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Query: UMLS:C0017160 (gastroenteritis)
 11,398 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The study of enterotoxins began in earnest approximately 30 years ago with characterization of the cholera toxin. So far, more enterotoxins have been associated with Gram-negative rather than Gram-positive bacteria. These substances can be roughly divided into the cytotonic variety, which primarily interfere with intestinal cell metabolism, and those which are cytotoxic, responsible for cell destruction. Most cytotonic enterotoxins activate cyclic adenosine monophosphate (cAMP) or cyclic guanosine monophosphate (cGMP) producing watery diarrhea, resulting from fluid and electrolyte flux. This typically results after binding to a toxin-specific receptor site on the small intestinal epithelium. Cytotoxic enterotoxins may interfere with protein synthesis in cells of the colonic epithelium and cause bloody, sometimes fatal dysentery. As more enterotoxins are discovered, it is becoming apparent that such variables as anatomic site and mode of action may not, in fact, be definitive criteria for classifying these substances. As a result, no universally acceptable classification scheme has yet been devised. Moreover, the biochemical and physiological characteristics of many enterotoxins and their role in gastroenteritis and other disorders remain speculative.
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PMID:Review of selected bacterial enterotoxins and their role in gastroenteritis. 328 66

We investigated global patterns of variation in 157 whole-genome sequences of Vibrio parahaemolyticus, a free-living and seafood associated marine bacterium. Pandemic clones, responsible for recent outbreaks of gastroenteritis in humans, have spread globally. However, there are oceanic gene pools, one located in the oceans surrounding Asia and another in the Mexican Gulf. Frequent recombination means that most isolates have acquired the genetic profile of their current location. We investigated the genetic structure in the Asian gene pool by calculating the effective population size in two different ways. Under standard neutral models, the two estimates should give similar answers but we found a 27-fold difference. We propose that this discrepancy is caused by the subdivision of the species into a hundred or more ecotypes which are maintained stably in the population. To investigate the genetic factors involved, we used 51 unrelated isolates to conduct a genome-wide scan for epistatically interacting loci. We found a single example of strong epistasis between distant genome regions. A majority of strains had a type VI secretion system associated with bacterial killing. The remaining strains had genes associated with biofilm formation and regulated by cyclic dimeric GMP signaling. All strains had one or other of the two systems and none of isolate had complete complements of both systems, although several strains had remnants. Further "top down" analysis of patterns of linkage disequilibrium within frequently recombining species will allow a detailed understanding of how selection acts to structure the pattern of variation within natural bacterial populations.
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PMID:Epidemic Clones, Oceanic Gene Pools, and Eco-LD in the Free Living Marine Pathogen Vibrio parahaemolyticus. 2560 90

Among human food-borne pathogens, gastroenteritis-causing Salmonella strains have the most real-world impact. Like all pathogens, their success relies on efficient transmission. Biofilm formation, a specialized physiology characterized by multicellular aggregation and persistence, is proposed to play an important role in the Salmonella transmission cycle. In this manuscript, we used luciferase reporters to examine the expression of csgD, which encodes the master biofilm regulator. We observed that the CsgD-regulated biofilm system responds differently to regulatory inputs once it is activated. Notably, the CsgD system became unresponsive to repression by Cpx and H-NS in high osmolarity conditions and less responsive to the addition of amino acids. Temperature-mediated regulation of csgD on agar was altered by intracellular levels of RpoS and cyclic-di-GMP. In contrast, the addition of glucose repressed CsgD biofilms seemingly independent of other signals. Understanding the fine-tuned regulation of csgD can help us to piece together how regulation occurs in natural environments, knowing that all Salmonella strains face strong selection pressures both within and outside their hosts. Ultimately, we can use this information to better control Salmonella and develop strategies to break the transmission cycle.
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PMID:Metabolic Activation of CsgD in the Regulation of Salmonella Biofilms. 3260 94