Listeria species isolation
The ISO 11290-1 method for enrichment of Listeria was used for
samples taken in this study, and all Listeria species detected were
included in the subsequent analysis (ISO, 2002). Brilliance Listeria
chromogenic agar (Oxoid, UK), RAPID’L.mono agar (Bio-Rad, UK),
and Oxford Listeria selective agar (Oxoid, UK) were used to plate
enriched samples, and presumptive Listeria isolates were
confirmed using the Microbact Listeria identification system
(Oxoid, UK). Four Listeria species were tested from every positive
sample, to account for (possible) strain diversity in individual
samples. All samples were processed in the laboratory on the same
day they were sampled.