Salmonella enterica represents a major human and animal pathogen. Many S. enterica genomes have been completed and many more genome sequencing projects are underway, constituting an excellent resource for comparative genome analysis studies leading to a better understanding of bacterial evolution and pathogenesis. Salmonella enterica serovar Typhimurium and Typhi are the best-characterized serovars, with the first being involved in localized gastroenteritis in many hosts and the latter causing a systemic human-specific disease. Here, we summarize the major genetic differences between the two different serovars. We detail the divergent repertoires of the virulence factors responsible for the pathogenesis of the organisms and that ultimately result in the distinct clinical outcomes of infection. This comparative genomic overview highlights hypotheses for future investigations on S. enterica pathogenesis and the basis of host specificity.

SummaryConsecutive patients undergoing knee arthroplasty or tibial osteotomy at four participating hospitals received either enoxaparin, 30 mg subcutaneously every 12 h (n = 66) or an identicalappearing placebo (n = 65). All study medications started the morning after the operation and were continued up to a maximum of 14 days. Patients underwent surveillance with 125I-fibrinogen leg scanning and impedance plethysmography. Bilateral contrast venography was performed routinely at Day 14 or at time of discharge, if sooner. Deep vein thrombosis was detected by venography in 35 of 54 patients (65%) in the placebo group and in 8 of 41 patients in the enoxaparin group (19%), a risk reduction of 71%, P <0.0001. For the entire study group, deep vein thrombosis was detected by either venography of non-invasive tests in 37 of 64 patients (58%) in the placebo group and in 11 of 65 patients (17%) in the enoxaparin group, a risk reduction of 71%, P <0.0001. Proximal vein thrombosis was found in 19% of the placebo patients and in none of the enoxaparin patients, a risk reduction of 100%, P <0.001. Bleeding complications occurred in 5 of 65 patients (8%) in the placebo group and in 4 of 66 patients (6%) in the enoxaparin group, P = 0.71. There were no differences in the amount of blood loss, minimum hemoglobin levels and number of units of packed red cells given between the two treatment groups. We conclude that a fixed dose regimen of enoxaparin, started post-operatively, is an effective and safe regimen for reducing the frequency of deep vein thrombosis after major knee surgery.

No abstract

dCitrobacter rodentium is a murine intestinal pathogen used as a model for the foodborne human pathogens enterohemorrhagic Escherichia coli and enteropathogenic E. coli. During infection, these pathogens use two-component signal transduction systems to detect and adapt to changing environmental conditions. In E. coli, the CpxRA two-component signal transduction system responds to envelope stress by modulating the expression of a myriad of genes. Quantitative real-time PCR showed that cpxRA was expressed in the colon of C57BL/6J mice infected with C. rodentium. To determine whether CpxRA plays a role during C. rodentium infection, a cpxRA deletion strain was generated and found to have a colonization defect during infection. This defect was independent of an altered growth rate or a defective type III secretion system, and single-copy chromosomal complementation of cpxRA restored virulence. The C. rodentium strains were then tested in C3H/HeJ mice, a lethal intestinal infection model. Mice infected with the ⌬cpxRA strain survived infection, whereas mice infected with the wild-type or complemented strains succumbed to infection. Furthermore, we found that the cpxRA expression level was higher during early infection than at a later time point. Taken together, these data demonstrate that the CpxRA two-component signal transduction system is essential for the in vivo virulence of C. rodentium. In addition, these data suggest that fine-tuned cpxRA expression is important for infection. This is the first study that identifies a C. rodentium two-component transduction system required for pathogenesis. This study further indicates that CpxRA is an interesting target for therapeutics against enteric pathogens.