Many in vitro tests are performed when screening for potential
probiotic strains. The ability to adhere to the intestinal mucosa is
one of the more important selection criteria for probiotics
because adhesion to the intestinal mucosa is considered to be a
prerequisite for colonization (5). As substrata, enterocyte-like
Caco-2 tissue culture cells and intestinal mucus are currently
used. However, these represent only a distinct part of the intestinal
mucosa. In this respect, mucus-secreting HT29-MTX tissue
culture cells would come closer to the true situation in the intestine.
In addition to these models, human ileostomy glycoproteins
have been used to study adhesion to the small-intestinal mucosa
(6). All of these in vitro systems provide valuable information on
the ability of probiotics to adhere and colonize the intestine.
Adhesion to colonic or intestinal biopsy samples, if possible,
should be considered as a final in vitro adhesion test that would
be most like the in vivo situation. Not only would this be a better
approximation of the in vivo situation, it would allow for the
study of adhesion to different parts of the intestine. This is especially
important regarding immune stimulation by oral administration
of probiotics.