron acceptor produce a growth advantage for S. Typhimurium over the competing microbiota in the lumen of the inflamed gut. We conclude that S. Typhimurium virulence factors induce host-driven production of a new electron acceptor that allows the pathogen to use respiration to compete with fermenting gut microbes. Thus the ability to trigger intestinal inflammation is crucial for the biology of this diarrhoeal pathogen

Acupuncture Point Localization Varies Among Acupuncturists

Background: Studies assessing the point-specific effect of acupuncture or the characteristics of acupuncture points (APs) tend to yield inconclusive results. In order to identify a possible confounding factor, we aimed to examine the variability in AP localization by means of a survey. Material and Methods: Attendees of the 14th ICMART (International Council of Medical Acupuncture and Related Techniques) congress as well as DAGfA (German Medical Society of Acupuncture) lecturers and students were asked to locate and mark the APs LI 10 and TH 5 on a research assistant's arm. Identified points were transferred into a coordinate system, and the respective bivariate distribution function was calculated. Additionally, participants filled out a questionnaire about their acupuncture education and experience, the acupuncture style and point localization techniques used most frequently, and their estimation of the size of an AP. Results: The areas of the ellipses, theoretically containing 95% of AP localizations, varied between 44.49 and 5.18 cm(2). The largest distance between 2 identified points was 8.45 cm for LI 10 and 5.3 cm for TH 5. Apart from being trained at the same school, no other factor could be identified that determined the variability in AP localization. Conclusion: Our results indicate that congruity of AP localization among experienced acupuncturists might be low. Although there are some limitations to our results, this possible bias should be taken into account when conducting acupuncture trials and interpreting results of previous acupuncture studies

Nagetier-übertragene Zoonosen: Beispiele aus Untersuchungen in Süd- und Westdeutschland

Zusammenfassung Nagetiere und andere Kleinsäuger können eine Vielzahl von Krankheitserregern, RNA- und DNA-Viren, Bakterien und Parasiten, auf den Menschen übertragen, die teilweise lebensbedrohliche Erkrankungen hervorrufen. In der folgenden Übersicht soll erstmals ein Überblick über Ergebnisse aus drei Untersuchungen in Deutschland gegeben werden: eine Studie in drei Landkreisen Bayerns von 2001-2004, Untersuchungen in einem Freilandgehege im Rahmen eines Tularämieausbruchs in Niedersachsen im Jahr 2005, und schließlich im Jahr 2007 eine Untersuchung an einem Truppenübungsplatz in Baden-Württemberg. Es wurde dabei exemplarisch die Verbreitung von Zoonoseerregern in Nagetieren und anderen Kleinsäugern näher untersucht, von drei Viren (Hantaviren, Kuhpockenvirus, Frühsommer- Meningo-Enzephalitis-Virus) und vier Bakterien (Leptospiren, Francisellen, Borrelien und Rickettsien). Die hier zusammengefassten Erkenntnisse sind ein erster wichtiger Schritt auf dem Weg zur Erstellung von Verbreitungskarten für die genannten humanpathogenen Zoonoseerreger in ihren Reservoirwirten und der Definition von entsprechenden Risikogebieten. Diese Arbeit soll zudem einen Beitrag leisten, einen Anstoß zu verstärkter Zusammenarbeit von Zoologen, Ökologen, Virologen, Human- und Veterinärmedizinern, Mikrobiologen, Parasitologen, Genetikern, Epidemiologen, Forstwissenschaftlern und Klimaforschern zu geben

A Complete Axiom System for Propositional Interval Temporal Logic with Infinite Time

Interval Temporal Logic (ITL) is an established temporal formalism for reasoning about time periods. For over 25 years, it has been applied in a number of ways and several ITL variants, axiom systems and tools have been investigated. We solve the longstanding open problem of finding a complete axiom system for basic quantifier-free propositional ITL (PITL) with infinite time for analysing nonterminating computational systems. Our completeness proof uses a reduction to completeness for PITL with finite time and conventional propositional linear-time temporal logic. Unlike completeness proofs of equally expressive logics with nonelementary computational complexity, our semantic approach does not use tableaux, subformula closures or explicit deductions involving encodings of omega automata and nontrivial techniques for complementing them. We believe that our result also provides evidence of the naturalness of interval-based reasoning

Molecular and Phenotypic Analysis of the CS54 Island of Salmonella enterica Serotype Typhimurium: Identification of Intestinal Colonization and Persistence Determinants

