Adaptive Strategies and Pathogenesis of Clostridium difficile fromIn VivoTranscriptomics

Abstract

f Clostridium difficile is currently the major cause of nosocomial intestinal diseases associated with antibiotic therapy in adults. In order to improve our knowledge of C. difficile-host interactions, we analyzed the genome-wide temporal expression of C. difficile 630 genes during the first 38 h of mouse colonization to identify genes whose expression is modulated in vivo, suggesting that they may play a role in facilitating the colonization process. In the ceca of the C. difficile-monoassociated mice, 549 genes of the C. difficile genome were differentially expressed compared to their expression during in vitro growth, and they were distributed in several functional categories. Overall, our results emphasize the roles of genes involved in host adaptation. Colonization results in a metabolic shift, with genes responsible for the fermentation as well as several other metabolic pathways being regulated inversely to those involved in carbon metabolism. In addition, several genes involved in stress responses, such as ferrous iron uptake or the response to oxidative stress, were regulated in vivo. Interestingly, many genes encoding conserved hypothetical proteins (CHP) were highly and specifically upregulated in vivo. Moreover, genes for all stages of sporulation were quickly induced in vivo, highlighting the observation that sporulation is central to the persistence of C. difficile in the gut and to its ability to spread in the environment. Finally, we inactivated two genes that were differentially expressed in vivo and evaluated the relative colonization fitness of the wild-type and mutant strains in coinfection experiments. We identified a CHP as a putative colonization factor, supporting the suggestion that the in vivo transcriptomic approach can unravel new C. difficile virulence genes.

The Phosphotransfer Protein CD1492 Represses Sporulation Initiation in Clostridium difficile

“…A few negative regulators of SigD have been identified, including the early sporulation effector RstA, the stationary-phase sigma factor SigH, and (24,39,48,49). We examined the transcription of rstA on sporulation medium and found that its expression was more than 3-fold lower in the CD1492 mutant than in the parent strain (Fig.…”

CodY-Dependent Regulation of Sporulation in Clostridium difficile

“…Lower nutrient uptake would cause derepression of CodY-and CcpA-responsive genes and increased SigD activity, all of which would result in higher toxin expression (53,56,63,72). A comparison of gene expression levels for C. difficile grown in vitro and in vivo found a substantially greater impact on metabolism and sporulation under in vivo conditions than under in vitro conditions (82). This discrepancy highlights the need for greater understanding of the nutritional environment present during C. difficile infections, which could be used to improve conditions for examining these physiological processes in vitro.…”

Characterization of the Dynamic Germination of Individual Clostridium difficile Spores Using Raman Spectroscopy and Differential Interference Contrast Microscopy

“…Once established in the gastrointestinal tract, C. difficile secretes two toxins, the enterotoxin TcdA and the cytotoxin TcdB, that cause massive damage to the intestinal epithelium and induce strong inflammatory responses (6). During growth in the gastrointestinal tract, C. difficile strongly induces a transcriptional program that leads to spore formation (7). Spore formation is essential for C. difficile to survive exit from the host and transmit disease because its vegetative cells are exquisitely sensitive to oxygen (8).…”