Fraser Secondary Enrichment HiCynthâ„¢ Broth Base is recommended for the isolation, cultivation and enrichment of Listeria monocytogenes from food and environmental specimens. The medium is recommended by APHA. Fraser Secondary Enrichment Broth Base is formulated so as to provide optimum conditions for the growth of Listeria. This medium is prepared by replacing animal and vegetable peptones with chemically defined peptones to avoid BSE/TSE risks associated with animal peptones