The shdA gene is carried on a 25-kb genetic island at centisome 54 (CS54 island) of the Salmonella enterica serotype Typhimurium chromosome. In addition to shdA, the CS54 island of Salmonella serotype Typhimurium strain LT2 contains four open reading frames designated ratA, ratB, sivI, and sivH. DNA hybridization analysis revealed that the CS54 island is comprised of two regions with distinct phylogenetic distribution within the genus Salmonella. Homologues of shdA and ratB were detected only in serotypes of Salmonella enterica subsp. I. In contrast, sequences hybridizing with ratA, sivI, and sivH were present in S. enterica subsp. II and S. bongori in addition to S. enterica subsp. I. Deletion of the ratA and sivI genes did not alter the ability of Salmonella serotype Typhimurium to colonize the organs of mice. Insertional inactivation of the sivH gene resulted in defective colonization of the Peyer's patches of the terminal ileum but normal colonization of the cecum, mesenteric lymph nodes, and spleen. Deletion of the shdA gene resulted in decreased colonization of the cecum and Peyer's patches of the terminal ileum and colonization to a lesser degree in the mesenteric lymph nodes and spleen 5 days post-oral inoculation of mice. A strain containing a deletion in the ratB gene exhibited a defect for the colonization of the cecum but not of the Peyer's patches, mesenteric lymph nodes, and spleen. The shdA and ratB deletion strains exhibited a shedding defect in mice, whereas the sivH deletion strain was shed at numbers similar to the wild type. These data suggest that colonization of the murine cecum is required for efficient fecal shedding in mice

The Lack of Natural IgM Increases Susceptibility and Impairs Anti-Vi Polysaccharide IgG Responses in a Mouse Model of Typhoid

Circulating IgM present in the body prior to any apparent Ag exposure is referred to as natural IgM. Natural IgM provides protective immunity against a variety of pathogens. Salmonella enterica serovar Typhi (S. Typhi) is the causative agent of typhoid fever in humans. Because mice are not permissive to S. Typhi infection, we employed a murine model of typhoid using S. enterica serovar Typhimurium expressing the Vi polysaccharide (ViPS) of S. Typhi (S. Typhimurium strain RC60) to evaluate the role of natural IgM in pathogenesis. We found that natural mouse IgM binds to S. Typhi and S. Typhimurium. The severity of S. Typhimurium infection in mice is dependent on presence of the natural resistance-associated macrophage protein 1 (Nramp1) allele; therefore, we infected mice deficient in secreted form of IgM (sIgM) on either a Nramp1-resistant (129S) or -susceptible (C57BL/6J) background. We found that the lack of natural IgM results in a significantly increased susceptibility and an exaggerated liver pathology regardless of the route of infection or the Nramp1 allele. Reconstitution of sIgM-/- mice with normal mouse serum or purified polyclonal IgM restored the resistance to that of sIgM+/+ mice. Furthermore, immunization of sIgM-/- mice with heat-killed S. Typhi induced a significantly reduced anti-ViPS IgG and complement-dependent bactericidal activity against S. Typhi in vitro, compared with that of sIgM+/+ mice. These findings indicate that natural IgM is an important factor in reducing the typhoid severity and inducing an optimal anti-ViPS IgG response to vaccination

Divergent Roles of Salmonella Pathogenicity Island 2 and Metabolic Traits during Interaction of S. enterica Serovar Typhimurium with Host Cells

The molecular mechanisms of virulence of the gastrointestinal pathogen Salmonella enterica are commonly studied using cell culture models of infection. In this work, we performed a direct comparison of the interaction of S. enterica serovar Typhimurium (S. Typhimurium) with the non-polarized epithelial cell line HeLa, the polarized cell lines CaCo2, T84 and MDCK, and macrophage-like RAW264.7 cells. The ability of S. Typhimurium wild-type and previously characterized auxotrophic mutant strains to enter host cells, survive and proliferate within mammalian cells and deploy the Salmonella Pathogenicity Island 2-encoded type III secretion system (SPI2-T3SS) was quantified. We found that the entry of S. Typhimurium into polarized cells was much more efficient than entry into non-polarized cells or phagocytic uptake. While SPI2-T3SS dependent intracellular proliferation was observed in HeLa and RAW cells, the intracellular replication in polarized cells was highly restricted and not affected by defective SPI2-T3SS. The contribution of aromatic amino acid metabolism and purine biosynthesis to intracellular proliferation was distinct in the various cell lines investigated. These observations indicate that the virulence phenotypes of S. Typhimurium are significantly affected by the cell culture model applied