Results are expressed as the mean and standard deviation error
mean (SEM) of three independent experiments with duplicate
determinations. Differences were considered statistically signi
fi
-
cant at p
<
0.05. In order to correlate the origin of the 177 strains
with their ability to resist to low pH and to tolerate different bile
salt concentrations, data obtained were subjected to principal
component analysis (PCA) using the statistical software Statistica
for Windows (Statistica 6.0 per Windows 1998, StatSoft, Vigonza,
Italia)