Dear Debashish,

Please read the following text which was taken from a publication contained in the link depicyed at the end of this answer:

When discussing probiotics, the term “human strains” is a rather vague one. It typically refers to a probiotic strain that is derived from the human body.

The scientific definition of a probiotic (Live microorganism which when administered in adequate amounts confers a health benefit on the host) does not stipulate that to be a probiotic the microbe must have a human origin, or be a “human strain”. Probiotics must be able to exert their benefits on the host through growth and/or activity in the human body (Collins et al., 1998; Morelli, 2000). It is therefore the action, and not the source of the probiotic microorganism that is a key factor in choosing a probiotic. The ability of a probiotic strain to remain viable at the target site and to be effective in the human gut should always be verified and tested.

There are in fact many examples of effective probiotic strains which are not recognised as normal residents of the human gastrointestinal tract. For example, no strain of Saccharomyces boulardii could be described as a “human strain”, and yet this species has been shown in numerous clinical trials to benefit human consumers.There is absolutely no existing scientific evidence that human strains are more capable of binding than non human strains. As “human strains” tend to come from the human faeces, this fact in itself acts as evidence of their capability to survive intestinal transit; a key factor when considering a good probiotic. It does not, however, provide evidence that they can adhere to or colonize the human gut more effectively than a strain which is not considered to be of human origin.

At OptiBac we do not therefore consider the the question of “human strain” to be a relevant criterion for selecting an effective probiotic.

However, for those of you who are still curious, here is a list of our probiotic strains and their specific origins:

Dairy Origin:

Lactobacillus acidophilus Rosell-52

Lactobacillus casei Rosell-215

Lactobacillus paracasei Lpc-37

Lactobacillus rhamnosus Rosell-11

Lactococcus lactis Rosell-1058

Bifidobacterium bifidum Rosell-175

Human Origin:

Lactobacillus acidophilus NCFM®

Lactobacillus acidophilus UBLA 34

Lactobacillus reuteri RC-14®

Lactobacillus rhamnosus GR-1®

Bifidobacterium bifidum Bb-02

Bifidobacterium bifidum Rosell-71

Bifidobacterium breve Rosell-70

Bifidobacterium breve UBBBr-01

Bifidobacterium infantis Rosell-33

Bifidobacterium infantis UBBI-01

Bifidobacterium lactis Bi-07

Bifidobacterium lactis Bl-04

Bifidobacterium longum UBBL 64

It's worth bearing in mind that the strains of bacteria used in probiotic food supplements are not directly sourced from human faecal samples; they will just be strains that were originally extracted during the early research into probiotics from healthy human stool samples. Representatives from these strains have then been stored in microbiology banks, and from these original samples, new bacteria can be cultured under laboratory conditions using an appropriate fermentation medium such as dairy, soy, barley or other foodstuff.

http://www.optibacprobiotics.co.uk/live-cultures/articles/what-are-human-strains

Hoping this will be helpful,

rafik

Lactobacilli have been much studied and the taxonomy is comparatively well

developed. The subgeneric classification proposed by Rogosa & Sharpe (1959),

with its revival of the species groups recognized by Orla-Jensen

(1919), incorporates most of the recent taxonomic ideas about the genus.

So Lactobacilli is a gut symbiont colonizing stratified squamous epithelia in the upper intestinal tract of animals and is a stable part of colonic and vaginal microbiota of humans (17, 29, 31). 

Find another details about specie as Lactobacillus reuteri  in the following publication:

Intestinal Origin of Sourdough Lactobacillus reuteri Isolates as Revealed by Phylogenetic, Genetic, and Physiological Analysis.  Marcia Shu-Wei Sua,, Phaik Lyn Ohb, Jens Walterb and Michael G. Gänzle.  Appl. Environ. Microbiol. September 2012 vol. 78 no. 18 6777-678.

Thank you

Marius