Probiotics may protect their host from pathogens by producing metabolites which inhibit the colonization/growth of other microorganisms or by competing with them for resources such as nutrients or space (Ouwehand et al., 1999; Ouwehand et al., 2001; Forestier et al., 2001; Pinchuk et al., 2001; Mukai et al., 2002; Fiorillo et al., 2002; Servin and Coconnier, 2003; Vine et al., 2004a, b).