Identification of an Escherichia coli operon required for formation of the O-antigen capsule

Escherichia coli produces polysaccharide capsules that, based on their mechanisms of synthesis and assembly, have been classified into four groups. The group 4 capsule (G4C) polysaccharide is frequently identical to that of the cognate lipopolysaccharide O side chain and has, therefore, also been termed the O-antigen capsule. The genes involved in the assembly of the group 1, 2, and 3 capsules have been described, but those required for G4C assembly remained obscure. We found that enteropathogenic E. coli (EPEC) produces G4C, and we identified an operon containing seven genes, ymcD, ymcC, ymcB, ymcA, yccZ, etp, and etk, which are required for formation of the capsule. The encoded proteins appear to constitute a polysaccharide secretion system. The G4C operon is absent from the genomes of enteroaggregative E. coli and uropathogenic E. coli. E. coli K-12 contains the G4C operon but does not express it, because of the presence of IS1 at its promoter region. In contrast, EPEC, enterohemorrhagic E. coli, and Shigella species possess an intact G4C operon.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/92199/1/174504.pd

CCL24 regulates biliary inflammation and fibrosis in primary sclerosing cholangitis

ˆCCL24 is a pro-fibrotic, pro-inflammatory chemokine expressed in several chronic fibrotic diseases. In the liver, CCL24 plays a role in fibrosis and inflammation, and blocking CCL24 led to reduced liver injury in experimental models. We studied the role of CCL24 in primary sclerosing cholangitis (PSC) and evaluated the potential therapeutic effect of blocking CCL24 in this disease. Multidrug resistance gene 2-knockout (Mdr2-/-) mice demonstrated CCL24 expression in liver macrophages and were used as a relevant experimental PSC model. CCL24-neutralizing monoclonal antibody, CM-101, significantly improved inflammation, fibrosis, and cholestasis-related markers in the biliary area. Moreover, using spatial transcriptomics, we observed reduced proliferation and senescence of cholangiocytes following CCL24 neutralization. Next, we demonstrated that CCL24 expression was elevated under pro-fibrotic conditions in primary human cholangiocytes and macrophages, and it induced proliferation of primary human hepatic stellate cells and cholangiocytes, which was attenuated following CCL24 inhibition. Correspondingly, CCL24 was found to be highly expressed in liver biopsies of patients with PSC. CCL24 serum levels correlated with Enhanced Liver Fibrosis score, most notably in patients with high alkaline phosphatase levels. These results suggest that blocking CCL24 may have a therapeutic effect in patients with PSC by reducing liver inflammation, fibrosis, and cholestasis

Temporal Trends of Transcatheter Aortic Valve Implantation over 12 Years: A High-Volume Single-Center Experience

Transcatheter aortic valve replacement (TAVR) has become the mainstay of treatment for patients with severe AS. Since the TAVR population and patients’ outcomes have dramatically changed over the last decade, updated data regarding contemporary practice and trends are pertinent to clinical use. We performed a retrospective observational analysis of consecutive patient who underwent TAVR for symptomatic severe AS between the years 2009 and 2021 in a single high-volume center. Patients were divided into four equal time groups based on the procedure date (2009–2012, 2013–2015, 2016–2018 and 2019–2021). A total of 1988 patients were included in this study and divided into four groups, with 321, 482, 565 and 620 patients in groups 1–4, respectively. Significant trends were seen in baseline characteristics of a few parameters, including lower age, lower procedural risk and reduced rates of comorbidity (p for trend < 0.0001 for all factors mentioned above). A shift was seen in the procedural technique with lower balloon pre-dilatation and higher device success rates (p for trend < 0.0001). The post-procedural period changed over the years with fewer pacemaker placements (p < 0.0001) and reduced rates of AKI and post-procedural bleed (p value 0.02 and <0.0001, respectively). Furthermore, overall hospital stay was shortened from 7 ± 7.1 days to 2.3 ± 1.7 (p < 0.0001). Finally, patient follow up revealed reduced mortality rates at 30 days (p < 0.0001) and 1 year (p = 0.013). Multivariate regression revealed that a late implantation date was an independent protector from mortality (HR 0.84, p = 0.002). In conclusion, our study demonstrated that TAVR has become a safer practice over the years with reduced rates of morbidity and mortality

Transient Shielding of Intimin and the Type III Secretion System of Enterohemorrhagic and Enteropathogenic Escherichia coli by a Group 4 Capsule▿ †

Enterohemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC, respectively) strains represent a major global health problem. Their virulence is mediated by the concerted activity of an array of virulence factors including toxins, a type III protein secretion system (TTSS), pili, and others. We previously showed that EPEC O127 forms a group 4 capsule (G4C), and in this report we show that EHEC O157 also produces a G4C, whose assembly is dependent on the etp, etk, and wzy genes. We further show that at early time points postinfection, these G4Cs appear to mask surface structures including intimin and the TTSS. This masking inhibited the attachment of EPEC and EHEC to tissue-cultured epithelial cells, diminished their capacity to induce the formation of actin pedestals, and attenuated TTSS-mediated protein translocation into host cells. Importantly, we found that Ler, a positive regulator of intimin and TTSS genes, represses the expression of the capsule-related genes, including etp and etk. Thus, the expression of TTSS and G4C is conversely regulated and capsule production is diminished upon TTSS expression. Indeed, at later time points postinfection, the diminishing capsule no longer interferes with the activities of intimin and the TTSS. Notably, by using the rabbit infant model, we found that the EHEC G4C is required for efficient colonization of the rabbit large intestine. Taken together, our results suggest that temporal expression of the capsule, which is coordinated with that of the TTSS, is required for optimal EHEC colonization of the host intestine