Characterization of a toxin A-negative, toxin B-positive strain of Clostridium difficile

Abstract

This study was undertaken to examine toxin production by Cltidium diWjcile 8864, a naturally occurring isolate that has been reported to produce toxin B in the absence of toxin A. To date, this is the only strain of C. difficile reported to produce only one of the toxins. The results of our initial studies with antibodies against toxins A and B confirmed these observations. Toxin B from strain 8864 and from VPI strain 10463, a strain that produces high levels of both toxin A and toxin B, was purified to homogeneity by sequential anion-exchange chromatography on DEAE-Sepharose CL-6B, gel filtration on Ultrogel AcA22, and immunoadsorption chromatography, and their toxic activities were compared. Our results showed that toxin B from strain 8864 and toxin B from C. dificile VPI strain 10463 were comparable in their cytotoxic activities and that the 8864 toxin B was more lethal. In addition, we observed that toxin B from strain 8864 was weakly enterotoxic, which may explain the ability of this strain to cause intestinal disease in hamsters treated with antibiotics. Analysis with specific antibodies showed that the toxin B molecules from these strains were highly related but contained distinct epitopes. The results of hybridization studies with probes specific for the toxin B gene of VPI strain 10463 demonstrated differences between the toxin B genes of the two strains. In addition, probes specific for the toxin A gene of VPI strain 10463 showed that strain 8864 contains a region which shows identity with the S' end of the toxin A gene but not the region of the gene which encodes a hydrophobic region and the repeating units.

Novel Molecular Type ofClostridium difficilein Neonatal Pigs, Western Australia

“…All mice infected with strain M7404 died (Figure 2 than did the ribotype 078 strain JGS6133 (p = 0.0011 by analysis of variance) (Figure 2, panel B). This difference may be the result of production of a variant toxin; similar toxins were 8-fold more toxic to mice than was toxin B produced by strain VPI10463 (15).…”

Heterogeneity of large clostridial toxins: importance ofClostridium difficiletoxinotypes

“…In contrast, for TcdB some immunological differences were observed. TcdBs produced by A À B1 toxinotypes VIII (serogroup F) and X did not react with some mAbs specific for the reference toxin TcdB VPI10463 (Lyerly et al, 1992;Depitre et al, 1993). LCTs can result in two types of cytopathic effects (Fig.…”

“…A À B1 toxinotypes A À B1 strains were the first well-characterized variant strains of C. difficile (Borriello et al, 1992;Lyerly et al, 1992;Depitre et al, 1993). There are currently four known toxinotypes exhibiting the A À B1 phenotype: VIII, X, XVI A À B1CDT À VIII some 0-like strains A À : nonsense mutation at aa position 47 in tcdA gene A À : mechanism unknown A À B1CDT1 X XVI, XVII, some V-like strains A À : rearrangement in PaLoc and large deletion causing probably changes in regulation and low or no transctiption of truncated tcdA A À : mechanism unknown A1B À CDT1 IX-like B À : mechanism unknown A À B À CDT1 XIa, XIb some strains without PaLoc A À , B À : only small nonfunctional part of PaLoc present A À B À : no PaLoc A À B À CDT À PaLoc and CDT locus negative strains (Table 2).…”

Transcription Analysis of the Genes tcdA‐E of the Pathogenicity Locus of Clostridium Difficile

“…Some strains were reported to be deficient in TcdA production while still producing TcdB (Torres, 1991). This phenomenon could in part be explained by the observation of deletions within their tcdA genes (Lyerly et al, 1992;Depitre et al, 1993). However, some of the deficient strains were inactive in the hamster model (DelmCe and Avesani, 1990) while others were as potent as the laboratory strain C. dificile VPI10463 (Torres, 1991).…”