The presence of S. maltophilia in agricultural soils could
also be the consequence of anthropogenic activities such as
irrigation with wastewater or fertilization with animal-derived
products. We then looked for the presence of S. maltophilia in
various organic amendments derived from animal farms in the
Ile de France and Rh^one-Alpes regions. As previously reported
for P. aeruginosa using the same set of samples [31],
our data showed that S. maltophilia is present in bovine and
horse manures and that composting did not eliminate S. maltophilia
cells. Furthermore, S. maltophilia was found to be
more abundant than P. aeruginosa, and able to survive in both
wet and dry manures. These observations confirmed the high
adaptability of S. maltophilia to environmental conditions.
Screening for the presence of S. maltophilia in soil that received or not organic amendment showed that no relationships
could be seen between its prevalence and the addition of
manures, since soils that did not receive manure (i.e. control
soil from Feucherolles, Pierrelaye and Tunisian soils) showed
a high abundance of that species. Unfortunately, at the time of
sampling, we did not have the opportunity to look for the
presence of S. maltophilia in wastewater or sewage sludge.
However, several reports from the literature indicated that S.
maltophilia can be recovered from these waste samples. As
Tunisian sites and Pierrelaye soils were irrigated with wastewater
from municipal treatment plants or received sewage
materials as organic amendments, it would be expected that S.
maltophilia in these soils originated from exogenous sources.
As abundance could not be directly related to irrigation or
organic amendment, a diversity study would need to be performed
in order to determine whether detected populations in
soils are indigenous or originate from exogenous sources.