Clostridium difficile special issue August 2011.

1 University of Edinburgh
Journal of Medical Microbiology (Impact Factor: 2.25). 06/2011; DOI: 10.1099/jmm.0.033985-0
Source: PubMed

ABSTRACT No abstract.

6 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: Clostridium difficile has emerged as a pathogen or commensal in food animals. There is overlap between isolates from animals, retail meats and humans, suggesting that animals may be a C. difficile reservoir. For direct detection of variant C. difficile strains in faecal samples of symptomatic and asymptomatic animals, we developed and validated a new TaqMan real-time PCR (TMrtPCR) assay targeting the tcdA, tcdB and cdtB genes. We compared it with the enrichment culture method and with two real-time PCR (rtPCR) assays, BrtPCR and PCRFast, targeting tcdB and tcdA/tcdB, respectively. All ten tested C. difficile toxinotypes, except one (XIa) with PCRFast and two (X, XIa) with BrtPCR, were detected with the test assays. A total of 340 (100 %) samples were cultured and amplified with TMrtPCR. Results correlated in 75.3 % samples. Forty (11.8 %) samples were culture positive/TMrtPCR negative, possibly because of the low numbers of bacteria in the samples or because of DNA extraction failure. Forty (11.8 %) samples were TMrtPCR positive/culture negative. Among 79 samples included in the rtPCR assays/culture comparison, 50.6 % were in complete concordance. The results showed that TMrtPCR performed better than BrtPCR and PCRFast, and 67 % of the culture-positive samples were TMrtPCR positive in comparison to 40 % of the samples positive in BrtPCR and 7 % of the samples positive in PCRFast, respectively. Another advantage of TMrtPCR over BrtPCR and PCRFast is its ability to detect a binary toxin gene. Therefore, the TMrtPCR results can provide the first information about the toxin type present in the sample. According to the results of our study, TMrtPCR could be a preferred screening method for the rapid detection of C. difficile in animal faecal samples, although an enrichment culture has to be performed for the specimens with negative or inconclusive rtPCR results.
    Journal of Medical Microbiology 04/2011; 60(Pt 8):1119-25. DOI:10.1099/jmm.0.030304-0 · 2.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The kinetics of bacterial killing for fidaxomicin and its major metabolite, OP-1118, were investigated against Clostridium difficile strains, including two clinical strains belonging to the restriction endonuclease analysis group BI (ORG 1687 and 1698), the ATCC 43255 strain and two laboratory-derived mutant strains with decreased susceptibility to fidaxomicin (ORG 919 and 1620). Both fidaxomicin and OP-1118 demonstrated time-dependent killing of C. difficile strains. Fidaxomicin (at 4× MIC) reduced bacterial counts of the ATCC 43255 strain, clinical strain ORG 1687 and the two laboratory-generated mutant strains by ≥3 logs within 48 h of exposure. The other BI strain, ORG 1698, was tested at 2× MIC fidaxomicin with bacterial counts decreasing 1 log in 48 h. Exposure to OP-1118 (at 4× MIC) also resulted in a ≥3 log drop in c.f.u. counts for the ATCC 43255 strain, the clinical BI strain ORG 1687 and the mutant strain ORG 919. Higher concentrations of OP-1118 (32× MIC) were required for a 3 log reduction in c.f.u. counts for the other BI strain, ORG 1698. In summary, the results indicate that both fidaxomicin and its major metabolite, OP-1118, are bactericidal against C. difficile strains, including the hypervirulent restriction endonuclease analysis group BI strains, at concentrations that are many fold below the detected faecal concentrations of these compounds after oral administration of fidaxomicin.
    Journal of Medical Microbiology 02/2011; 60(Pt 8):1213-7. DOI:10.1099/jmm.0.029470-0 · 2.25 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Clostridium difficile is a frequent cause of severe, recurrent, post-antibiotic diarrhoea and pseudomembranous colitis. Its pathogenicity is mediated mainly by two toxins, TcdA and TcdB. However, different adhesins have also been described as important colonization factors which are implicated in the first step of the intestinal infection. In this study, we focused our interest on one of these adhesins, fibronectin-binding protein A (FbpA), and on its role in the intestinal colonization process. A mutant of FbpA (CDΔFbpA) was constructed in C. difficile strain 630Δerm by using ClosTron technology. This mutant was characterized in vitro and in vivo and compared to the isogenic wild-type strain. Adhesion of the CDΔFbpA mutant to the human colonic epithelial cell line Caco-2 and to mucus-secreting HT29-MTX cells was examined. Surprisingly, the CDΔFbpA mutant adhered more than the wild-type parental strain. The CDΔFbpA mutant was also analysed in three different mouse models by following the intestinal implantation kinetics (faecal shedding) and caecal colonization (7 days post-challenge). We showed that in monoxenic mice, CDΔFbpA shed C. difficile in faeces at the same rate as that of the isogenic wild-type strain but its colonization of the caecal wall was significantly reduced. In dixenic mice, the shedding rate was slower for the CDΔFbpA mutant than for the isogenic wild-type strain during the first days of infection, but no significant difference was observed in caecal colonization. Similar rates of intestinal implantation and caecal colonization were observed for both strains in assays performed in human microbiota-associated mice. Taken together, our data suggest that FbpA plays a role in intestinal colonization by C. difficile.
    Journal of Medical Microbiology 02/2011; 60(Pt 8):1155-61. DOI:10.1099/jmm.0.029553-0 · 2.25 Impact Factor
Show more