deranged immunity and gut microbiome are thought to play a
crucial role [8e10].
The changing epidemiology of CDI observed over the past
decade seems to be attributable in part to the emergence of new
virulent variants, in particular the global spread of C. difficile ribotype
027 (sometimes called “hypervirulent strain”, also known as
NAP1/BI) [11]. C. difficile ribotype 027 is associated with severe
disease and increased mortality among episodes of CDI [12,13] and
have also been linked to higher recurrence rates [14].
Current understanding of the innate and acquired immune
system in CDI is rapidly expanding, and the effect of acquired
immunosuppression on the host response to C. difficile remains an
active area of research. In particular, the role of humoral immunity
against toxins A and B in preventing primary and recurrent CDI has
been established in several clinical studies [10,15,16] and has led to
novel therapeutic interventions [17].
Immunosuppressed patients are now recognized as contributing
to the changing epidemiology of CDI with a growing segment
of the population having significant defects in the immune system.
Indeed, the total number of hematopoietic stem cell transplantations
(HSCT) increased by 50% in Europe over the last 10
years with over 35,000 recorded in 2011 [18], whereas in the US
solid organ transplantations increased from 12,623 in 1988 to