SummaryProgress towards understanding the molecular basis of virulence in Clostridium difficile has been hindered by the lack of effective gene transfer systems. We have now, for the first time, developed procedures that may be used to introduce autonomously replicating vectors into this organism through their conjugative, oriT -based mobilization from Escherichia coli donors. Successful transfer was achieved through the use of a plasmid replicon isolated from an indigenous C. difficile plasmid, pCD6, and through the characterization and subsequent circumvention of host restriction/modification (RM) systems. The characterized replicon is the first C. difficile plasmid replicon to be sequenced and encodes a large replication protein (RepA) and a repetitive region composed of a 35 bp iteron sequence repeated seven times. Strain CD6 has two RM systems, Cdi CD6I/M .Cdi CD6I and Cdi CD6II/M. Cdi CD6II, with equivalent specificities to Sau 96I/M.

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The benefit of adding rituximab to standard treatment in nonsplenectomized patients with primary immune thrombocytopenia (ITP) is uncertain. We performed a pilot randomized trial to determine the feasibility of recruitment, protocol adherence, and blinding of a larger trial of rituximab versus placebo; and to evaluate the potential efficacy of adjuvant rituximab in ITP. Nonsplenectomized adults with newly diagnosed or relapsed ITP who were receiving standard ITP therapy for a platelet count below 30 ؋ 10 9 /L were randomly allocated to receive 4 weekly infusions of 375 mg/m 2 rituximab or saline placebo. Sixty patients were recruited over 46 months, which was slower than anticipated. Protocol adherence and follow-up targets were achieved, and blinding was successful for research staff but not for patients. After 6 months, there was no difference between rituximab and placebo groups for the composite outcome of any platelet count below