2.3. Faecal indicator bacteria (FIB) detection
For FIB detection, 100 mL of each sample was collected in parallel
from all sites. All samples were kept on ice and processed
within 24 h. The enumeration of EC was carried out in a 96-well
microplate (MUG/EC 355-3782, BioRad, Barcelona, Spain®) according
to ISO 9308-2:2012 using the most probable number
(MPN) procedure (Donovan et al., 1998) to detect EC based on the
expression of the enzyme b-D-glucuronidase present in most EC
strains. Intestinal enterococci were also quantified by MPN in a 96-
well microplate (MUG/EC 355-3783, BioRad®) following the ISO
7899-1:1998 procedure based on the detection of the expression of
the b-glycosidase enzyme characteristic of enterococci.