Dynamics of Clostridium difficile infection. Control using diet

Dietary therapy for clostridium difficile colonization: A case series

Clostridium difficile (C. difficile) is an important nosocomial pathogen in adults and children. Roughly 4-5% of non hospitalized healthy adults carry the organism in their intestinal flora while adults in long term care facilities have asymptomatic carriage rates estimated at 20-50%. C. difficile colonization results in a spectrum of clinical conditions from asymptomatic carrier state to fulminant colitis. Changes in the fecal microbiome are central in the development of C. difficile colonization and disease pathogenesis. C. difficile infection has been shown to be associated with reduced biodiversity of the gut microbiome and intestinal dysbiosis. With the importance of the intestinal microbiota in development of CDI and with the known impact of diet on the intestinal microbiota, we report the first known case of C. difficile colonization/recurrence successful treated by dietary modification.

Clostridium difficile toxin synthesis is negatively regulated by TcdC

Clostridium difficile toxin synthesis is growth phase-dependent and is regulated by various environmental signals. The toxin genes tcdA and tcdB are located in a pathogenicity locus, which also includes three accessory genes, tcdR, tcdC and tcdE. TcdR has been shown to act as an alternative σ factor that mediates positive regulation of both the toxin genes and its own gene. The tcdA, tcdB and tcdR genes are transcribed during the stationary growth phase. The tcdC gene, however, is expressed during exponential phase. This expression pattern suggested that TcdC may act as a negative regulator of toxin gene expression. TcdC is a small acidic protein without any conserved DNA-binding motif. It is able to form dimers and its N-terminal region includes a putative transmembrane domain. Genetic and biochemical evidence showed that TcdC negatively regulates C. difficile toxin synthesis by interfering with the ability of TcdR-containing RNA polymerase to recognize the tcdA and tcdB promoters. In addition, the C. difficile NAP1/027 epidemic strains that produce higher levels of toxins have mutations in tcdC. Interestingly, a frameshift mutation at position 117 of the tcdC coding sequence seems to be, at least in part, responsible for the hypertoxigenicity phenotype of these epidemic strains.

Correlation of disease severity with fecal toxin levels in patients with Clostridium difficile-associated diarrhea and distribution of PCR ribotypes and toxin yields in vitro of corresponding isolates

We investigated in vivo and in vitro yields of toxins A and B from and PCR ribotypes of Clostridium difficile isolates from 164 patients with differing severities of C. difficile-associated diarrhea (CDAD) (patients were grouped as follows: <3 loose stools per day, n = 45; 3 to 10 per day, n = 97; >10 per day, n = 22). The median fecal toxin levels in each group were 0.5, 6.8, and 149 U/g feces (P < 0.001), respectively. Patients with severe diarrhea also had more-frequent occurrence of blood in stool and vomiting, but there was no association with fecal toxin levels per se. There was no correlation between fecal toxin level and toxin yield in vitro for the corresponding C. difficile isolate or between its PCR ribotype and disease severity. A broad range of toxin yields among isolates belonging to major PCR ribotypes indicated a presence of many subtypes. We hypothesize that bacterial and host factors that affect C. difficile toxin levels in feces are important determinants of symptoms in CDAD patients. An inverse correlation between toxin yield and spore count (r = 0.66) in stationary-phase cultures supported the notion that toxin production and sporulation represent opposite alternative survival strategies for C. difficile cells facing nutrient shortage.