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Streptococcus suis is an important swine pathogen that causes meningitis, endocarditis, arthritis and septicaemia. As a zoonotic agent, S. suis also causes similar diseases in humans. Binding of pathogenic bacteria to extracellular matrix components enhances their adhesion to and invasion of host cells. In the present study we isolated and identified a novel fibronectin-binding protein from S. suis. The native protein (designated SsEno) possessed not only high homology with other bacterial enolases but also enolase activity. We cloned, expressed and purified SsEno and showed that it is ubiquitously expressed by all S. suis serotypes and we identified its surface localization using immunoelectron microscopy. ELISA demonstrated that SsEno binds specifically to fibronectin and plasminogen in a lysine-dependent manner. Additional surface plasmon resonance assays demonstrated that SsEno binds to fibronectin or plasminogen with low nanomolar affinity. Inhibition experiments with anti-SsEno antibodies also showed that bacterial SsEno is important for the adhesion to and invasion of brain microvascular endothelial cells by S. suis. Overall, the present work is the first study, to our knowledge, to demonstrate a fibronectin-binding activity of a bacterial enolase, and shows that, similar to other bacterial fibronectin-binding proteins, SsEno may contribute to the virulence of S. suis.

Environmental phosphate is an important signal for microorganism gene regulation, and it has recently been shown to trigger some key bacterial virulence mechanisms. In many bacteria, the Pho regulon is the major circuit involved in adaptation to phosphate limitation. The Pho regulon is controlled jointly by the two-component regulatory system PhoR/PhoB and by the phosphate-specific transport (Pst) system, which both belong to the Pho regulon. We showed that a pst mutation results in virulence attenuation in extraintestinal pathogenic Escherichia coli (ExPEC) strains. Our results indicate that the bacterial cell surface of the pst mutants is altered. In this study, we show that pst mutants of ExPEC strains display an increased sensitivity to different cationic antimicrobial peptides and vancomycin. Remarkably, the hexa-acylated 1-pyrophosphate form of lipid A is significantly less abundant in pst mutants. Among differentially expressed genes in the pst mutant, 1pxT coding for an enzyme that transfers a phosphoryl group to lipid A, forming the 1-diphosphate species, was found to be downregulated. Our results strongly suggest that the Pho regulon is involved in lipid A modifications, which could contribute to bacterial surface perturbations. Since the Pho regulon and the Pst system are conserved in many bacteria, such a lipid A modification mechanism could be widely distributed among gram-negative bacterial species.

Research has been conducted on the amino acid polypeptide of the heat-stable Escherichia coli enterotoxin b. The role of the selected amino acids in the enterotoxicity and the involvement of these amino acids in the interactions of enterotoxin b with the functional receptor sulfatide have been investigated.

Escherichia coli STb enterotoxin has been linked to diarrhoea illnesses of porcine origin. However, STb gene was alo found to be present in bovine, chicken and even human enterotoxigenic E. coli (ETEC) strains. STb has been documented as having effects on intestinal tissue through two possible mechanisms. It mediates the level of prostaglandin E2 which regulates water and electrolyte in diarhoea. The second mechanism involves the receptor-operative calcium channel in the plasma membrane.

Affinity chromatography of the haemolysin toxin from Streptococcus suis type 2 using a thiopropyl Sepharose 6B column reveals that the extracellular protein has a molecular mass of 65 kDa. The haemolysin's response to oxygen and oxidizing agents, suppression by low levels of cholesterol, stimulation by reducing agents and transmembrane pore formation enable its classification into a family of antigenically related cholesterol-binding cytolytic toxins. S. suis haemolysin haemolytic activity is prevented by anti-streptolysin antibodies.

The enterotoxigenic Escherichia coli estB gene codes for the heat-stable entrotoxin b (STb) associated with swine diarrhea. To overexpress STb, the estB gene was fused to the malB gene coding for a maltose-binding protein and the construct was placed under the control of a strong promoter. Expression of the hybrid plasmid resulted in the synthesis of the fusion protein in the periplasm of E. coli. The STb portion of the fusion protein could be recovered by cleavage with Xa protease.

Thenauthors review the publications on Helicobacter pylori. The topics of interest include the interactions with host serum and interplay of H. pylori virulence factors resulting in cell damage.

Enterotoxigenic Escherichia coli (ETEC) produces two types of enterotoxins: heat-labile (LT) and heat-stable (STa and STb). These molecules are involved in the induction of secretory diarrhea in animals including humans. This condition is currently treated using a fluid replacement therapy and antibiotics. This treatment is often not available to people in developing countries, and several die from the condition provoke by ETEC. Over the years, plants and plant extracts have been use as traditional medicine to treat various gastrointestinal ailments including diarrhea. Many of these plant products have been claimed to be active against diarrhea, however few have been extensively studied. The main objective of this review was to gather the scattered information on the antidiarrheal activities reported for various plant products on ETEC. This includes two major effects: (1) The inhibitory effect on bacterial growth or viability and (2) The interference with ETEC enterotoxins activity upon the intestinal epithelium. We will focus on plant products and extracts for which we have major indications of their biological activity against ETEC and their enterotoxins. Because Vibrio cholerae toxin (CT) is structurally, antigenically and mechanistically related to LT, it will also be discussed in this review. [ABSTRACT FROM AUTHOR]