Evaluation of intestinal colonization of mice by <i>C. difficile</i>.

<p>Colonization was evaluated at days 1, 4, 8, 10 and 14 in the GroEL- immunized group and in the control group after intra-gastric administration of <i>C.difficile</i> to mice.</p

Kaplan-Meier survival estimates demonstrating time between challenge with <i>Clostridium difficile</i> and death.

<p>Clindamycin (50 mg/Kg) was administered 5 days before spore challenge. Animals were observed for 11 days. Experiments were performed with hamsters receiving PBS as control (n = 16) and hamsters immunized intra-rectally with cell wall extracts (CWE) (n = 20). Cholera toxin was used as adjuvant, for the two groups.</p

Course of colonization and death of hamsters challenged with <i>Clostridium difficile</i> after pre-treatment with clindamycin.

<p>Each circle represents the same animal on different days (D) of observation. White circles: uncolonized hamsters; grey circles: colonized hamsters, black circles: colonized hamsters that died.</p

2-DE map on 18 cm IPG strip of cell wall proteins extracts used for hamsters immunization.

<p>Spots circled correspond to immuno-reactive proteins, DnaK (1), GroEL (2), S-layer protein precursor (3).</p

Immunoblots of cell wall extracts revealed by sera of hamster from the control group (A) and cell wall extracts revealed by sera of hamster from the cell wall extracts immunized group (B).

<p>Spots circled correspond to immuno-reactive proteins, DnaK (1), GroEL (2), S-layer protein precursor (3).</p

Protein identification by MS and MS/MS analysis.

<p>Protein identification by MS and MS/MS analysis.</p

Validation of microarray data by qRT-PCR.

<p>Fold changes in in vivo gene expression at 4, 6, 14 and 38h post-infection, compared to the in vivo expression at 8h post-infection, were measured by microarray and qRT-PCR. Data are plotted as log₂ ratios of microarrays data (<i>x</i>-axis) compared with those of qRT-PCR (<i>y</i>-axis).</p

Regulation of toxin genes during the kinetics of infection.

<p>Regulation of toxin genes during the kinetics of infection.</p

Kinetics of sporulation rate in <i>C</i>. <i>difficile</i> associated mice.

<p>Mice were orally challenged with 1x10⁸ CFUs of vegetative cells. Vegetative cells were enumerated on BHI agar plates and spores after a heat shock treatment on BHI containing 0.1% of taurocholate sodium salt. </p

Deciphering Adaptation Strategies of the Epidemic <i>Clostridium difficile</i> 027 Strain during Infection through <i>In Vivo</i> Transcriptional Analysis

<div><p><i>Clostridium difficile</i> is responsible for a wide spectrum of infection from asymptomatic carriage to severe, relapsing colitis. Since 2003, <i>C</i>. <i>difficile</i> infections have increased with a higher morbidity and mortality due to the emergence of epidemic and hypervirulent <i>C</i>. <i>difficile</i> strains such as those of the epidemic lineage 027/BI/NAP1. To decipher the hypervirulence and epidemicity of 027 strains, we analyzed gene expression profiles of the R20291 027 strain using a monoxenic mouse model during the first 38h of infection. A total of 741 genes were differentially expressed during the course of infection. They are mainly distributed in functional categories involved in host adaptation. Several genes of PTS and ABC transporters were significantly regulated during the infection, underlying the ability of strain R20291 to adapt its metabolism according to nutrient availability in the digestive tract. In this animal model, despite the early sporulation process, sporulation efficiency seems to indicate that growth of R20291 vegetative cells versus spores were favored during infection. The bacterial mechanisms associated to adaptability and flexibility within the gut environment, in addition to the virulence factor expression and antibiotic resistance, should contribute to the epidemicity and hypervirulence of the <i>C</i>. <i>difficile</i> 027 strains.</p></div