*3.2. Healthy Carriers*

Asymptomatic colonization of *C. difficile* without any signs of disease has been described in many studies on both human beings and animals [39].

The literature suggests that the range of intestinal *C. difficile* colonization of healthy adults can rate from 2.4% to 17.5% [40], and it can be associated with the composition of intestinal microbial communities but also with other extrinsic factors, such as the living environment as well as the host immune state.

Ozaki et al. reported that *C. difficile* colonization was relatively common among healthy individuals. A healthy asymptomatic carrier has no major difference regarding the gut microbial community compared to a healthy subject. Therefore, Rea MC et al. suggested that the commensal flora in such subjects could protect the host by preventing potentially pathogenic *C. difficile* colonization, multiplication, and toxin production [41].

However, unlike a healthy person with a negative culture, the carrier subject can develop CDI because of the changes in the microbiome that may contribute and favor the growth of the microbe and eventually CDI such as antibiotic treatment, diet, age, host immune state, environment, and hospital admission.

The presence of *C. difficile* in healthy carriers is one of the most important pieces of evidence of one of the many roles played by normal commensal flora.

In this case, the microbiome performs its physiological and essential immune regulatory function, thus succeeding in curbing even a dreaded condition such as *CDI*.
