Clostridium perfringens iota-toxin consists of two separate proteins identified as a cell binding protein, iota b (Ib), which forms high-molecular-weight complexes on cells generating Na ؉ /K ؉ -permeable pores through which iota a (Ia), an ADP-ribosyltransferase, presumably enters the cytosol. Identity of the cell receptor and membrane domains involved in Ib binding, oligomer formation, and internalization is currently unknown. In this study, Vero (toxin-sensitive) and MRC-5 (toxin-resistant) cells were incubated with Ib, after which detergent-resistant membrane microdomains (DRMs) were extracted with cold Triton X-100. Western blotting revealed that Ib oligomers localized in DRMs extracted from Vero, but not MRC-5, cells while monomeric Ib was detected in the detergent-soluble fractions of both cell types. The Ib protoxin, previously shown to bind Vero cells but not form oligomers or induce cytotoxicity, was detected only in the soluble fractions. Vero cells pretreated with phosphatidylinositol-specific phospholipase C before addition of Ib indicated that glycosylphosphatidyl inositol-anchored proteins were minimally involved in Ib binding or oligomer formation. While pretreatment of Vero cells with filipin (which sequesters cholesterol) had no effect, methyl-␤-cyclodextrin (which extracts cholesterol) reduced Ib binding and oligomer formation and delayed iota-toxin cytotoxicity. These studies showed that iota-toxin exploits DRMs for oligomer formation to intoxicate cells.

We have found that lethal toxin from Clostridium sordellii, which specifically inactivates the low molecular weight G proteins Ras, Rap, and Rac, inhibits the activation of p38 mitogen-activated protein kinase (

Several different nomenclatures have been applied to the Clostridium difficile toxins and their associated genes. This paper summarizes the new nomenclature that has been agreed to by the research groups currently active in the field. The revised nomenclature includes C. difficile toxins and other related large clostridial toxins produced by Clostridium sordellii and Clostridium novyi, and corresponding toxin genes, as well as toxin production types of C. difficile strains.

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Four cases of botulism, linked to consumption of contaminated halal sausage