Project description:Aeromonas caviae has been associated with human gastrointestinal disease. Strains of this species typically lack virulence factors (VFs) such as enterotoxins and hemolysins that are produced by other human pathogens of the Aeromonas genus. Microarray profiling of murine small intestinal extracts, 24 hours after oral infection with an A. caviae strain, provides evidence of a Th1 type immune response. A large number of gamma-interferon (γ-IFN) induced genes are up-regulated as well as several tumor necrosis factor-alpha (TNF-α) transcripts. A. caviae has always been considered an opportunistic pathogen because it lacks obvious virulence factors. This current effort suggests A. caviae colonizes murine intestinal tract and causes what has been described by others as a dysregulatory cytokine response leading to an irritable bowel-like syndrome. This response would explain why a number of diarrheal waterborne outbreaks have been attributed to A. caviae even though it lacks obvious enteropathogenic properties. Keywords: Aeromonas caviae, infection, disease mechanism, TH1 resposne
Project description:Aeromonas are ubiquitous inhabitants of both natural and anthropogenic aquatic ecosystems. Occasionally, Aeromonas also grows in drinking water distribution systems, which is highly undesired due to the pathogenicity of some members of this genus. The growth of Aeromonas in such highly oligotrophic environments is currently poorly understood. Possible nutrient sources are biopolymers. For example, chitin is the structural component of the exoskeleton of insects, some invertebrates and the cell walls of fungi which makes it one of the most abundant carbon and nitrogen sources in nature. In this study we demonstrate the ability of two Aeromonas strains, Aeromonas bestiarum and Aeromonas rivuli to efficiently grow on chitin. The secreted proteins confirm the presence of the functional hydrolytic enzymes that enable the efficient degradation and utilization of this abundant biopolymer. Further quantitative cellular proteomic study unravels the remarkable reorganization of the Aeromonas metabolism when switching to chitin as sole carbon and nitrogen source. This proves that Aeromonas is not only chitinolytic but also a chitinotrophic microorganism.
Project description:Ulcerative colitis (UC) is an inflammatory bowel disease characterized by disruption of the epithelial barrier, and its etiology has long been enigmatic. We here observed a significant depletion of macrophages directly beneath the UC epithelial layer, and hypothesized that this depletion may be caused by a toxic bacteria. By screening fecal bacteria of UC patients, we identified the causative bacteria as Aeromonas spp MTB (macrophage-toxic bacteria), a novel variant of Aeromonas genus. The expressed aerolysin was preferentially toxic towards macrophages, and severs as a primary virulent factor. MTB efficiently colonized mice after pretreatment with DSS and antibiotics, and thereby induced UC-like colitis. Moreover, both aerolysin toxin and fecal MTB respectively distributed in UC colon tissue and stool with high frequency. We thus proposed that MTB infection was causally linked to ulcerative colitis. As aerolysin antibody mitigated the colitis phenotypes, our result also revealed an innovative therapeutic approach for UC.