the highest diversity index, and the ST121 allelic profile was represented
by a major number of isolates.
A high genetic diversity (D ¼ 84.01%) was observed among
L. monocytogenes isolates (17 different STs out of 106 isolates). This
degree of diversity is common in meat processing environments
Differences in diversity were
observed among plants. Thevenot et al. (2006a) obtained higher
diversity in large plants and explained this fact by the heterogeneity
of the raw material and the higher quantity of raw meat used
by these factories.
A wide distribution of some STs, mainly ST9 and ST121, was
observed. Both ST9 and ST121 included isolates from several
different plants that are geographically dispersed throughout
Spain. Moreover, these STs have also been recovered in RTE meat
products from 1994 to 2011, demonstrating its persistence through
the years. ST9 and ST121 strains have also been reported in several
European countries from different environmental, clinical and food
sources