6.2. FISH after non-cultural enrichment
A wide variety of different separation processes for bacteria in
complex matrices have been developed, which are not only useful
for FISH, but also for other rapid techniques or to enhance the ca-
pacity of cultivation methods (Brehm-Stecher et al., 2009; Stevens
and Jaykus, 2004). For the isolation and concentration of the target
organism the different physical, chemical and biological properties
of a bacterial species or the adsorbance on specific materials can be
employed (Brehm-Stecher et al., 2009). Approaches to concentrate
the target organisms vary substantially in their specificity and costs.
These methods should be chosen carefully because some rather
target-unspecific techniques like filtration and centrifugation steps
might also concentrate interfering substances and particles which
can complicate subsequent analyses (Stevens and Jaykus, 2004).
Commercially available systems which can specifically separate
microbes from other parts of the sample already exist; some of
them have the potential to be used for a broad range of food
matrices (Pathatrix, Dynabeads and others). In contrast to DNA
extraction methods, in which rather harsh conditions might be
applied, enrichment procedures for FISH analyses have to be per-
formed with much more caution to maintain the cell integrity.