Good quote from one of the links.
“However, probiotic properties are strain specific and very often not well characterized. Properties of strains from the same species may be very different, thus for human health benefits potential probiotic strain should be very well characterized. It is clear that microflora of the human body is very complex and it is important to maintain appropriate homeostasis, which may be unbalanced by use of antibiotics”
—-Human microflora is very complex and become extremely challenging once it is severely out of balance.—–