Currently, many researchers have assessed the functions
of different probiotics. Also, several kinds of associated
bacteria such as Lactobacillus, Bifidobacterium,
Streptococcus, Saccharomyces and Enterococcus species etc.
in the form of probiotic products. However, the effects of
these probiotic products are variable. The variability of
results may be associated with strain differences, dose level,
storage condition, diet composition, feeding strategy and
interactions with drugs (Chesson, 1994).