Anucha Apisarnthanarak, Linda M. Mundy

Severe morbidities and fatalities due to Clostridium difficile are usually rare. The emergence of hypervirulent strains containing binary toxin (toxinotype III, ribotype 027), mutation in tcdC variants, high-level toxin A and B production in clinical isolates together with the evolution of a C. difficile strain with high-level resistance to the newer quinolones (i.e. gatifloxacin and moxifloxacin) have contributed to the rise in C. difficile-associated diarrhea (CDAD) disease severity and mortality in recent years. Metronidazole or vancomycin is regarded as initial CDAD therapy, although several adjunctive strategies have been introduced to treat severe infection. Our current understanding of CDAD suggests that further characterization of virulence is imperative in order to effectively optimize CDAD treatment and prevention strategies. (J Infect Dis Antimicrob Agents 2007;24:151-62.)